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Daneshvar M, Yadegari A, Hasanzadeh M, Djafarian K. Evaluation of Selenium Status among Iranian Pregnant Women: A Systematic Review and Met-Analysis. JNFS 2023; 8 (2) :306-324
URL: http://jnfs.ssu.ac.ir/article-1-467-en.html
URL: http://jnfs.ssu.ac.ir/article-1-467-en.html
Department of Clinical Nutrition, Tehran University of Medical Sciences, Tehran, Iran
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Mojtaba Daneshvar; MSc1,3, Anahita Yadegari; BS2,3, Mohaddeseh Hasanzadeh; MSc3 &
Kurosh Djafarian; PhD*1
1 Department of Clinical Nutrition, School of Nutritional Sciences and Dietetics, Tehran University of Medical Sciences, Tehran, Iran; 2 Department of Nutrition, Science and Research Branch, Islamic Azad University, Tehran, Iran, Iran; 3 Universal Scientific Education and Research Network (USERN), Tehran, Iran.
Introduction
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Evaluation of Selenium Status among Iranian Pregnant Women: A Systematic Review and Met-Analysis
Mojtaba Daneshvar; MSc1,3, Anahita Yadegari; BS2,3, Mohaddeseh Hasanzadeh; MSc3 &
Kurosh Djafarian; PhD*1
1 Department of Clinical Nutrition, School of Nutritional Sciences and Dietetics, Tehran University of Medical Sciences, Tehran, Iran; 2 Department of Nutrition, Science and Research Branch, Islamic Azad University, Tehran, Iran, Iran; 3 Universal Scientific Education and Research Network (USERN), Tehran, Iran.
| ARTICLE INFO | ABSTRACT | |
| SYSTEMATIC REVIEW and META-ANALYSIS | Background: Selenium (Se) plays an important role in numerous immunological functions of human health. It has been shown that maternal Se deficiency contributes to many pregnancy complications such as pre-eclampsia, gestational diabetes mellitus (GDM), miscarriage, and even fetal growth restriction. Due to the evidence of importance of Se in pregnancy outcomes and the inconsistency of current shreds of evidence on Se adequacy in Iranian pregnant women, this study aimed to provide a comprehensive evaluation of published studies. This systematic review explored studies reporting dietary Se intake, serum or plasma Se, and Umbilical cord Se in Iranian pregnant women. Methods: PubMed, Scopus, Web of Science, Embase, Google scholar (in English and Persian), and Persian databases, including Scientific Information Database, IranDoc, Iranian National Library, Magiran, and Regional Information Center for Science and Technology, were reviewed. Results: A total of 30 studies were included in the meta-analysis. Pooled effect sizes show an overall value of 90.09 µg/l (95% CI: 81.89, 98.29) and 75.08 µg/d (95% CI: 63.01, 87.16) for serum and dietary Se. Geographically, the lowest serum Se was in Fars and East-Azerbaijan with values of 61.97 µg/l (51.38, 72.55) and 55.12 µg/l (48.5, 61.74), respectively. Dietary intake pooled estimate showed that the lowest Se intake was in West-Azerbaijan with a value of 42.80 µg/d (95% CI: 38.95, 46.65). Conclusion: The current study shows that the overall serum and dietary intake of Se in Iranian pregnant women is acceptable. Some parts of the country need monitoring to prevent Se inadequacy and related-adverse complications in pregnant women. Keywords: Iran; Pregnancy; Pregnancy complications; Selenium; Systematic review |
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| Article history: Received: 28 Aug 2021 Revised:1 Jan 2022 Accepted: 5 Jan 2022 |
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| *Corresponding author kdjafarian@tums.ac.ir Department of Clinical Nutrition, School of Nutritional Sciences and Dietetics, Tehran University of Medical Sciences (TUMS), Tehran, Iran. Postal code: 8916188637 Tel: +98 21 88955969 |
Introduction
Selenium (Se) as an essential trace element, has attracted great attention due to its several roles in human health. Among the wide variety of functions in the body, Se has a structural role in enzymatically active proteins called selenoproteins, including Glutathione peroxidases (GPx), thioredoxin reductases, and deiodinases (Rayman, 2000, 2012). Selenoproteins are well-known for their Reactive Oxygen Species (ROS) scavenging activity, which may interpret Se importance in pregnancy, especially because of increased ROS production during this period (Pieczyńska and Grajeta, 2015, Zachara, 2018). The placenta has been considered the main source of oxidative stress during pregnancy, and accumulation of ROS during placental development can be exacerbated by Se insufficiency. On the other hand, increasing mass of erythrocytes in the fetus, and increased oxygen demands in the body of a mother may alter Se homeostasis during pregnancy (Kyozuka et al., 2021, Pieczyńska and Grajeta, 2015). ROS agglomeration, as a consequence of inadequate maternal Se concentration and/or impaired antioxidant defense, may lead to different pregnancy complications such as pre-eclampsia (PE), gestational diabetes mellitus (GDM), preterm birth, and abortion. These conditions can threaten maternal and neonatal health (Kyozuka et al., 2021, Mariath et al., 2011).
Se exposure has been assessed in epidemiologic studies through several biomarkers, including its concentrations in erythrocyte, whole blood, serum or plasma (Sieniawska et al., 1999), and also hair and toenail (Filippini et al., 2017). Serum and plasma Se reflect short-term status; nonetheless, they are the most commonly used indicators in pregnant women (Stoffaneller and Morse, 2015). Some studies also evaluated Se status in pregnancy by measuring dietary intake (Kyozuka et al., 2021, Solé-Navais et al., 2021) or urinary Se (Koukkou et al., 2014). Sufficient plasma concentration of Se is estimated by reaching optimal plasma GPX activity, which is achieved at approximately 90 μg/l (Duffield et al., 1999, Kipp et al., 2015); however, the lower limit of 70 μg/l (0.89 μmol/l) has been reported due to obtaining normal Se levels (Okunade et al., 2018); the latter has been suggested to prevent GDM (Liu et al., 2021).
Studies on dietary Se intakes have demonstrated that Se intake varies markedly worldwide ranging from approximate values of 7-30 μg/d in Eastern European countries and some parts of China to even toxic amounts with an approximate value of 5 mg/d resulting in selenosis (Rayman, 2008). Dietary Se intake in Europe has been estimated as 30 μg/d, while in the U.S., the intake is more than 90 μg/d (Kieliszek, 2019). This variation in dietary intake of Se mainly depends on the concentration of Se in soils (Al-Othman et al., 2012), moreover, other factors such as geochemistry, rainfall, and dietary habits can affect total Se intake. The main food sources of Se in diet are cereals, organ meat, and fish (Chun et al., 2010, Solé-Navais et al., 2021), followed by eggs and dairy products (Solé-Navais et al., 2021). Considering the Se concentration in food crops and soil, Se rich fertilizers can improve its concentration in soils where plants and animals are produced as food (Al-Othman et al., 2012, Nazemi et al., 2012). In 2010, Xia et al. indicated that 49 μg/d Se is desired to obtain selenoprotein P saturation in Se-deficient Chinese subjects (Xia et al., 2010). In 2015, joint nutrition societies of Germany, Austria, and Switzerland revised the reference value to 60 μg/d in adult women (Kipp et al., 2015); finally, in 2019, the European Food Safety Authority recommended 70 μg/d Se in pregnancy (Hubalewska-Dydejczyk et al., 2020). Se status expansively varies throughout middle eastern countries, since suboptimal and supra-optimal Se status has been reported in parts of Saudi Arabia and Jordan, respectively (Ibrahim et al., 2019). However, between-population variation is also noticeable, where the Se status in the North-Western population (Tabriz), is considerably lower than North-Eastern (Mashhad) in Iran (Vanderlelie and Perkins, 2011).
Given the remarkable role of Se in health and complications related to pregnancy, there is a need to have a comprehensive assessment of the current status of Se among Iranian pregnant women. Therefore, the present study aimed to estimate the Se status in different provinces of Iran.
Materials and Methods
The current study was conducted based on
the guidelines of the Preferred Reporting Items for Systematic Reviews and Meta‐Analysis (PRISMA) statement (PRISMA statement).
Search strategy and data collection: Searching was performed up to 3 May 2021 and the following databases were searched: PubMed, Scopus, Web of Science, Embase, and google scholar (in English and Persian), along with Persian databases including Scientific Information Database (SID) (http://www.sid.ir/), Iranian Research Institute for Information Science and Technology (IranDoc) (https://irandoc.ac.ir), Iranian National Library (http://www.nlai.ir/), Magiran (http://www.magiran.com/), and Regional Information Center for Science and Technology (RICST) (http://en.ricest.ac.ir/).
The following medical subject heading terms and words were used for the search: ("selenium" OR Microelement OR "trace element" OR micronutrient OR minerals OR antioxidant OR selenium OR selen* OR selepen OR organoselen* OR natriumselen* OR methylseleninic OR methylselenium OR selenomethionin* OR selenite* OR selenate*) AND (Iran OR Iranian) AND (maternal OR prenatal OR peripartum OR pregnancy OR premature OR preterm OR preeclampsia OR "intrauterine growth restriction" OR "Pregnancy" OR pregnant OR gestational OR gestation* OR gravid OR preconception* OR conception OR miscarriage OR abortion). No country or study type limitation was applied. Finally, the reference list of eligible articles was checked for related studies.
Study selection: The inclusion criteria were determined as follows: 1) Studies on the Iranian population living in Iran; 2) Pregnant women with or without gestational and or delivery complications in mother or neonate; 3) evaluation Se in maternal serum, plasma, dietary intake, or in umbilical cord serum; and 4) Estimating overall Se status in Iranian pregnant women. The exclusion criteria were as follows: 1) Non-Iranian subjects; 2) Non-pregnant subjects; 3) insufficient statistical data; 4) unavailable full-text; and 5) duplicate data.
Data extraction: Data extraction was performed independently by one author (Daneshvar M) and was checked by another author (Hasanzadeh M) to reach more accuracy. The information was extracted including the author’s name, publication year, study design, characteristics of the participants (maternal age, gestational age, health conditions, province and city, and sample size), mean and standard deviation (SD)/or standard error (SE) of Se level. Conversion of units and statistical values of measurements were performed accordingly, using Cochrane methods.
Quality assessment: The risk of bias (RoB) assessment tool for non-randomized studies (RoBANS) was used to evaluate the quality of observational studies. RoBANS contains six domains including selection, performance, detection, attrition, and reporting bias. RoB for each domain was categorized as low, high, or unclear (Kim et al., 2013). For interventional trials, RoB was assessed in each study using the Cochrane RoB assessment tool which assesses sequence generation, allocation concealment, blinding of participants and personnel, blinding of outcome assessments, incomplete outcome data, and selective outcome reporting (Higgins et al., 2011).
Data analysis: Meta-analyses were performed using random-effects models based on mean and standard error. For studies that reported a standard deviation, the standard error was calculated using relevant formulas (Higgins and Deeks, 2011). Moreover, for two studies with missing standard deviation, appropriate values were imputed from the nearest studies, using the Furukawa method (Higgins and Green, 2019). In two studies, plasma Se was reported, and they were considered as serum levels due to non-noticeable differences (Johnson et al., 2010, Stoffaneller and Morse, 2015). Heterogeneity between the studies was evaluated by the Cochrane Q test and I2 statistic, with values greater than 50%, indicating substantial heterogeneity (Higgins and Thompson, 2002).{Higgins, 2002 #78} Subgroup analyses were carried out to find probable sources of heterogeneity, according to the predefined variables including health condition, province, year, trimester, maternal age, maternal body mass index (BMI ), language, and study design. Egger’s linear regression and Begg’s test were used to evaluate the publication bias (Lin and Chu, 2018), with P-values < 0.05 were considered significant. Sensitivity analysis was also achieved to evaluate the impact of each study, based on the results of the overall serum Se. All statistical analyses were conducted by the use of the STATA, version 11.2 (StataCorp). A P-value < 0.05 was considered a significant level.
