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Do maternal urinary iodine concentration or thyroid hormones within the normal range during pregnancy affect growth parameters at birth? A systematic review and meta-analysis.
Nazeri, P, Shab-Bidar, S, Pearce, EN, Shariat, M
Nutrition reviews. 2020;(9):747-763
Abstract
CONTEXT Iodine, an essential constituent of thyroid hormones, is required for proper growth and development. OBJECTIVE To investigate whether growth parameters at birth are associated with maternal urinary iodine concentration (UIC) or normal ranges of thyroid hormones during pregnancy. DATA SOURCES Using the Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) guidelines, electronic databases (namely, MEDLINE, Web of Science, the Cochrane Library, Scopus, and Google Scholar) were searched between January 1988 and November 2018 to identify relevant articles. DATA EXTRACTION Data from the studies included were independently extracted by 2 investigators using standardized forms developed for this review. DATA ANALYSIS The pooled mean birth weight, length, and head circumference values, and 95% confidence intervals were estimated in newborns born to women with UIC < 150 and UIC ≥150 μg/L during pregnancy. Possible linear or nonlinear associations between maternal UIC and the aforementioned anthropometric measures were evaluated. A narrative synthesis of the data was performed for thyroid hormones with levels within the normal range. RESULTS Of the 123 studies identified, 11 were eligible for inclusion in the meta-analysis. The pooled mean birth weight, length, and head circumference in newborns whose mothers had UIC < 150 μg/L vs UIC ≥150 μg/L were 2898 g vs 2900 g (P = 0.970), 49.6 cm vs 49.4 cm (P = 0.880), and 34.0 cm vs 34.1 cm (P = 0.933), respectively. Dose-response meta-analyses revealed no significant linear or nonlinear associations between maternal UIC during pregnancy and anthropometric measures at birth. Among the different thyroid function parameters evaluated, high-normal values of maternal free thyroxine and thyrotropin during pregnancy were inversely associated with neonatal birth weight. CONCLUSION This systematic review showed that birth weight may be affected by even mild variations in the normal concentrations of maternal thyroid hormones. However, in the current meta-analysis, birth anthropometric measures were not associated with maternal UIC during pregnancy.
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Improvement of glucose metabolism in pregnant women through probiotic supplementation depends on gestational diabetes status: meta-analysis.
Łagowska, K, Malinowska, AM, Zawieja, B, Zawieja, E
Scientific reports. 2020;(1):17796
Abstract
The aim of this study was to assess the effects of probiotic and synbiotic supplementation on glucose metabolism in pregnant women using data from randomized controlled trials. Furthermore, this meta-analysis examines whether the observed effects depend on the presence or absence of gestational diabetes mellitus (GDM), and if the effect is dependent on the type of supplement used (probiotic or synbiotic). We performed a literature search of databases (Medline, Scopus, Web of Knowledge, and Cochrane Library) and identified all relevant randomized controlled trials (RCTs) published prior to May 2019. We compared the effects of probiotic supplementation with the administration of placebos in pregnant women with and without GDM. The systematic review and meta-analysis protocol were registered in the International Prospective Register of Systematic Reviews as number CRD 42019111467. 1119 study participants from 15 selected studies were included. The participants in four studies did not have GDM (being recruited to the study before week 20 of pregnancy) and the participants in the rest of the studies were diagnosed with GDM between weeks 24 and 28 of gestation. The meta-analysis showed that supplementation lowers serum glucose, insulin levels, and HOMA-IR index, but only in pregnant women with GDM. Moreover, both probiotics and synbiotics lower serum insulin level and HOMA-IR index, but the glucose lowering effect is specific only to probiotics and not synbiotics. Probiotic supplementation may improve glucose metabolism in pregnant women with GDM. There is a need for more RCT studies with larger groups to better estimate this effect.
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Maternal hemoglobin concentrations across pregnancy and maternal and child health: a systematic review and meta-analysis.
Young, MF, Oaks, BM, Tandon, S, Martorell, R, Dewey, KG, Wendt, AS
Annals of the New York Academy of Sciences. 2019;(1):47-68
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Abstract
Maternal anemia is a well-recognized global health problem; however, there remain questions on specific hemoglobin (Hb) thresholds that predict health risk or protection for mother and child. We conducted a systematic review and meta-analysis to examine the associations of maternal Hb concentrations with a range of maternal and infant health outcomes, accounting for the timing of measurement (preconception, and first, second, and third trimesters), etiology of anemia, and cutoff category. The systematic review included 272 studies and the meta-analysis included 95 studies. Low maternal Hb (<110 g/L) was associated with poor birth outcomes (low birth weight, preterm birth, small-for-gestational-age (SGA), stillbirth, and perinatal and neonatal mortality) and adverse maternal outcomes (postpartum hemorrhage, preeclampsia, and blood transfusion). High maternal Hb (>130 g/L) was associated with increased odds of SGA, stillbirth, preeclampsia, and gestational diabetes. Relationships varied by the timing of measurement and cutoff category (stronger associations with lower cutoffs); limited data were available on anemia etiology. There were insufficient data for other maternal outcomes and long-term child health outcomes. Current data are insufficient for determining if revisions to current Hb cutoffs are required. Pooled high-quality individual-level data analyses, as well as prospective cohort studies, would be valuable to inform the reevaluation of Hb cutoffs.
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Maternal Thyroid Function in Early Pregnancy and Child Attention-Deficit Hyperactivity Disorder: An Individual-Participant Meta-Analysis.
