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This meta-analysis examines the impact of vitamin D deficiency in over 28,000 pregnant women. The study found that vitamin D deficiency significantly increased the risk of low birth weight infants (LBWI) but showed no clear link to preterm birth or small-for-gestational-age (SGA) infants. Given the rise of vitamin D deficiency globally, especially in pregnant women, the study emphasises the need for regular monitoring and interventions. Further research with larger samples is recommended to better understand the impact of vitamin D deficiency on pregnancy outcomes.
Study overview
A Chinese meta-analysis reviewed 13 cohort studies from 8 countries between 2012 and 2021, involving 28,155 pregnant women with vitamin D deficiency and 8,580 with adequate levels. The study aimed to assess how vitamin D deficiency during pregnancy affects neonatal outcomes, only using data from Chinese and English sources.
Definitions of outcomes
Preterm birth refers to infants born before 37 weeks, and SGA refers to those with birth weights below the 10th percentile for their gestational age. LBWI are infants weighing less than 2,500 grams at birth. Adverse birth outcomes, such as preterm birth and LBWI, have been rising, contributing to neonatal mortality and higher risks of chronic diseases later in life.
Role of vitamin D in pregnancy
Vitamin D regulates hormones and cell cycle, playing a crucial role in pregnancy. Deficiency is linked to adverse outcomes like gestational diabetes, eclampsia, and miscarriage. It is affecting around 50% of the global population and more in pregnant women. Factors such as reduced outdoor activity, insufficient supplementation, and hormonal changes contribute to this deficiency during pregnancy. Foetuses are unable to produce vitamin D by themselves. A transfer across the placenta is necessary.
Neonatal outcomes
Of the studies, nine examined preterm birth and found no significant link to vitamin D deficiency at any stage of pregnancy. However, five studies showed that vitamin D deficiency significantly increased the risk of LBWI, particularly when the deficiency persisted throughout pregnancy. Nine studies also examined SGA but found no significant association with vitamin D deficiency. A subgroup analysis suggested that vitamin D deficiency throughout pregnancy may slightly increase the risk of SGA, though results were not statistically significant.
Conclusion
Vitamin D deficiency increases the risk of LBWI but has no significant effect on preterm birth or SGA. Further studies with larger samples are needed, and regular monitoring of vitamin D levels in pregnancy is recommended to improve neonatal outcomes.
Paper available at: Frontiers | The effect of vitamin D deficiency during pregnancy on adverse birth outcomes in neonates: a systematic review and meta-analysis (frontiersin.org)
Full list of authors: You, Z, Mei H., Zhang, Y., Song D., Zhang Y., & Liu C.
DOI: https://doi.org/10.3389/fped.2024.1399615