Results
Study selection: A total of 437 articles were identified through an initial search, and following the removal of duplicates, the title and abstracts of 251 articles were screened. By skimming the title and abstracts, 136 articles were excluded due to irrelevancy in context (animal/cell study, review, gene study, etc.). After evaluating full-text of the remaining studies, 85 papers were excluded based on pre-defined criteria, and eventually, 30 studies (Aalami-Harandi et al., 2015, Akhlaghi et al., 2012, Alipour et al., 2015, Asemi et al., 2015, Asemi et al., 2012, Atarod et al., 2015, Boskabadi et al., 2012, Daneshzad et al., 2020, Davaryari et al., 2011, Farzin and Sajadi, 2012, Ghaemi et al., 2013, Iranpour et al., 2009, Jalili et al., 2015, Kazemian et al., 2013, Khoigani et al., 2012, Kooshki et al., 2009, Kushki et al., Maleki et al., 2011, Mazloomi et al., 2021, Mohammadzadeh et al., 2009, Mohammadzadeh et al., 2012, Monafi et al., 2003, Moshfeghy et al., 2020, Mostafa-Gharehbaghi et al., 2012, Nazemi et al., 2015, Noormohammadi Isa et al., 2004, Parast and Paknahad, 2017, Peirovifar et al., 2013, Sheykhi et al., 2015, Tara et al., 2010b) were included in the meta-analysis (Figure 1).
Characteristics of the included studies: The included studies were published between the year 2004 to 2020. Study designs included RCT, cohort, cross-sectional, and case-control studies. Health conditions in women and neonates differed across studies including healthy, PE, GDM, and abortion for women and healthy, low birth weight (LBW), and preterm labor for neonates.
Fifteen studies reported the serum Se status of 1381 women in 8 provinces (1245 pregnant women during gestation and 136 women at the time of delivery). Dietary Se intake was evaluated between 2512 pregnant women in 5 provinces. Also, 523 umbilical cord serum Se was measured in 6 studies from 4 provinces. The total number of participants in the umbilical cord, dietary intake, and serum Se evaluation studies ranged from 19-177, 44-584, and 38-125, respectively. Se status was measured mostly using atomic absorption spectrometry in sera. Food frequency questionnaire (FFQ), food recall, and dietary record were used for a dietary intake assessment. Detailed study characteristics are illustrated in Table 1. The quality of the included studies is provided in Table 3. The overall score was evaluated by the number of domains, in which low RoB was determined. Only one study had a high RoB (overall score =< 2), and 12 studies were found with low RoB (overall score = 6). The remaining 17 papers presented moderate quality (overall score 3 to 6).
Meta-analysis results
Serum Se: Thirty effect-sizes with a total sample size of 1245 participants were included in the Meta-analysis using a random-effect model. The overall mean serum Se concentration in the Iranian pregnant population during gestation was 90.09 μg/l (95% CI: 81.89, 98.29 μg/l), with significant heterogeneity between studies (P < 0.001, I2=98.8). Reported values varied from 39.87 μg/l in Fars province to 137.43 μg/l in Razavi Khorasan. Serum Se data was stratified into healthy (no diagnosed complication in the mother or neonate) and unhealthy (at least one diagnosed complication in the mother or neonate) groups. The combined analysis of mean serum Se concentration for a healthy group including 17 effect sizes revealed a mean value of 95.75 μg/l (95% CI: 85.72, 105.79 μg/l) and for the unhealthy group including 13 effect sizes revealed a mean value of 82.69 μg/l (95% CI: 68.38, 96.99 μg/l). Moreover, subgroup analysis by province evaluated mean serum Se values as follows: Razavi Khorasan 113.99 μg/l (95% CI: 96.67, 131.30 μg/l), Fars 61.97 μg/l (95% CI: 51.38, 72.55 μg/l), East-Azerbaijan 55.12 μg/l (95% CI: 48.50, 61.74 μg/l), Tehran 90.93 μg/l (95% CI: 82.20, 99.65 μg/l), Hamadan 94.25 μg/l (95% CI: 64.88, 123.63 μg/l), Kermanshah 87.16 μg/l (95% CI: 75.91, 98.41 μg/l), and Mazandaran 87.68 μg/l (95% CI: 68.67, 106.69 μg/l) (Figures 2, 3). Trimester subgroup analysis presented mean values of 90.42 μg/l (95% CI: 57.54, 123.29 μg/l) for the first trimester, 87.68 μg/l (95% CI: 68.67, 106.69 μg/l) for the second trimester, and 91.20 μg/l (95% CI: 80.07, 102.33 μg/l) for the third trimester. Subgroup analysis for serum Se was also performed based on the trimester of pregnancy, maternal age (<26 and >26 years old), maternal BMI (<26 and >26 kg/m2), language (English and Persian), year of publication (=<2012, >2012), and study design (Table 2).
Meta-analysis of serum Se at delivery was fulfilled separately from maternal Se during pregnancy. The overall analysis of 4 effect sizes from 2 studies revealed a mean serum Se concentration of 94.73 μg/l (95% CI: 72.78, 116.67 μg/l) at delivery with considerable heterogeneity among studies (P < 0.001, I2 = 98.3%). The studies were categorized into two groups including the healthy group combining 2 effect sizes with a mean value of 98.62 μg/l (95% CI: 62.6, 134.65 μg/l), the PE group containing 1 effect size with a mean value of 71.22 μg/l (95% CI: 65.83, 76.61 μg/l), and the preterm bearing mothers group containing 1 effect size with the mean value of 110.56 μg/l (95% CI: 104.30, 116.82 μg/l, Table 2).
Dietary Se: Combined analysis of 23 effect sizes demonstrated that the mean dietary intake of Se in the Iranian pregnant population is 75.08 μg/d (95% CI: 63.04, 87.13 μg/d, Figure 2), with a considerable between-study heterogeneity (P < 0.001, I2 = 100%). Reported values of intake ranged from 40.95 μg/d in Isfahan to 124.7 μg/d in North-Khorasan. Subgroup analysis by trimesters and the health state of participants was conducted. In trimester subgroups, there was only one study reporting first-trimester intake with the mean value of 124.70 μg/d (95% CI: 124.29, 125.11 μg/d); for second-trimester subgroup combined analysis of 3 effect sizes revealed the mean value of 43.41μg/d (95% CI: 41.16, 45.66 μg/d) and for the third-trimester subgroup combined analysis of 19 effect sizes revealed the mean value of 76.61 μg/d (95% CI: 70.60, 82.62 μg/d). Also combined analysis of 12 and 10 effect sizes for healthy and unhealthy groups, demonstrated that mean dietary intakes were 73.91μg/d (95% CI: 56.65, 91.16 μg/d) in the healthy group and 71 μg/d (95% CI: 61.90, 80.10 μg/d) in the unhealthy group (definition of groups described earlier). Also, dietary Se intake was stratified by different Provinces and revealed that mean values of intake are as follows: Isfahan with the mean value of 74.90 μg/d (95% CI: 68.10, 81.69 μg/d), Tehran with a mean value of 60.16 μg/d (95% CI: 57.34, 62.98 μg/d), West-Azerbaijan with the mean value of 42.80 μg/d (95% CI: 38.95, 46.65 μg/d), North-Khorasan with the mean value of 71.07 μg/d (95% CI: 6.83, 135.32 μg/d), and Markazi with the mean value of 114.90 μg/d (95% CI: 105.69, 124.11 μg/d, Figure 3). Additionally, subgroup analysis was performed by different trimesters and health conditions (Table 2).
Umbilical cord serum Se: The overall analysis of 11 effect sizes reporting Se concentration in umbilical cord presented the mean value of 70.98 μg/l (95% CI: 58.95, 83.02 μg/l) with significant heterogeneity between studies (P < 0.001, I2 = 97.9%). Subgroup analysis by healthy and unhealthy birth groups was conducted. The mean value in the healthy subgroup with 6 effect sizes was 72.66 μg/l (95% CI: 55.44, 89.89 μg/l) and in the unhealthy subgroup with 5 effect sizes was 68.93 μg/l (95% CI: 52.67, 85.20 μg/l). The unhealthy group contains at least one of the following conditions: bronchopulmonary dysplasia (BPD), respiratory distress syndrome (RDS), LBW, or preterm birth (Table 2).
Sensitivity analysis: The robustness of results was assessed by performing the sensitivity analysis. Based on estimates, serum Se levels may vary between 88.60 μg/l (95% CI: 80.42, 96.76) and 91.82 μg/l (95% CI: 83.89, 99.74). By excluding two studies (4 effect sizes) with some methodological or statistical errors (Akhlaghi et al., 2012, Noormohammadi Isa et al., 2004), the overall estimate altered to 86.01 μg/l (95% CI: 77.64, 94.37 μg/l). Moreover, by excluding data from Razavi Khorasan (highest values, effect sizes = 11), an overall estimate for the remaining country fell to 78.06 μg/l (95% CI: 70.04, 86.08 μg/l). After excluding RCTs (two effect-sizes from Tara et al.), the remaining observational studies revealed that overall serum Se was equal to 87.67 μg/l (95% CI: 79.82, 95.53 μg/l).
Sensitivity analysis revealed that dietary Se can extend from 73.1 μg/d (95% CI: 60.8, 85.39 μg/l) to 76.58 μg/d (95% CI: 64.22, 88.93 μg/l). Six of 23 effect sizes are from khoigani (Khoigani et al., 2012), which can affect the overall estimate; by excluding them, the overall value rose to 84.67 μg/d (95% CI: 70.59, 98.74 μg/l). After excluding RCTs (3 studies with 6 effect-sizes), the remaining observational studies revealed that overall dietary Se was equal to 61.82 μg/d (95% CI: 47.94, 75.70 μg/l).
Publication bias: Based on results from Egger and Begg’s test, publication bias among serum Se studies was significant (P < 0.001 and P = 0.005). In the case of dietary Se intake, no evidence of publication bias was found by the Egger test (P = 0.71); however, Begg’s test showed a significant bias (P = 0.04).
Se exposure has been assessed in epidemiologic studies through several biomarkers, including its concentrations in erythrocyte, whole blood, serum or plasma (Sieniawska et al., 1999), and also hair and toenail (Filippini et al., 2017). Serum and plasma Se reflect short-term status; nonetheless, they are the most commonly used indicators in pregnant women (Stoffaneller and Morse, 2015). Some studies also evaluated Se status in pregnancy by measuring dietary intake (Kyozuka et al., 2021, Solé-Navais et al., 2021) or urinary Se (Koukkou et al., 2014). Sufficient plasma concentration of Se is estimated by reaching optimal plasma GPX activity, which is achieved at approximately 90 μg/l (Duffield et al., 1999, Kipp et al., 2015); however, the lower limit of 70 μg/l (0.89 μmol/l) has been reported due to obtaining normal Se levels (Okunade et al., 2018); the latter has been suggested to prevent GDM (Liu et al., 2021).
Studies on dietary Se intakes have demonstrated that Se intake varies markedly worldwide ranging from approximate values of 7-30 μg/d in Eastern European countries and some parts of China to even toxic amounts with an approximate value of 5 mg/d resulting in selenosis (Rayman, 2008). Dietary Se intake in Europe has been estimated as 30 μg/d, while in the U.S., the intake is more than 90 μg/d (Kieliszek, 2019). This variation in dietary intake of Se mainly depends on the concentration of Se in soils (Al-Othman et al., 2012), moreover, other factors such as geochemistry, rainfall, and dietary habits can affect total Se intake. The main food sources of Se in diet are cereals, organ meat, and fish (Chun et al., 2010, Solé-Navais et al., 2021), followed by eggs and dairy products (Solé-Navais et al., 2021). Considering the Se concentration in food crops and soil, Se rich fertilizers can improve its concentration in soils where plants and animals are produced as food (Al-Othman et al., 2012, Nazemi et al., 2012). In 2010, Xia et al. indicated that 49 μg/d Se is desired to obtain selenoprotein P saturation in Se-deficient Chinese subjects (Xia et al., 2010). In 2015, joint nutrition societies of Germany, Austria, and Switzerland revised the reference value to 60 μg/d in adult women (Kipp et al., 2015); finally, in 2019, the European Food Safety Authority recommended 70 μg/d Se in pregnancy (Hubalewska-Dydejczyk et al., 2020). Se status expansively varies throughout middle eastern countries, since suboptimal and supra-optimal Se status has been reported in parts of Saudi Arabia and Jordan, respectively (Ibrahim et al., 2019). However, between-population variation is also noticeable, where the Se status in the North-Western population (Tabriz), is considerably lower than North-Eastern (Mashhad) in Iran (Vanderlelie and Perkins, 2011).