Levie, D, Korevaar, TIM, Mulder, TA, Bath, SC, Dineva, M, Lopez-Espinosa, MJ, Basterrechea, M, Santa-Marina, L, Rebagliato, M, Sunyer, J, et al
Thyroid : official journal of the American Thyroid Association. 2019;(9):1316-1326
Abstract
Background: Thyroid hormone is essential for optimal fetal brain development. Evidence suggests that both low and high maternal thyroid hormone availability may have adverse effects on child neurodevelopmental outcomes, but the effect on behavioral problems remains unclear. We studied the association of maternal thyrotropin (TSH) and free thyroxine (fT4) concentrations during the first 18 weeks of pregnancy with child attention-deficit hyperactivity disorder (ADHD). Methods: A total of 7669 mother-child pairs with data on maternal thyroid function and child ADHD were selected from three prospective population-based birth cohorts: INfancia y Medio Ambiente (INMA; N = 1073, Spain), Generation R (N = 3812, The Netherlands), and Avon Longitudinal Study of Parents and Children (ALSPAC; N = 2784, United Kingdom). Exclusion criteria were multiple pregnancy, fertility treatment, usage of medication affecting the thyroid, and pre-existing thyroid disease. We used logistic regression models to study the association of maternal thyroid function with the primary outcome, ADHD, assessed via the Diagnostic and Statistical Manual of Mental Disorders, fourth edition (DSM-IV) criteria by parents and/or teachers at a median child age of 4.5 to 7.6 years, and with the secondary outcome, an ADHD symptom score above the 90th percentile. Effect modification by gestational age and sex was tested with interaction terms and stratified analyses. Results: Overall, 233 (3%) children met the criteria for ADHD. When analyzed continuously, neither fT4 nor TSH was associated with a higher risk of ADHD (odds ratio [OR] 1.1, 95% confidence interval [CI 1.0-1.3], p = 0.060 and OR 0.9 [CI 0.9-1.1], p = 0.385, respectively) or with high symptom scores. When investigating effect modification by gestational age, a higher fT4 was associated with symptoms above the 90th percentile but only in the first trimester (for fT4 per 1 SD: OR 1.2 [CI 1.0-1.4], p = 0.027). However, these differential effects by gestational age were not consistent. No significant effect modification by sex was observed. Conclusions: We found no clear evidence of an association between maternal thyroid function and child ADHD.
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Gestational age and maternal status of DHA and other polyunsaturated fatty acids in pregnancy: A systematic review.
Wilson, NA, Mantzioris, E, Middleton, PT, Muhlhausler, BS
Prostaglandins, leukotrienes, and essential fatty acids. 2019;:16-31
Abstract
INTRODUCTION Maternal diet is important in determining omega-3 DHA status however there is limited knowledge of other factors influencing maternal omega-3 concentrations during pregnancy. The primary objective of this systematic review and meta-analysis was to evaluate whether maternal DHA status changed across gestation. Changes in levels of other key polyunsaturated fatty acids were also investigated. MATERIALS AND METHODS The Medline, Embase, Amed, and CINAHL databases were searched. Included studies reported measures of maternal omega-3 status in at least two pregnancy trimesters. RESULTS Thirteen studies were included in the final analyses. Absolute omega-3 DHA concentrations increased across gestation, but decreased as a proportion of total lipids. DISCUSSION Our findings are consistent with previous observations of increases in lipid mobilisation, coupled with preferential transfer of DHA to the fetus, with advancing gestation. However the number of eligible studies was small and further investigations are required.
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Glucose responses to acute and chronic exercise during pregnancy: a systematic review and meta-analysis.
Davenport, MH, Sobierajski, F, Mottola, MF, Skow, RJ, Meah, VL, Poitras, VJ, Gray, CE, Jaramillo Garcia, A, Barrowman, N, Riske, L, et al
British journal of sports medicine. 2018;(21):1357-1366
Abstract
OBJECTIVE To perform a systematic review and meta-analysis to explore the relationship between prenatal exercise and glycaemic control. DESIGN Systematic review with random-effects meta-analysis and meta-regression. DATA SOURCES Online databases were searched up to 6 January 2017. STUDY ELIGIBILITY CRITERIA Studies of all designs were included (except case studies and reviews) if they were published in English, Spanish or French, and contained information on the population (pregnant women without contraindication to exercise), intervention (subjective or objective measures of frequency, intensity, duration, volume or type of acute or chronic exercise, alone ('exercise-only') or in combination with other intervention components (eg, dietary; 'exercise+cointervention') at any stage of pregnancy), comparator (no exercise or different frequency, intensity, duration, volume and type of exercise) and outcome (glycaemic control). RESULTS A total of 58 studies (n=8699) were included. There was 'very low' quality evidence showing that an acute bout of exercise was associated with a decrease in maternal blood glucose from before to during exercise (6 studies, n=123; mean difference (MD) -0.94 mmol/L, 95% CI -1.18 to -0.70, I2=41%) and following exercise (n=333; MD -0.57 mmol/L, 95% CI -0.72 to -0.41, I2=72%). Subgroup analysis showed that there were larger decreases in blood glucose following acute exercise in women with diabetes (n=26; MD -1.42, 95% CI -1.69 to -1.16, I2=8%) compared with those without diabetes (n=285; MD -0.46, 95% CI -0.60 to -0.32, I2=62%). Finally, chronic exercise-only interventions reduced fasting blood glucose compared with no exercise postintervention in women with diabetes (2 studies, n=70; MD -2.76, 95% CI -3.18 to -2.34, I2=52%; 'low' quality of evidence), but not in those without diabetes (9 studies, n=2174; MD -0.05, 95% CI -0.16 to 0.05, I2=79%). CONCLUSION Acute and chronic prenatal exercise reduced maternal circulating blood glucose concentrations, with a larger effect in women with diabetes.