Given the remarkable role of Se in health and complications related to pregnancy, there is a need to have a comprehensive assessment of the current status of Se among Iranian pregnant women. Therefore, the present study aimed to estimate the Se status in different provinces of Iran.
Materials and Methods
The current study was conducted based on
the guidelines of the Preferred Reporting Items for Systematic Reviews and Meta‐Analysis (PRISMA) statement (PRISMA statement).
Search strategy and data collection: Searching was performed up to 3 May 2021 and the following databases were searched: PubMed, Scopus, Web of Science, Embase, and google scholar (in English and Persian), along with Persian databases including Scientific Information Database (SID) (http://www.sid.ir/), Iranian Research Institute for Information Science and Technology (IranDoc) (https://irandoc.ac.ir), Iranian National Library (http://www.nlai.ir/), Magiran (http://www.magiran.com/), and Regional Information Center for Science and Technology (RICST) (http://en.ricest.ac.ir/).
The following medical subject heading terms and words were used for the search: ("selenium" OR Microelement OR "trace element" OR micronutrient OR minerals OR antioxidant OR selenium OR selen* OR selepen OR organoselen* OR natriumselen* OR methylseleninic OR methylselenium OR selenomethionin* OR selenite* OR selenate*) AND (Iran OR Iranian) AND (maternal OR prenatal OR peripartum OR pregnancy OR premature OR preterm OR preeclampsia OR "intrauterine growth restriction" OR "Pregnancy" OR pregnant OR gestational OR gestation* OR gravid OR preconception* OR conception OR miscarriage OR abortion). No country or study type limitation was applied. Finally, the reference list of eligible articles was checked for related studies.
Study selection: The inclusion criteria were determined as follows: 1) Studies on the Iranian population living in Iran; 2) Pregnant women with or without gestational and or delivery complications in mother or neonate; 3) evaluation Se in maternal serum, plasma, dietary intake, or in umbilical cord serum; and 4) Estimating overall Se status in Iranian pregnant women. The exclusion criteria were as follows: 1) Non-Iranian subjects; 2) Non-pregnant subjects; 3) insufficient statistical data; 4) unavailable full-text; and 5) duplicate data.
Data extraction: Data extraction was performed independently by one author (Daneshvar M) and was checked by another author (Hasanzadeh M) to reach more accuracy. The information was extracted including the author’s name, publication year, study design, characteristics of the participants (maternal age, gestational age, health conditions, province and city, and sample size), mean and standard deviation (SD)/or standard error (SE) of Se level. Conversion of units and statistical values of measurements were performed accordingly, using Cochrane methods.
Quality assessment: The risk of bias (RoB) assessment tool for non-randomized studies (RoBANS) was used to evaluate the quality of observational studies. RoBANS contains six domains including selection, performance, detection, attrition, and reporting bias. RoB for each domain was categorized as low, high, or unclear (Kim et al., 2013). For interventional trials, RoB was assessed in each study using the Cochrane RoB assessment tool which assesses sequence generation, allocation concealment, blinding of participants and personnel, blinding of outcome assessments, incomplete outcome data, and selective outcome reporting (Higgins et al., 2011).
Data analysis: Meta-analyses were performed using random-effects models based on mean and standard error. For studies that reported a standard deviation, the standard error was calculated using relevant formulas (Higgins and Deeks, 2011). Moreover, for two studies with missing standard deviation, appropriate values were imputed from the nearest studies, using the Furukawa method (Higgins and Green, 2019). In two studies, plasma Se was reported, and they were considered as serum levels due to non-noticeable differences (Johnson et al., 2010, Stoffaneller and Morse, 2015). Heterogeneity between the studies was evaluated by the Cochrane Q test and I2 statistic, with values greater than 50%, indicating substantial heterogeneity (Higgins and Thompson, 2002).{Higgins, 2002 #78} Subgroup analyses were carried out to find probable sources of heterogeneity, according to the predefined variables including health condition, province, year, trimester, maternal age, maternal body mass index (
Results
Study selection: A total of 437 articles were identified through an initial search, and following the removal of duplicates, the title and abstracts of 251 articles were screened. By skimming the title and abstracts, 136 articles were excluded due to irrelevancy in context (animal/cell study, review, gene study, etc.). After evaluating full-text of the remaining studies, 85 papers were excluded based on pre-defined criteria, and eventually, 30 studies (Aalami-Harandi et al., 2015, Akhlaghi et al., 2012, Alipour et al., 2015, Asemi et al., 2015, Asemi et al., 2012, Atarod et al., 2015, Boskabadi et al., 2012, Daneshzad et al., 2020, Davaryari et al., 2011, Farzin and Sajadi, 2012, Ghaemi et al., 2013, Iranpour et al., 2009, Jalili et al., 2015, Kazemian et al., 2013, Khoigani et al., 2012, Kooshki et al., 2009, Kushki et al., Maleki et al., 2011, Mazloomi et al., 2021, Mohammadzadeh et al., 2009, Mohammadzadeh et al., 2012, Monafi et al., 2003, Moshfeghy et al., 2020, Mostafa-Gharehbaghi et al., 2012, Nazemi et al., 2015, Noormohammadi Isa et al., 2004, Parast and Paknahad, 2017, Peirovifar et al., 2013, Sheykhi et al., 2015, Tara et al., 2010b) were included in the meta-analysis (Figure 1).
Characteristics of the included studies: The included studies were published between the year 2004 to 2020. Study designs included RCT, cohort, cross-sectional, and case-control studies. Health conditions in women and neonates differed across studies including healthy, PE, GDM, and abortion for women and healthy, low birth weight (LBW), and preterm labor for neonates.
Fifteen studies reported the serum Se status of 1381 women in 8 provinces (1245 pregnant women during gestation and 136 women at the time of delivery). Dietary Se intake was evaluated between 2512 pregnant women in 5 provinces. Also, 523 umbilical cord serum Se was measured in 6 studies from 4 provinces. The total number of participants in the umbilical cord, dietary intake, and serum Se evaluation studies ranged from 19-177, 44-584, and 38-125, respectively. Se status was measured mostly using atomic absorption spectrometry in sera. Food frequency questionnaire (FFQ), food recall, and dietary record were used for a dietary intake assessment. Detailed study characteristics are illustrated in Table 1. The quality of the included studies is provided in Table 3. The overall score was evaluated by the number of domains, in which low RoB was determined. Only one study had a high RoB (overall score =< 2), and 12 studies were found with low RoB (overall score = 6). The remaining 17 papers presented moderate quality (overall score 3 to 6).
Meta-analysis results
Serum Se: Thirty effect-sizes with a total sample size of 1245 participants were included in the Meta-analysis using a random-effect model. The overall mean serum Se concentration in the Iranian pregnant population during gestation was 90.09 μg/l (95% CI: 81.89, 98.29 μg/l), with significant heterogeneity between studies (P < 0.001, I2=98.8). Reported values varied from 39.87 μg/l in Fars province to 137.43 μg/l in Razavi Khorasan. Serum Se data was stratified into healthy (no diagnosed complication in the mother or neonate) and unhealthy (at least one diagnosed complication in the mother or neonate) groups. The combined analysis of mean serum Se concentration for a healthy group including 17 effect sizes revealed a mean value of 95.75 μg/l (95% CI: 85.72, 105.79 μg/l) and for the unhealthy group including 13 effect sizes revealed a mean value of 82.69 μg/l (95% CI: 68.38, 96.99 μg/l). Moreover, subgroup analysis by province evaluated mean serum Se values as follows: Razavi Khorasan 113.99 μg/l (95% CI: 96.67, 131.30 μg/l), Fars 61.97 μg/l (95% CI: 51.38, 72.55 μg/l), East-Azerbaijan 55.12 μg/l (95% CI: 48.50, 61.74 μg/l), Tehran 90.93 μg/l (95% CI: 82.20, 99.65 μg/l), Hamadan 94.25 μg/l (95% CI: 64.88, 123.63 μg/l), Kermanshah 87.16 μg/l (95% CI: 75.91, 98.41 μg/l), and Mazandaran 87.68 μg/l (95% CI: 68.67, 106.69 μg/l) (Figures 2, 3). Trimester subgroup analysis presented mean values of 90.42 μg/l (95% CI: 57.54, 123.29 μg/l) for the first trimester, 87.68 μg/l (95% CI: 68.67, 106.69 μg/l) for the second trimester, and 91.20 μg/l (95% CI: 80.07, 102.33 μg/l) for the third trimester. Subgroup analysis for serum Se was also performed based on the trimester of pregnancy, maternal age (<26 and >26 years old), maternal BMI (<26 and >26 kg/m2), language (English and Persian), year of publication (=<2012, >2012), and study design (Table 2).
Meta-analysis of serum Se at delivery was fulfilled separately from maternal Se during pregnancy. The overall analysis of 4 effect sizes from 2 studies revealed a mean serum Se concentration of 94.73 μg/l (95% CI: 72.78, 116.67 μg/l) at delivery with considerable heterogeneity among studies (P < 0.001, I2 = 98.3%). The studies were categorized into two groups including the healthy group combining 2 effect sizes with a mean value of 98.62 μg/l (95% CI: 62.6, 134.65 μg/l), the PE group containing 1 effect size with a mean value of 71.22 μg/l (95% CI: 65.83, 76.61 μg/l), and the preterm bearing mothers group containing 1 effect size with the mean value of 110.56 μg/l (95% CI: 104.30, 116.82 μg/l, Table 2).
Dietary Se: Combined analysis of 23 effect sizes demonstrated that the mean dietary intake of Se in the Iranian pregnant population is 75.08 μg/d (95% CI: 63.04, 87.13 μg/d, Figure 2), with a considerable between-study heterogeneity (P < 0.001, I2 = 100%). Reported values of intake ranged from 40.95 μg/d in Isfahan to 124.7 μg/d in North-Khorasan. Subgroup analysis by trimesters and the health state of participants was conducted. In trimester subgroups, there was only one study reporting first-trimester intake with the mean value of 124.70 μg/d (95% CI: 124.29, 125.11 μg/d); for second-trimester subgroup combined analysis of 3 effect sizes revealed the mean value of 43.41μg/d (95% CI: 41.16, 45.66 μg/d) and for the third-trimester subgroup combined analysis of 19 effect sizes revealed the mean value of 76.61 μg/d (95% CI: 70.60, 82.62 μg/d). Also combined analysis of 12 and 10 effect sizes for healthy and unhealthy groups, demonstrated that mean dietary intakes were 73.91μg/d (95% CI: 56.65, 91.16 μg/d) in the healthy group and 71 μg/d (95% CI: 61.90, 80.10 μg/d) in the unhealthy group (definition of groups described earlier). Also, dietary Se intake was stratified by different Provinces and revealed that mean values of intake are as follows: Isfahan with the mean value of 74.90 μg/d (95% CI: 68.10, 81.69 μg/d), Tehran with a mean value of 60.16 μg/d (95% CI: 57.34, 62.98 μg/d), West-Azerbaijan with the mean value of 42.80 μg/d (95% CI: 38.95, 46.65 μg/d), North-Khorasan with the mean value of 71.07 μg/d (95% CI: 6.83, 135.32 μg/d), and Markazi with the mean value of 114.90 μg/d (95% CI: 105.69, 124.11 μg/d, Figure 3). Additionally, subgroup analysis was performed by different trimesters and health conditions (Table 2).
Umbilical cord serum Se: The overall analysis of 11 effect sizes reporting Se concentration in umbilical cord presented the mean value of 70.98 μg/l (95% CI: 58.95, 83.02 μg/l) with significant heterogeneity between studies (P < 0.001, I2 = 97.9%). Subgroup analysis by healthy and unhealthy birth groups was conducted. The mean value in the healthy subgroup with 6 effect sizes was 72.66 μg/l (95% CI: 55.44, 89.89 μg/l) and in the unhealthy subgroup with 5 effect sizes was 68.93 μg/l (95% CI: 52.67, 85.20 μg/l). The unhealthy group contains at least one of the following conditions: bronchopulmonary dysplasia (BPD), respiratory distress syndrome (RDS), LBW, or preterm birth (Table 2).
Sensitivity analysis: The robustness of results was assessed by performing the sensitivity analysis. Based on estimates, serum Se levels may vary between 88.60 μg/l (95% CI: 80.42, 96.76) and 91.82 μg/l (95% CI: 83.89, 99.74). By excluding two studies (4 effect sizes) with some methodological or statistical errors (Akhlaghi et al., 2012, Noormohammadi Isa et al., 2004), the overall estimate altered to 86.01 μg/l (95% CI: 77.64, 94.37 μg/l). Moreover, by excluding data from Razavi Khorasan (highest values, effect sizes = 11), an overall estimate for the remaining country fell to 78.06 μg/l (95% CI: 70.04, 86.08 μg/l). After excluding RCTs (two effect-sizes from Tara et al.), the remaining observational studies revealed that overall serum Se was equal to 87.67 μg/l (95% CI: 79.82, 95.53 μg/l).
Sensitivity analysis revealed that dietary Se can extend from 73.1 μg/d (95% CI: 60.8, 85.39 μg/l) to 76.58 μg/d (95% CI: 64.22, 88.93 μg/l). Six of 23 effect sizes are from khoigani (Khoigani et al., 2012), which can affect the overall estimate; by excluding them, the overall value rose to 84.67 μg/d (95% CI: 70.59, 98.74 μg/l). After excluding RCTs (3 studies with 6 effect-sizes), the remaining observational studies revealed that overall dietary Se was equal to 61.82 μg/d (95% CI: 47.94, 75.70 μg/l).
Publication bias: Based on results from Egger and Begg’s test, publication bias among serum Se studies was significant (P < 0.001 and P = 0.005). In the case of dietary Se intake, no evidence of publication bias was found by the Egger test (P = 0.71); however, Begg’s test showed a significant bias (P = 0.04).
| Table 1. Characteristics of the included studies. | ||||||||||||
| Study | Language | Year | Province (city) |
Study design | Sample size Case/ Control |
Maternal age (years) Case Control |
Gestational age (weeks) Case Control |
Condition in Cases | Se concentration Case Control |
Sample | Unit | Se measuring method |
| Serum Se | ||||||||||||
| (Noormohammadi Isa et al., 2004) | Per | 2004 | Tehran (Tehran) | Case-control | 34/34 | Total 29.0±6.7 | ≤20 | MSCRG | 97.41±34.94 100.36±38.97 |
Serum | µg/l | AAS |
| (Iranpour et al., 2009) | Per | 2009 | Isfahan (Isfahan) | Case-control | 30/30 | 27.96±5.12 25.23±5.45 |
(Delivery) 29.93±2.52 39.51±1.05 |
PRT | 110.56±17.49 117.03±17.15 |
Serum | µg/l | GF-AAS |
| (Mohammadzadeh et al., 2009) | Eng | 2009 | Khorasan (Mashhad) | Case-control | 70/53 | 24.0±4.0 25.7±5.4 |
33.4±2.9 39.3±1.4 |
LBW | 118.8±24.5 122.5±29.3 |
Serum | µg/l | GF-AAS |
| (Tara et al., 2010b) | Eng | 2010 | Razavi-Khorasan (Mashhad) | RCT | 61/64 | 21.6±2.5 21.6±3.4 |
≤12 | HLTH | 122.5±23.2 122.9±26.9 |
Serum | µg/l | ET-AAS |
| (Davaryari et al., 2011) | Per | 2011 | Razavi-Khorasan (Mashhad) | Case-control | 35/30 | 29.69 24.33 |
28-40 | PE | 103.03±27.38 132.7±29.65 |
Serum | µg/l | AAS |
| (Maleki et al., 2011) | Eng | 2011 | east-Azerbaijan (Tabriz) | Case-control | 40/40 | 27.62±5.25 26.42±3.73 |
34-36 37-39 |
PE | 51.75±1.62 58.51±11.85 |
Plasma | µg/l | ET-AAS |
| (Akhlaghi et al., 2012) | Eng | 2012 | Razavi-Khorasan (Mashhad) | Case-control | 30/30 | 30 25 |
24-28 | GDM | 137.43 134.33 |
Serum | µg/l | AAS |
| (Farzin and Sajadi, 2012) | Eng | 2012 | Tehran (Tehran) | Case-control | 60/60 | 26.66±3.72 27.43±3.91 |
35.27±1.20 35.48±1.14 | PE | 88.2±21 104.7±27.8 |
Serum | µg/l | GF-AAS |
| Ghaemi et al. (Ghaemi et al., 2013) | Eng | 2013 | Fars (Shiraz) | Case-control | 38/38 | 28.4±3.13 28.2±3.12 |
25.4±1.34 24.52±1.23 |
PE | 70.63±21.41 82.03±15.54 |
Plasma | µg/l | GF-AAS |
| (Alipour et al., 2015) | Per | 2014 | Kermanshah (Kermanshah) |
Case-control | 29/29 | 30.93±8.94 25.42±4.98 |
24-36 38-41 |
PRT | 81.29±15.89 92.77±12.87 |
Serum | µg/l | AAS |
| (Atarod et al., 2015) | Eng | 2015 | Mazandaran (Sari) | Case-control | 43/43 | 20-40 20-40 |
12-14 | 77.9±16 97.3±11.2 |
Serum | µg/l | GF-AAS | |
| (Nazemi et al., 2015) | Eng | 2015 | Tehran (Tehran) | Case-control | 91/86 | 28.41±6.32 28.7±5.44 |
28.82±13.66 38.12±0.91 |
LBW | 80.69±28 78.48±25.54 |
Serum | µg/l | NR |
| (Jalili et al., 2015) | Per | 2015 | Razavi-Khorasan (Mashhad) | Cohort | 18/20 | 16-35 16-35 |
n/a | HLTH | 72.05±6.29 75.69±8.17 |
Serum | µg/l | AAS |
| (Mazloomi et al., 2021) | Eng | 2020 | Hamadan (Hamadan) | Case-control | 30/30 | 31(24-38) 31(24-38) |
> 20 | PE | 80.15±23.16 110.18±46.7 |
Serum | µg/l | AAS |
| (Moshfeghy et al., 2020) | Eng | 2020 | Fars (Shiraz) | Case-control | 25/50 | 25.76±3.65 25.66±3.52 |
First trimester | GDM | 50.6±10.88 66.02±10.57 |
Serum | µg/l | HG-AAS |
| Dietary Se | ||||||||||||
| Kooshki et al.(Kooshki et al., 2009) | Per | 2007 | North-Khorasan (Sabzevar) | Cross-sectional | 561 | 4.29±3.2 | General population | 124.7±4.9 | 3*24hr FR + FFQ | µg/d | FP | |
| (Kushki et al.) | Per | 2009 | North-Khorasan (Sabzevar) | Case-control | 100/100 | Total 26.7±6 |
>20 | HTN | 45.04±37.32 43.1±55.96 |
3*24hr FR | µg/d | FP |
| (Asemi et al., 2012) | Eng | 2012 | Isfahan (Kashan) | RCT | 37/37 | 25.7±3.1 24.2±3.3 |
28 | HLTH (both) |
110±40 110±30 |
3*24hr FR | µg/d | NUT IV |
| (Khoigani et al., 2012) | Eng | 2012 | Isfahan (Isfahan) | Cohort | 23/561 | 27.73±6.04 25.36±4.84 |
11-15 | PE | 50.41±33.4 43.44±34.17 |
48hr DR | µg/d | NUT IV |
| (Kazemian et al., 2013) | Per | 2013 | Tehran (Tehran) | Case-control | 200/263 | 29.27±5.96 27.4±4.8 |
33.39±4.67 33.22±3.73 |
HTN | 58.76±23.96 61.64±21.35 |
FFQ | µg/d | NUT III |
| (Aalami-Harandi et al., 2015) | Eng | 2014 | Isfahan (Kashan) | RCT | 37/37 | 24.2±3.3 25.7±3.1 |
27 | HLTH (at risk of PE) | 117.8±4.6 111±3.5 |
3*24hr FR | µg/d | NUT IV |
| (Monafi et al., 2003) | Per | 2014 | West-Azerbaijan (Urmia) | Cross-sectional | 118 | 12-16 | HLTH | 42.8±0 | 3*24hr FR | µg/d | FP II | |
| (Sheykhi et al., 2015) | Eng | 2015 | Isfahan (Isfahan) | Cross-sectional | 55 | Total 29.3±5.5 |
34.1±2.7 | PE | 81.5±40.7 | FFQ | µg/d | NUT IV |
| (Asemi et al., 2015) | Eng | 2015 | Markazi (Arak) | RCT | 35/35 | 27.6±5.3 29.6±3.6 |
24-28 | GDM (both) |
114.9±45.5 114.9±35.1 |
3*24hr DR | µg/d | NUT IV |
| (Parast and Paknahad, 2017) | Eng | 2017 | Isfahan (Isfahan) | Case-control | 40/40 | 29.4±4.9 28.9±5.2 |
26±1.5 26.1±1.5 |
GDM | 81±26 95±36 |
FFQ | µg/d | NUT IV |
| (Daneshzad et al., 2020) | Eng | 2020 | Isfahan (Isfahan) | Case-control | 35/35 | 27.6±5.3 29.6±3.6 |
25-28 | GDM | 60±2 70±2 |
3*24hr DR | µg/d | NUT IV |
| Umbilical cord Se | ||||||||||||
| (Mostafa-Gharehbaghi et al., 2012) | Eng | 2011 | East-Azerbaijan (Tabriz) | Longitudinal | 8/11 | 32 >= | BPD | 42.7±17.0 31.9±13.9 |
Serum | µg/l | HG-AAS | |
| (Boskabadi et al., 2012) | Eng | 2012 | Razavi-Khorasan (Mashhad) | RCT | (End-point in placebo group) 34 |
39 | HLTH | 106.3±18.2 101.9±15.9 |
Serum | µg/l | ET-AAS | |
| (Mohammadzadeh et al., 2012) | Eng | 2012 | Razavi-Khorasan (Mashhad) | Cross-sectional | 27/123 | 37 >= | RDS | 96.5±20.1 96.6±18.7 |
Serum | µg/l | ET-AAS+GF tubes | |
| (Peirovifar et al., 2013) | Eng | 2013 | East-Azerbaijan (Tabriz) | Longitudinal | 25/29 | 27.95±6.02 27.85±6.28 |
20>= | BPD | 69.82±28.47 60.11±24.59 |
Serum | µg/l | ET-AAS |
| (Alipour et al., 2015) | Per | 2014 | Kermanshah (Kermanshah) | Case-control | 29/29 | 30.93±8.94 25.42±4.98 |
24-36 38-41 |
PRT | 56.98±13.13 70.11±11.6 |
Serum | µg/l | AAS |
| (Nazemi et al., 2015) | Eng | 2015 | Tehran (Tehran) | Case-control | 91/86 | 28.41±6.32 28.7±5.44 |
28.82 38.12 |
LBW | 77.32±26.12 73.89±24.37 |
Serum | µg/l | n/a |
| AAS: Atomic absorption spectrometry, GF: Graphite furnace, HG: Hybrid generation, ET: Electro-thermal, FP: Food processor, NUT: Nutritionist, Se: Selenium, Per: Persian, Eng: English, RCT: Randomized clinical trial, PRT: Preterm birth, GDM: Gestational diabetes mellitus, PE: Pre-eclampsia, HLTH: Healthy, LBW: Low birth weight, MSCRG: Miscarriage, HTN: Hypertension, BPD: Bronchopulmonary dysplasia, RDS: Respiratory distress syndrome, n/a: not applicable, Note: For trial studies, baseline Se levels are reported.Values are as mean ± SD | ||||||||||||
| Table 2. Subgroups analysis results. | ||||||
| Subgroups | Effect sizes | Mean | 95% CI | Heterogeneity test | ||
| I2 (%) | P-value | |||||
| Maternal serum Se concentration (μg/l) | ||||||
| Total | 30 | 90.09 | 81.89, 98.29 | 98.8 | < 0.0001 | |
| Age (y) | ||||||
| <26 | 11 | 96.68 | 78.30, 115.05 | 99.4 | < 0.0001 | |
| >26 | 15 | 87.81 | 77.44, 98.17 | 97.6 | < 0.0001 | |
| Not specified | 4 | 80.74 | 68.73, 92.75 | 97.8 | < 0.0001 | |
| Body mass index (kg/m2) | ||||||
| <26 | 5 | 93.83 | 74.29, 113.36 | 98.5 | < 0.0001 | |
| >26 | 7 | 108.19 | 83.88, 132.49 | 98.8 | < 0.0001 | |
| Not specified | 18 | 82.11 | 72.29, 91.93 | 98.8 | < 0.0001 | |
| Health condition | ||||||
| Healthy | 17 | 95.75 | 85.72, 105.79 | 98.7 | < 0.0001 | |
| Gestational diabetes mellitus | 3 | 75.61 | 36.80, 114.42 | 99.4 | < 0.0001 | |
| Pre-eclampsia | 5 | 78.57 | 59.55, 97.60 | 98.0 | < 0.0001 | |
| Abortion | 2 | 86.89 | 67.83, 105.95 | 89.0 | 0.003 | |
| Low birth weight or preterm | 3 | 93.59 | 68.85, 118.34 | 98.2 | < 0.0001 | |
| Trimesters | ||||||
| First | 4 | 90.42 | 57.54, 123.29 | 99.5 | < 0.0001 | |
| Second | 2 | 87.68 | 68.67, 106.69 | 97.6 | < 0.0001 | |
| Third | 20 | 91.20 | 80.07, 102.33 | 98.8 | < 0.0001 | |
| Not specified | 4 | 83.73 | 74.67, 92.78 | 90.8 | < 0.0001 | |
| Province | ||||||
| Razavi Khorasan | 10 | 113.99 | 96.67, 131.30 | 98.9 | < 0.0001 | |
| Fars | 6 | 61.97 | 51.38, 72.55 | 97.7 | < 0.0001 | |
| East-Azerbaijan | 2 | 55.12 | 48.50, 61.74 | 84.9 | 0.010 | |
| Tehran | 6 | 90.93 | 82.20, 99.65 | 89.0 | < 0.0001 | |
| Hamadan | 2 | 94.25 | 64.88, 123.63 | 90.0 | 0.002 | |
| Kermanshah | 2 | 87.16 | 75.91, 98.41 | 89.1 | 0.003 | |
| Mazandaran | 2 | 87.68 | 68.67, 106.69 | 97.6 | < 0.0001 | |
| Year | ||||||
| 2004-2012 | 14 | 106.68 | 89.17, 124.19 | 99.0 | < 0.0001 | |
| 2013-2020 | 16 | 75.66 | 67.98, 83.34 | 98.0 | < 0.0001 | |
| Language | ||||||
| English | 22 | 88.72 | 78.20, 99.25 | 99.0 | < 0.0001 | |
| Persian | 8 | 93.64 | 83.01, 104.28 | 96.5 | < 0.0001 | |
| Study design | ||||||
| Randomized clinical trial | 2 | 122.68 | 118.31, 127.04 | 0.0 | 0.929 | |
| Case-control and cross-sectional | 26 | 88.84 | 79.93, 97.76 | 98.7 | < 0.0001 | |
| Cohort | 2 | 73.71 | 70.16, 77.27 | 58.2 | 0.122 | |
| Maternal serum Se concentration at delivery (μg/l) | ||||||
| Total | 4 | 94.73 | 72.78, 116.67 | 98.3 | < 0.0001 | |
| Health condition | ||||||
| Healthy | 2 | 98.62 | 62.60, 134.65 | 98.7 | < 0.0001 | |
| Pre-eclampcia | 1 | 71.22 | 65.83, 76.61 | |||
| Preterm | 1 | 110.56 | 104.30, 116.82 | |||
| Dietary Se intake (μg/d) | ||||||
| Total | 23 | 75.08 | 63.04, 87.13 | 100 | < 0.0001 | |
| Health condition | ||||||
| Healthy | 12 | 73.91 | 56.65, 91.16 | 99.9 | < 0.0001 | |
| Gestational diabetes mellitus | 4 | 94.36 | 72.81, 115.92 | 97.0 | < 0.0001 | |
| Hypertension | 2 | 53.64 | 37.38, 69.89 | 93.5 | < 0.0001 | |
| Pre-eclampcia | 4 | 57.09 | 37.55, 76.62 | 89.9 | < 0.0001 | |
| Not specified | 1 | 124.70 | 124.29, 125.11 | |||
| Trimesters | ||||||
| First | 1 | 124.70 | 124.29, 125.11 | |||
| Second | 3 | 43.41 | 41.16, 45.66 | 0.0 | 0.575 | |
| Third | 19 | 76.61 | 70.60, 82.62 | 99.8 | < 0.0001 | |
| Province | ||||||
| Isfahan | 15 | 74.90 | 68.10, 81.69 | 99.9 | < 0.0001 | |
| Tehran | 2 | 60.16 | 57.34, 62.98 | 5.2 | 0.304 | |
| West-Azerbaijan | 1 | 42.80 | 38.95, 46.65 | |||
| North-Khorasan | 3 | 71.07 | 6.83, 135.32 | 99.7 | < 0.0001 | |
| Markazi | 2 | 114.90 | 105.69, 124.11 | 0.0 | 1.000 | |
| Umbilical cord Se concentration (μg/l) | ||||||
| Total | 11 | 70.98 | 58.95, 83.02 | 97.9 | < 0.0001 | |
| Health condition | ||||||
| Healthy | 6 | 72.66 | 55.44, 89.89 | 98.5 | < 0.0001 | |
| Unhealthy | 5 | 68.93 | 52.67, 85.20 | 96.1 | < 0.0001 | |
| Table 3. The quality assessment of the included studies. | |||||||
| Study | Selection of participants | Confounding variables | Measurement of exposure | Blinding of outcome assessments | Incomplete outcome data | Selective outcome reporting | Total scorea |
| Noormohammadi et al. 2004 | L | U | L | L | L | L | 5 |
| Kooshki et al. 2007 | L | H | L | L | L | L | 5 |
| Iranpour et al. 2009 | L | U | L | L | L | L | 5 |
| Mohammadzadeh et al. 2009 | L | L | L | L | L | L | 6 |
| Mortazavi et al. 2009 | L | L | L | L | L | L | 6 |
| Tara et al. 2010 | U | U | L | U | L | L | 3 |
| Davaryari et al. 2011 | L | U | L | L | L | L | 5 |
| Gharehbaghi et al. 2011 | L | H | L | L | L | L | 5 |
| Maleki et al. 2011 | L | L | L | L | L | L | 6 |
| Akhlaghi et al. 2012 | L | U | L | L | L | L | 5 |
| Asemi et al. 2012 | U | U | H | H | L | L | 4 |
| Boskabadi et al. 2012 | U | L | L | U | H | L | 3 |
| Farzin and sajadi 2012 | L | U | L | L | L | L | 5 |
| Khoigani et al. 2012 | L | L | L | L | H | L | 5 |
| Mohammadzadeh et al. 2012 | L | L | L | L | L | L | 6 |
| Ghaemi and Foroohari 2013 | L | L | L | L | L | L | 6 |
| Kazemian et al. 2013 | L | L | L | L | L | L | 6 |
| Peirovifar et al. 2013 | L | L | L | L | L | L | 6 |
| Harandi et al. 2014 | L | U | L | L | L | L | 5 |
| Monafi et al. 2014 | L | H | L | L | L | L | 5 |
| Asemi et al. 2015 | L | U | L | L | L | L | 5 |
| Atarod et al. 2015 | L | U | L | L | L | L | 5 |
| Jalili et al. 2015 | L | H | L | L | H | L | 4 |
| Sheykhi et al. 2015 | L | H | L | L | L | L | 5 |
| Nazemi et al. 2015 | L | L | L | L | L | L | 6 |
| Mohammad parast et al. 2017 | L | L | L | L | L | L | 6 |
| Arabpour et al. 2018 | U | U | U | L | U | L | 2 |
| Daneshzad et al. 2020 | L | L | L | L | L | L | 6 |
| Mazloomi et al. 2020 | L | L | L | L | L | L | 6 |
| Moshfeghy et al. 2020 | L; | L | L | L | L | L | 6 |
L: low risk, H: high risk, U: unclear risk; a overall score considered as number of low risk domains..png) .png) .png) |
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Discussion
To the best of the authors’ knowledge, this is the first meta-analysis of Se status conducted on Iranian pregnant women. The meta-analysis of 1245 Iranian pregnant women from 30 studies enabled the authors to assess reliable estimates of serum Se at the national level, and the results showed that the overall estimate of serum Se was 90.09 μg/l. The pooled result was close to the results reported in Korea and Spain (Choi et al., 2016), but it was higher than the results reported in Turkey (Kilinc et al., 2008), Iraq (Alawad et al., 2019), and Poland (Polanska et al., 2016), and lower than that results reported in the United States (Hawkes et al., 2004), and probably Japan (Nakayama et al., 2019) (third trimester was considered).
Stratified analysis based on the provincial distribution of Se (Figure 2), Fars, East-Azerbaijan, West-Azerbaijan, and likely Kerman (unpublished), may require more attention by monitoring Se status during pregnancy.
Different serum Se levels in pregnant women have been reported in various countries and could be due to different soil Se, dietary habits, and lifestyle (Stoffaneller and Morse, 2015, Wang et al., 2020), as well as differences in other environmental exposure in the population of each country (Tan et al., 2018). It is noteworthy that the Se status could be compensated in some Se deficient countries by improving policies.
Finland and New Zealand are two countries with experience of Se deficiency in the 1980s. Finland has experienced Se deficiency, which was mainly attributed to low soil Se. Finnish government mandated Se improvement strategies by Se-rich fertilizers for cereal and grassland crops which resulted in a notable improvement in Se status in the Finnish population. The New Zealand government implemented the same in recent years, by enhancing Se concentration in livestock by promoting animal feed Se supplementation in deficient regions and importing wheat from Se-rich countries such as the USA and Australia. Decreased incidence of PE in these two countries has been attributed to the improvement of Se status (Vanderlelie and Perkins, 2011).
Moreover, interventional studies have demonstrated potential benefits of Se supplementation during pregnancy, such as reducing the incidence of PE (Tara et al., 2010a), improving glucose homeostasis (Asemi et al., 2015) and oxidative stress (Asemi et al., 2015, Tara et al., 2010b), and reducing the effect on pulsatility index (an indicator of intrauterine growth restriction) (Mesdaghinia et al., 2017). On the other hand, results from observational studies are still contradictory (Farzin and Sajadi, 2012, Liu et al., 2021, Mohammadzadeh et al., 2009, Solé-Navais et al., 2021).
Stratified analysis by maternal age showed that the mean values for <26-year-old women were 96.68 μg/l (95% CI: 78.30, 115.05 μg/l) and for >26-year-old subgroup were 87.81 μg/l (95% CI: 77.44, 98.17 μg/l). Also, mean values for maternal BMI <26 and >26 subgroups were 93.83μg/l (95% CI: 74.29, 113.36 μg/l) and 108.19μg/l (95% CI: 83.88, 132.49 μg/l), respectively. Subgroup analysis based on years of publication showed that studies published in 2004-2012 including 14 effect sizes had a mean value of 106.68 μg/l (95% CI: 89.17, 124.19 μg/l) and studies published in 2013-2020 including 16 effect sizes had the mean value of 75.66μg/l (95% CI: 67.98, 83.34 μg/l). The decreasing trend in serum Se can be associated with an increasing prevalence of PE among pregnant women in Iran (Kharaghani et al., 2016, Vanderlelie and Perkins, 2011).
According to the result of the meta-analysis, the overall estimate of dietary Se intake revealed 75.08 μg/d by pooling 23 effect sizes from 5 provinces. Of the eleven studies, 6 of them were conducted in Isfahan (54%), 2 in North-Khorasan (18%), and only one study (9%) was conducted in three provinces (Tehran, West-Azerbaijan, Markazi). Data of Isfahan can be divided into two cities, Kashan with dietary Se intake of 113.12 μg/d (95% CI: 105.69, 124.11 μg/d) and Isfahan with 60.50 μg/d (CI: 55.48, 65.51), which can be interpreted as within provincial variation in Se intake.
Considerable differences in dietary Se intake between studies could be due to different measurement methods (NUT4, FP), or year of study; moreover, seasonal variation (Ma et al., 2006) and anthropometric indices (Nazemi et al., 2012, Zhong et al., 2018) may affect dietary Se intake. Also, in a study by Jalili et al., a positive relationship between physical activity and serum Se was reported (Jalili et al., 2015).
Signs of Se inadequacy have been seen in different parts of Iran. A study by Hashemipour et al. showed a probable Se deficiency in schoolchildren of Semirom (Isfahan) (Hashemipour et al., 2008). In a study conducted in Marvdasht (Fars), Se deficiency was considered an effective factor in goiter prevalence (Dabbaghmanesh et al., 2007). Furthermore, in the south-east of Iran (Zahedan), 22.9% and 29.1% of male and female Thalassemia adolescent patients were diagnosed as Se deficient (Mashhadi et al., 2014). Rafraf et al. reported that 53.33% of women of childbearing age in Tabriz (East-Azerbaijan), were Se deficient (<80 μg/l) (Rafraf et al., 2008). These reports, in addition to the provincial Se status, emphasize that more studies on Se status are needed in regions suspected of Se inadequacy such as East and West-Azerbaijan, Isfahan and Fars, and South-East provinces of the country.
The present study represents the first comprehensive meta-analysis examining the Se status in Iranian pregnant women. However, several limitations should be considered in the interpretation of the results. First, the sample size in some of the included studies was not sufficiently large. Second, significant heterogeneity between studies resulted from variation in a year, city, maternal age, and maybe measurement method. A well-designed national assessment is needed to have a reliable evaluation on Se status among pregnant women.
Conclusions
The present study shows that the overall serum and intake of Se in Iranian pregnant women is acceptable. Some parts of the country need monitoring to prevent Se inadequacy and related-adverse complications in pregnancy and conception.
Conflict of interest
The authors declare that they have no conflict of interest.
Authors' contributions
Daneshvar M, Hasanzadeh M, and Djafarian K contributed to the study concept and design; Daneshvar M, Yadegari A, and Djafarian K designed the search strategy and screened papers; Daneshvar M performed statistical analysis; Daneshvar M, Yadegari A, and Hasanzadeh M wrote the manuscript. Finally, all authors approved the manuscript for publishing.
References
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Akhlaghi F, Bagheri SM & Rajabi O 2012. A comparative study of relationship between micronutrients and gestational diabetes. International scholarly research notices. 2012.
Al-Othman AM, et al. 2012. Daily intake of selenium and concentrations in blood of residents of Riyadh City, Saudi Arabia. Environmental geochemistry and health. 34 (4): 417-431.
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Asemi Z, Jamilian M, Mesdaghinia E & Esmaillzadeh A 2015. Effects of selenium supplementation on glucose homeostasis, inflammation, and oxidative stress in gestational diabetes: Randomized, double-blind, placebo-controlled trial. Nutrition. 31 (10): 1235-1242.
Asemi Z, et al. 2012. Effect of daily consumption of probiotic yogurt on oxidative stress in pregnant women: a randomized controlled clinical trial. Annals of nutrition and metabolism. 60 (1): 62-68.
Atarod Z, Emadi N, Saeedi Saravi SS, Modanlookordi M & Shokrzadeh M 2015. Copper and selenium levels in women with second-trimester induced abortion in Mazandaran, 2009: A case control study. Pharmaceutical and biomedical research. 1 (1): 44-47.
Boskabadi H, et al. 2012. Effect of prenatal selenium supplementation on cord blood selenium and lipid profile. Pediatrics & neonatology. 53 (6): 334-339.
Choi R, et al. 2016. A prospective study of serum trace elements in healthy Korean pregnant women. Nutrients. 8 (11): 749.
Chun OK, et al. 2010. Estimation of antioxidant intakes from diet and supplements in US adults. Journal of nutrition. 140 (2): 317-324.
Dabbaghmanesh MH, Sadegholvaad A, Ejtehadi F & Omrani G 2007. Low serum selenium concentration as a possible factor for persistent goiter in Iranian school children. Biofactors. 29 (2, 3): 77-82.
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Duffield AJ, Thomson CD, Hill KE & Williams S 1999. An estimation of selenium requirements for New Zealanders. American journal of clinical nutrition. 70 (5): 896-903.
Farzin L & Sajadi F 2012. Comparison of serum trace element levels in patients with or without pre-eclampsia. Journal of research in medical sciences. 17 (10): 938.
Filippini T, et al. 2017. Toenail selenium as an indicator of environmental exposure: A cross-sectional study. Molecular medicine reports. 15 (5): 3405-3412.
Ghaemi SZ, et al. 2013. A prospective study of selenium concentration and risk of preeclampsia in pregnant Iranian women: a nested case–control study. Biological trace element research. 152 (2): 174-179.
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To the best of the authors’ knowledge, this is the first meta-analysis of Se status conducted on Iranian pregnant women. The meta-analysis of 1245 Iranian pregnant women from 30 studies enabled the authors to assess reliable estimates of serum Se at the national level, and the results showed that the overall estimate of serum Se was 90.09 μg/l. The pooled result was close to the results reported in Korea and Spain (Choi et al., 2016), but it was higher than the results reported in Turkey (Kilinc et al., 2008), Iraq (Alawad et al., 2019), and Poland (Polanska et al., 2016), and lower than that results reported in the United States (Hawkes et al., 2004), and probably Japan (Nakayama et al., 2019) (third trimester was considered).
Stratified analysis based on the provincial distribution of Se (Figure 2), Fars, East-Azerbaijan, West-Azerbaijan, and likely Kerman (unpublished), may require more attention by monitoring Se status during pregnancy.
Different serum Se levels in pregnant women have been reported in various countries and could be due to different soil Se, dietary habits, and lifestyle (Stoffaneller and Morse, 2015, Wang et al., 2020), as well as differences in other environmental exposure in the population of each country (Tan et al., 2018). It is noteworthy that the Se status could be compensated in some Se deficient countries by improving policies.
Finland and New Zealand are two countries with experience of Se deficiency in the 1980s. Finland has experienced Se deficiency, which was mainly attributed to low soil Se. Finnish government mandated Se improvement strategies by Se-rich fertilizers for cereal and grassland crops which resulted in a notable improvement in Se status in the Finnish population. The New Zealand government implemented the same in recent years, by enhancing Se concentration in livestock by promoting animal feed Se supplementation in deficient regions and importing wheat from Se-rich countries such as the USA and Australia. Decreased incidence of PE in these two countries has been attributed to the improvement of Se status (Vanderlelie and Perkins, 2011).
Moreover, interventional studies have demonstrated potential benefits of Se supplementation during pregnancy, such as reducing the incidence of PE (Tara et al., 2010a), improving glucose homeostasis (Asemi et al., 2015) and oxidative stress (Asemi et al., 2015, Tara et al., 2010b), and reducing the effect on pulsatility index (an indicator of intrauterine growth restriction) (Mesdaghinia et al., 2017). On the other hand, results from observational studies are still contradictory (Farzin and Sajadi, 2012, Liu et al., 2021, Mohammadzadeh et al., 2009, Solé-Navais et al., 2021).
Stratified analysis by maternal age showed that the mean values for <26-year-old women were 96.68 μg/l (95% CI: 78.30, 115.05 μg/l) and for >26-year-old subgroup were 87.81 μg/l (95% CI: 77.44, 98.17 μg/l). Also, mean values for maternal BMI <26 and >26 subgroups were 93.83μg/l (95% CI: 74.29, 113.36 μg/l) and 108.19μg/l (95% CI: 83.88, 132.49 μg/l), respectively. Subgroup analysis based on years of publication showed that studies published in 2004-2012 including 14 effect sizes had a mean value of 106.68 μg/l (95% CI: 89.17, 124.19 μg/l) and studies published in 2013-2020 including 16 effect sizes had the mean value of 75.66μg/l (95% CI: 67.98, 83.34 μg/l). The decreasing trend in serum Se can be associated with an increasing prevalence of PE among pregnant women in Iran (Kharaghani et al., 2016, Vanderlelie and Perkins, 2011).
According to the result of the meta-analysis, the overall estimate of dietary Se intake revealed 75.08 μg/d by pooling 23 effect sizes from 5 provinces. Of the eleven studies, 6 of them were conducted in Isfahan (54%), 2 in North-Khorasan (18%), and only one study (9%) was conducted in three provinces (Tehran, West-Azerbaijan, Markazi). Data of Isfahan can be divided into two cities, Kashan with dietary Se intake of 113.12 μg/d (95% CI: 105.69, 124.11 μg/d) and Isfahan with 60.50 μg/d (CI: 55.48, 65.51), which can be interpreted as within provincial variation in Se intake.
Considerable differences in dietary Se intake between studies could be due to different measurement methods (NUT4, FP), or year of study; moreover, seasonal variation (Ma et al., 2006) and anthropometric indices (Nazemi et al., 2012, Zhong et al., 2018) may affect dietary Se intake. Also, in a study by Jalili et al., a positive relationship between physical activity and serum Se was reported (Jalili et al., 2015).
Signs of Se inadequacy have been seen in different parts of Iran. A study by Hashemipour et al. showed a probable Se deficiency in schoolchildren of Semirom (Isfahan) (Hashemipour et al., 2008). In a study conducted in Marvdasht (Fars), Se deficiency was considered an effective factor in goiter prevalence (Dabbaghmanesh et al., 2007). Furthermore, in the south-east of Iran (Zahedan), 22.9% and 29.1% of male and female Thalassemia adolescent patients were diagnosed as Se deficient (Mashhadi et al., 2014). Rafraf et al. reported that 53.33% of women of childbearing age in Tabriz (East-Azerbaijan), were Se deficient (<80 μg/l) (Rafraf et al., 2008). These reports, in addition to the provincial Se status, emphasize that more studies on Se status are needed in regions suspected of Se inadequacy such as East and West-Azerbaijan, Isfahan and Fars, and South-East provinces of the country.
The present study represents the first comprehensive meta-analysis examining the Se status in Iranian pregnant women. However, several limitations should be considered in the interpretation of the results. First, the sample size in some of the included studies was not sufficiently large. Second, significant heterogeneity between studies resulted from variation in a year, city, maternal age, and maybe measurement method. A well-designed national assessment is needed to have a reliable evaluation on Se status among pregnant women.
Conclusions
The present study shows that the overall serum and intake of Se in Iranian pregnant women is acceptable. Some parts of the country need monitoring to prevent Se inadequacy and related-adverse complications in pregnancy and conception.
Conflict of interest
The authors declare that they have no conflict of interest.
Authors' contributions
Daneshvar M, Hasanzadeh M, and Djafarian K contributed to the study concept and design; Daneshvar M, Yadegari A, and Djafarian K designed the search strategy and screened papers; Daneshvar M performed statistical analysis; Daneshvar M, Yadegari A, and Hasanzadeh M wrote the manuscript. Finally, all authors approved the manuscript for publishing.
References
Aalami-Harandi R, Karamali M & Asemi Z 2015. The favorable effects of garlic intake on metabolic profiles, hs-CRP, biomarkers of oxidative stress and pregnancy outcomes in pregnant women at risk for pre-eclampsia: randomized, double-blind, placebo-controlled trial. Journal of maternal-fetal & neonatal medicine. 28 (17): 2020-2027.
Akhlaghi F, Bagheri SM & Rajabi O 2012. A comparative study of relationship between micronutrients and gestational diabetes. International scholarly research notices. 2012.
Al-Othman AM, et al. 2012. Daily intake of selenium and concentrations in blood of residents of Riyadh City, Saudi Arabia. Environmental geochemistry and health. 34 (4): 417-431.
Alawad AS, Alawadi SB, Al-Dujaily IH & Alawadi NB 2019. Trace Elements in Pregnant Women from Babil Province, Iraq. Annals of tropical medicine and health. 22: 64-71.
Alipour AA, Babaei H, Hemmati M, Rezaei M & Hoseininezhad Z 2015. Comparison of maternal and umbilical cord blood selenium levels in preterm and term neonates. Journal of Kermanshah University of medical sciences. 18 (9): 509-515.
Asemi Z, Jamilian M, Mesdaghinia E & Esmaillzadeh A 2015. Effects of selenium supplementation on glucose homeostasis, inflammation, and oxidative stress in gestational diabetes: Randomized, double-blind, placebo-controlled trial. Nutrition. 31 (10): 1235-1242.
Asemi Z, et al. 2012. Effect of daily consumption of probiotic yogurt on oxidative stress in pregnant women: a randomized controlled clinical trial. Annals of nutrition and metabolism. 60 (1): 62-68.
Atarod Z, Emadi N, Saeedi Saravi SS, Modanlookordi M & Shokrzadeh M 2015. Copper and selenium levels in women with second-trimester induced abortion in Mazandaran, 2009: A case control study. Pharmaceutical and biomedical research. 1 (1): 44-47.
Boskabadi H, et al. 2012. Effect of prenatal selenium supplementation on cord blood selenium and lipid profile. Pediatrics & neonatology. 53 (6): 334-339.
Choi R, et al. 2016. A prospective study of serum trace elements in healthy Korean pregnant women. Nutrients. 8 (11): 749.
Chun OK, et al. 2010. Estimation of antioxidant intakes from diet and supplements in US adults. Journal of nutrition. 140 (2): 317-324.
Dabbaghmanesh MH, Sadegholvaad A, Ejtehadi F & Omrani G 2007. Low serum selenium concentration as a possible factor for persistent goiter in Iranian school children. Biofactors. 29 (2, 3): 77-82.
Daneshzad E, Tehrani H, Bellissimo N & Azadbakht L 2020. Dietary Total Antioxidant Capacity and Gestational Diabetes Mellitus: A Case-Control Study. Oxidative medicine and cellular longevity. 2020.
Davaryari N, Ramin Razavi Panah SHM, Homa Oskouiyan,, Marzieh Mohajeri, Nayereh Ghomian & Ghasemi SM 2011. A Comparison of Serum Level of Selenium in Women with Preeclampsia and Normal Pregnant Women. Medical journal of Mashhad University of medical sciences. 54 (2): 80-85.
Duffield AJ, Thomson CD, Hill KE & Williams S 1999. An estimation of selenium requirements for New Zealanders. American journal of clinical nutrition. 70 (5): 896-903.
Farzin L & Sajadi F 2012. Comparison of serum trace element levels in patients with or without pre-eclampsia. Journal of research in medical sciences. 17 (10): 938.
Filippini T, et al. 2017. Toenail selenium as an indicator of environmental exposure: A cross-sectional study. Molecular medicine reports. 15 (5): 3405-3412.
Ghaemi SZ, et al. 2013. A prospective study of selenium concentration and risk of preeclampsia in pregnant Iranian women: a nested case–control study. Biological trace element research. 152 (2): 174-179.
Hashemipour M, et al. 2008. Goiter persistence after iodine replenishment, the potential role of selenium deficiency in goitrous schoolchildren of Semirom, Iran. Experimental and clinical endocrinology & diabetes. 116 (02): 75-79.
Hawkes WC, Alkan Z, Lang K & King JC 2004. Plasma selenium decrease during pregnancy is associated with glucose intolerance. Biological trace element research. 100 (1): 19-29.
Higgins J & Deeks J 2011. Obtaining standard deviations from standard errors and confidence intervals for group means, Cochrane handbook for systematic reviews of interventions.
Higgins J & Green S 2019. 16.1. 3.1 Imputing standard deviations. Cochrane Handb. Syst. Rev. Interv. https://handb ook-5-1. coch r ane. org/chapt er_16/16_1_3_1impu ting_stand ard_devia tions. htm. Accessed 2
Higgins JP, et al. 2011. The Cochrane Collaboration’s tool for assessing risk of bias in randomised trials. British medical journal. 343.
Higgins JP & Thompson SG 2002. Quantifying heterogeneity in a meta-analysis. Statistics in medicine. 21 (11): 1539-1558.
Hubalewska-Dydejczyk A, Duntas L & Gilis-Januszewska A 2020. Pregnancy, thyroid, and the potential use of selenium. Hormones. 19 (1): 47-53.
Ibrahim SA, Kerkadi A & Agouni A 2019. Selenium and health: An update on the situation in the Middle East and North Africa. Nutrients. 11 (7): 1457.
Iranpour R, et al. 2009. Comparison of maternal and umbilical cord blood selenium levels in term and preterm infants. Chinese journal of contemporary pediatrics. 11 (7): 513-516.
Jalili A, Akhlaghi F, Bagheri SM, Chehelmard ElahAbadi P & Khadem Rezaiyan M 2015. Relationship between micronutrients of active and inactive mothers with Neonatal growth. Iranian journal of obstetrics, gynecology and infertility. 18 (145): 8-13.
Johnson CC, Fordyce FM & Rayman MP 2010. Symposium on ‘Geographical and geological influences on nutrition’Factors controlling the distribution of selenium in the environment and their impact on health and nutrition: Conference on ‘Over-and undernutrition: challenges and approaches’. Proceedings of the nutrition society. 69 (1): 119-132.
Kazemian E, Dorosti- Motlagh AR, Sotoudeh G, Eshraghian MR & Ansary S 2013. Nutritional Status of Women with Gestational Hypertension Compared to Normal Pregnant Women. Journal of Rafsanjan University of medical sciences. 12 (10): 793-806.
Kharaghani R, Cheraghi Z, Esfahani BO, Mohammadian Z & Nooreldinc RS 2016. Prevalence of preeclampsia and eclampsia
in Iran. Archives of Iranian medicine.19 (1): 0-0.
Khoigani MG, Paknahad Z & Mardanian F 2012. The relationship between nutrients intake and preeclampsia in pregnant women. Journal of research in medical sciences.(2): S210-S217.
Kieliszek M 2019. Selenium–fascinating microelement, properties and sources in food. Molecules. 24 (7): 1298.
Kilinc M, Guven MA, Ezer M, Ertas IE & Coskun A 2008. Evaluation of serum selenium levels in Turkish women with gestational diabetes mellitus, glucose intolerants, and normal controls. Biological trace element research. 123 (1): 35-40.
Kim SY, et al. 2013. Testing a tool for assessing the risk of bias for nonrandomized studies showed moderate reliability and promising validity. Journal of clinical epidemiology. 66 (4): 408-414.
Kipp AP, et al. 2015. Revised reference values for selenium intake. Journal of trace elements in medicine and biology. 32: 195-199.
Kooshki A, Yaghoubi MA & Rahnama Rahsepar F 2009. Comparison of Energy and Nutrient Intakes in Pregnant Women in Sabzevar with Dietary Reference Intakes. Iranian journal of obstetrics, gynecology and infertility. 12 (1): 49-53.
Koukkou E, et al. 2014. Urine selenium changes during pregnancy do not correlate with thyroid autoantibodies in a mildly iodine deficient population. Biological trace element research. 157 (1): 9-13.
Kushki A, Forough S & Akbari A The relationship between diet and gestational hypertension. Journal of Sazevar medical university. 16 (2): 10-107 [Persian].
Kyozuka H, et al. 2021. Effect of Preconception Selenium Intake on the Risk for Gestational Diabetes: The Japan Environment and Children’s Study. Antioxidants. 10 (4): 568.
Lin L & Chu H 2018. Quantifying publication bias in meta-analysis. Biometrics. 74 (3): 785-794.
Liu PJ, et al. 2021. Associations of serum selenium levels in the first trimester of pregnancy with the risk of gestational diabetes mellitus and preterm birth: a preliminary cohort study. Biological trace element research. 199: 527-534.
Ma Y, et al. 2006. Seasonal variation in food intake, physical activity, and body weight in a predominantly overweight population. European journal of clinical nutrition. 60 (4): 519-528.
Maleki A, et al. 2011. The relationship between plasma level of Se and preeclampsia. Hypertension in pregnancy. 30 (2): 180-187.
Mariath AB, et al. 2011. The possible role of selenium status in adverse pregnancy outcomes. British journal of nutrition. 105 (10): 1418-1428.
Mashhadi MA, Heidari Z, Sepehri Z, Bakhshipour AR & Karimkoshte A 2014. The selenium status in thalassemia patients in South East of iran. International journal of hematology-oncology and stem cell research. 8 (4): 1.
Mazloomi S, Khodadadi I, Alimohammadi S & Shafiee G 2021. Correlation of thioredoxin reductase (TrxR) and nitric oxide synthase (NOS) activities with serum trace elements in preeclampsia. Clinical and experimental hypertension. 43 (2): 120-124.
Mesdaghinia E, Rahavi A, Bahmani F, Sharifi N & Asemi Z 2017. Clinical and metabolic response to selenium supplementation in pregnant women at risk for intrauterine growth restriction: randomized, double-blind, placebo-controlled trial. Biological trace element research. 178 (1): 14-21.
Mohammadzadeh A, et al. 2009. Maternal serum selenium and low birth weight neonates. Journal of neonatal-perinatal medicine. 2 (2): 103-107.
Mohammadzadeh A, et al. 2012. Selenium Level of Umbilical Cord Blood: Is it related to Respiratory Distress Syndrome? Iranian journal of nephrology. 1 (3): 24-28.
Monafi M, Rabiee Pour S & Pourheidar B 2003. Evaluation of food consumption in pregnant women referring to health centers in Urmia. Medical journal of Urmia University of medical sciences. 14 (4): 9-15.
Moshfeghy Z, et al. 2020. The predictive value of selenium in diagnosis of gestational diabetes: a nested case-control study. International journal of general medicine. 13: 53-60.
Mostafa-Gharehbaghi M, et al. 2012. Determination of selenium in serum samples of preterm newborn infants with bronchopulmonary dysplasia using a validated hydride generation system. Biological trace element research. 147 (1): 1-7.
Nakayama SF, et al. 2019. Blood mercury, lead, cadmium, manganese and selenium levels in pregnant women and their determinants: the Japan Environment and Children’s Study (JECS). Journal of exposure science
& environmental epidemiology. 29 (5):
633-647.
Nazemi L, et al. 2012. Selenium status in soil, water and essential crops of Iran. Iranian journal of environmental health science & engineering. 9 (1): 1-8.
Nazemi L, et al. 2015. Comparison of maternal and umbilical cord blood selenium levels in low and normal birth weight neonates. Journal of family & reproductive health. 9 (3): 125.
Noormohammadi Isa, Mehdizadeh Abolfazl, Mandegar Mansoureh & Meamarzadeh Ali Reza 2004. Association of serum zinc and selenium concentration in the etiology of miscarriage in Iranian women. Medical science journal. 14 (2): 89-92.
Okunade KS, et al. 2018. Selenium deficiency and pregnancy outcome in pregnant women with HIV in Lagos, Nigeria. International journal of gynecology & obstetrics. 142 (2): 207-213.
Parast VM & Paknahad Z 2017. Antioxidant status and risk of gestational diabetes mellitus: a case-control study. Clinical nutrition research. 6 (2): 81.
Peirovifar A, Gharehbaghi MM, Abdulmohammad-Zadeh H, Sadegi GH & Jouyban A 2013. Serum selenium levels of the very low birth weight premature newborn infants with bronchopulmonary dysplasia. Journal of trace elements in medicine and biology. 27 (4): 317-321.
Pieczyńska J & Grajeta H 2015. The role of selenium in human conception and pregnancy. Journal of trace elements in medicine and biology. 29: 31-38.
Polanska K, et al. 2016. Selenium status during pregnancy and child psychomotor development-Polish Mother and Child Cohort study. Pediatric research. 79 (6): 863-869.
Rafraf M, Mahdavi R & Rashidi MR 2008. Serum selenium levels in healthy women in Tabriz, Iran. Food and nutrition bulletin. 29 (2): 83-86.
Rayman MP 2000. The importance of selenium to human health. Lancet. 356 (9225): 233-241.
Rayman MP 2008. Food-chain selenium and human health: emphasis on intake. British journal of nutrition. 100 (2): 254-268.
Rayman MP 2012. Selenium and human health. Lancet. 379 (9822): 1256-1268.
Sheykhi M, Paknahad Z & Hasanzadeh A 2015. Dietary nutrient intake and antioxidant status in preeclamptic women. Advanced biomedical research. 4: 183.
Sieniawska CE, Meniskov R & Delves HT 1999. Determination of total selenium in serum, whole blood and erythrocytes by ICP-MS. Journal of analytical atomic spectrometry. 14 (2): 109-112.
Solé-Navais P, et al. 2021. Maternal Dietary Selenium Intake during Pregnancy Is Associated with Higher Birth Weight and Lower Risk of Small for Gestational Age Births in the Norwegian Mother, Father and Child Cohort Study. Nutrients. 13 (1): 23.
Stoffaneller R & Morse NL 2015. A review of dietary selenium intake and selenium status in Europe and the Middle East. Nutrients. 7 (3): 1494-1537.
Tan LC, Nancharaiah YV, van Hullebusch ED & Lens PN 2018. Selenium: environmental significance, pollution, and biological treatment technologies. Biotechnology advances. 34 (5): 886-907.
Tara F, et al. 2010a. Selenium supplementation and the incidence of preeclampsia in pregnant Iranian women: a randomized, double-blind, placebo-controlled pilot trial. Taiwanese journal of obstetrics and gynecology. 49 (2): 181-187.
Tara F, et al. 2010b. Prooxidant-antioxidant balance in pregnancy: a randomized double-blind placebo-controlled trial of selenium supplementation. Journal of perinatal medcine. 38 (5): 473-478.
Vanderlelie J & Perkins A 2011. Selenium and preeclampsia: a global perspective. Pregnancy Hypertension. International journal of women's cardiovascular health. 1 (3-4): 213-224.
Wang X, et al. 2020. Selenium Nutritional Status of Rural Residents and Its Correlation with Dietary Intake Patterns in a Typical Low-Selenium Area in China. Nutrients. 12 (12): 3816.
Xia Y, et al. 2010. Optimization of selenoprotein P and other plasma selenium biomarkers for the assessment of the selenium nutritional requirement: a placebo-controlled, double-blind study of selenomethionine supplementation in selenium-deficient Chinese subjects. American journal of clinical nutrition. 92 (3): 525-531.
Zachara BA 2018. Selenium in complicated pregnancy. a review. Advances in clinical chemistry. 86: 157-178.
Zhong Q, Lin R & Nong Q 2018. Adiposity and serum selenium in US adults. Nutrients. 10 (6): 727.
Type of article: review article |
Subject:
public specific
Received: 2021/08/28 | Published: 2023/05/20 | ePublished: 2023/05/20
Received: 2021/08/28 | Published: 2023/05/20 | ePublished: 2023/05/20
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25. Hubalewska-Dydejczyk A, Duntas L & Gilis-Januszewska A 2020. Pregnancy, thyroid, and the potential use of selenium. Hormones. 19 (1): 47-53.
26. Ibrahim SA, Kerkadi A & Agouni A 2019. Selenium and health: An update on the situation in the Middle East and North Africa. Nutrients. 11 (7): 1457.
27. Iranpour R, et al. 2009. Comparison of maternal and umbilical cord blood selenium levels in term and preterm infants. Chinese journal of contemporary pediatrics. 11 (7): 513-516.
28. Jalili A, Akhlaghi F, Bagheri SM, Chehelmard ElahAbadi P & Khadem Rezaiyan M 2015. Relationship between micronutrients of active and inactive mothers with Neonatal growth. Iranian journal of obstetrics, gynecology and infertility. 18 (145): 8-13.
29. Johnson CC, Fordyce FM & Rayman MP 2010. Symposium on ‘Geographical and geological influences on nutrition’Factors controlling the distribution of selenium in the environment and their impact on health and nutrition: Conference on ‘Over-and undernutrition: challenges and approaches’. Proceedings of the nutrition society. 69 (1): 119-132.
30. Kazemian E, Dorosti- Motlagh AR, Sotoudeh G, Eshraghian MR & Ansary S 2013. Nutritional Status of Women with Gestational Hypertension Compared to Normal Pregnant Women. Journal of Rafsanjan University of medical sciences. 12 (10): 793-806.
31. Kharaghani R, Cheraghi Z, Esfahani BO, Mohammadian Z & Nooreldinc RS 2016. Prevalence of preeclampsia and eclampsia in Iran. Archives of Iranian medicine. 19 (1): 0-0.
32. Khoigani MG, Paknahad Z & Mardanian F 2012. The relationship between nutrients intake and preeclampsia in pregnant women. Journal of research in medical sciences.(2): S210-S217.
33. Kieliszek M 2019. Selenium–fascinating microelement, properties and sources in food. Molecules. 24 (7): 1298.
34. Kilinc M, Guven MA, Ezer M, Ertas IE & Coskun A 2008. Evaluation of serum selenium levels in Turkish women with gestational diabetes mellitus, glucose intolerants, and normal controls. Biological trace element research. 123 (1): 35-40.
35. Kim SY, et al. 2013. Testing a tool for assessing the risk of bias for nonrandomized studies showed moderate reliability and promising validity. Journal of clinical epidemiology. 66 (4): 408-414.
36. Kipp AP, et al. 2015. Revised reference values for selenium intake. Journal of trace elements in medicine and biology. 32: 195-199.
37. Kooshki A, Yaghoubi MA & Rahnama Rahsepar F 2009. Comparison of Energy and Nutrient Intakes in Pregnant Women in Sabzevar with Dietary Reference Intakes. Iranian journal of obstetrics, gynecology and infertility. 12 (1): 49-53.
38. Koukkou E, et al. 2014. Urine selenium changes during pregnancy do not correlate with thyroid autoantibodies in a mildly iodine deficient population. Biological trace element research. 157 (1): 9-13.
39. Kushki A, Forough S & Akbari A The relationship between diet and gestational hypertension. Journal of Sazevar medical university. 16 (2): 10-107 [Persian].
40. Kyozuka H, et al. 2021. Effect of Preconception Selenium Intake on the Risk for Gestational Diabetes: The Japan Environment and Children’s Study. Antioxidants. 10 (4): 568.
41. Lin L & Chu H 2018. Quantifying publication bias in meta-analysis. Biometrics. 74 (3): 785-794.
42. Liu PJ, et al. 2021. Associations of serum selenium levels in the first trimester of pregnancy with the risk of gestational diabetes mellitus and preterm birth: a preliminary cohort study. Biological trace element research. 199: 527-534.
43. Ma Y, et al. 2006. Seasonal variation in food intake, physical activity, and body weight in a predominantly overweight population. European journal of clinical nutrition. 60 (4): 519-528.
44. Maleki A, et al. 2011. The relationship between plasma level of Se and preeclampsia. Hypertension in pregnancy. 30 (2): 180-187.
45. Mariath AB, et al. 2011. The possible role of selenium status in adverse pregnancy outcomes. British journal of nutrition. 105 (10): 1418-1428.
46. Mashhadi MA, Heidari Z, Sepehri Z, Bakhshipour AR & Karimkoshte A 2014. The selenium status in thalassemia patients in South East of iran. International journal of hematology-oncology and stem cell research. 8 (4): 1.
47. Mazloomi S, Khodadadi I, Alimohammadi S & Shafiee G 2021. Correlation of thioredoxin reductase (TrxR) and nitric oxide synthase (NOS) activities with serum trace elements in preeclampsia. Clinical and experimental hypertension. 43 (2): 120-124.
48. Mesdaghinia E, Rahavi A, Bahmani F, Sharifi N & Asemi Z 2017. Clinical and metabolic response to selenium supplementation in pregnant women at risk for intrauterine growth restriction: randomized, double-blind, placebo-controlled trial. Biological trace element research. 178 (1): 14-21.
49. Mohammadzadeh A, et al. 2009. Maternal serum selenium and low birth weight neonates. Journal of neonatal-perinatal medicine. 2 (2): 103-107.
50. Mohammadzadeh A, et al. 2012. Selenium Level of Umbilical Cord Blood: Is it related to Respiratory Distress Syndrome? Iranian journal of nephrology. 1 (3): 24-28.
51. Monafi M, Rabiee Pour S & Pourheidar B 2003. Evaluation of food consumption in pregnant women referring to health centers in Urmia. Medical journal of Urmia University of medical sciences. 14 (4): 9-15.
52. Moshfeghy Z, et al. 2020. The predictive value of selenium in diagnosis of gestational diabetes: a nested case-control study. International journal of general medicine. 13: 53-60.
53. Mostafa-Gharehbaghi M, et al. 2012. Determination of selenium in serum samples of preterm newborn infants with bronchopulmonary dysplasia using a validated hydride generation system. Biological trace element research. 147 (1): 1-7.
54. Nakayama SF, et al. 2019. Blood mercury, lead, cadmium, manganese and selenium levels in pregnant women and their determinants: the Japan Environment and Children’s Study (JECS). Journal of exposure science & environmental epidemiology. 29 (5):633-647.
55. Nazemi L, et al. 2012. Selenium status in soil, water and essential crops of Iran. Iranian journal of environmental health science & engineering. 9 (1): 1-8.
56. Nazemi L, et al. 2015. Comparison of maternal and umbilical cord blood selenium levels in low and normal birth weight neonates. Journal of family & reproductive health. 9 (3): 125.
57. Noormohammadi Isa, Mehdizadeh Abolfazl, Mandegar Mansoureh & Meamarzadeh Ali Reza 2004. Association of serum zinc and selenium concentration in the etiology of miscarriage in Iranian women. Medical science journal. 14 (2): 89-92.
58. Okunade KS, et al. 2018. Selenium deficiency and pregnancy outcome in pregnant women with HIV in Lagos, Nigeria. International journal of gynecology & obstetrics. 142 (2): 207-213.
59. Parast VM & Paknahad Z 2017. Antioxidant status and risk of gestational diabetes mellitus: a case-control study. Clinical nutrition research. 6 (2): 81.
60. Peirovifar A, Gharehbaghi MM, Abdulmohammad-Zadeh H, Sadegi GH & Jouyban A 2013. Serum selenium levels of the very low birth weight premature newborn infants with bronchopulmonary dysplasia. Journal of trace elements in medicine and biology. 27 (4): 317-321.
61. Pieczyńska J & Grajeta H 2015. The role of selenium in human conception and pregnancy. Journal of trace elements in medicine and biology. 29: 31-38.
62. Polanska K, et al. 2016. Selenium status during pregnancy and child psychomotor development-Polish Mother and Child Cohort study. Pediatric research. 79 (6): 863-869.
63. Rafraf M, Mahdavi R & Rashidi MR 2008. Serum selenium levels in healthy women in Tabriz, Iran. Food and nutrition bulletin. 29 (2): 83-86.
64. Rayman MP 2000. The importance of selenium to human health. Lancet. 356 (9225): 233-241.
65. Rayman MP 2008. Food-chain selenium and human health: emphasis on intake. British journal of nutrition. 100 (2): 254-268.
66. Rayman MP 2012. Selenium and human health. Lancet. 379 (9822): 1256-1268.
67. Sheykhi M, Paknahad Z & Hasanzadeh A 2015. Dietary nutrient intake and antioxidant status in preeclamptic women. Advanced biomedical research. 4: 183.
68. Sieniawska CE, Meniskov R & Delves HT 1999. Determination of total selenium in serum, whole blood and erythrocytes by ICP-MS. Journal of analytical atomic spectrometry. 14 (2): 109-112.
69. Solé-Navais P, et al. 2021. Maternal Dietary Selenium Intake during Pregnancy Is Associated with Higher Birth Weight and Lower Risk of Small for Gestational Age Births in the Norwegian Mother, Father and Child Cohort Study. Nutrients. 13 (1): 23.
70. Stoffaneller R & Morse NL 2015. A review of dietary selenium intake and selenium status in Europe and the Middle East. Nutrients. 7 (3): 1494-1537.
71. Tan LC, Nancharaiah YV, van Hullebusch ED & Lens PN 2018. Selenium: environmental significance, pollution, and biological treatment technologies. Biotechnology advances. 34 (5): 886-907.
72. Tara F, et al. 2010a. Selenium supplementation and the incidence of preeclampsia in pregnant Iranian women: a randomized, double-blind, placebo-controlled pilot trial. Taiwanese journal of obstetrics and gynecology. 49 (2): 181-187.
73. Tara F, et al. 2010b. Prooxidant-antioxidant balance in pregnancy: a randomized double-blind placebo-controlled trial of selenium supplementation. Journal of perinatal medcine. 38 (5): 473-478.
74. Vanderlelie J & Perkins A 2011. Selenium and preeclampsia: a global perspective. Pregnancy Hypertension. International journal of women's cardiovascular health. 1 (3-4): 213-224.
75. Wang X, et al. 2020. Selenium Nutritional Status of Rural Residents and Its Correlation with Dietary Intake Patterns in a Typical Low-Selenium Area in China. Nutrients. 12 (12): 3816.
76. Xia Y, et al. 2010. Optimization of selenoprotein P and other plasma selenium biomarkers for the assessment of the selenium nutritional requirement: a placebo-controlled, double-blind study of selenomethionine supplementation in selenium-deficient Chinese subjects. American journal of clinical nutrition. 92 (3): 525-531.
77. Zachara BA 2018. Selenium in complicated pregnancy. a review. Advances in clinical chemistry. 86: 157-178.
78. Zhong Q, Lin R & Nong Q 2018. Adiposity and serum selenium in US adults. Nutrients. 10 (6): 727.
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