Does Maternal High-dose Vitamin D Supplementation During Pregnancy Increase Linear Growth Among Infants at One Year? - A Systematic Review and Meta-analysis

Background: In pregnancy, maternal vitamin D deficiency has been associated with adverse birth outcomes worldwide and has become a major public health concern. However, the linkage between maternal prenatal vitamin D status and post-natal linear growth, particularly in infancy, is inconclusive and ambiguous. Objective: This study aims to systematically identify, appraise, and synthesize available evidence regarding the effect of maternal vitamin D supplementation on infants’ linear growth at one year. Methods: A systematic electronic search of Medline and Embase databases was undertaken from the OVID platform. The risk of bias in the selected studies was assessed using the risk of bias (RoB) tool introduced and recommended by the Cochrane Collaboration. Results: A quantitative synthesis (meta-analysis) was conducted using RevMan. After screening, only two studies fulfilled the eligibility criteria, comprising a total of 593 infants: (296 from mothers receiving vitamin D and 297 from mothers receiving placebo). One RCT found a 0.8 cm gain in length whereas the second RCT found infants to be 0.23 cm shorter compared to their placebo counterparts. A meta-analysis also could not detect a significant difference in length. However, the pooled result favored infants (0.19 cm taller) born to mothers receiving prenatal vitamin D. Conclusion: The quality of overall evidence for the outcome ‘infant length at 1 year’-as assessed using the GRADE approach was low. Maternal high-dose vitamin D supplementation during pregnancy increases linear growth in infants at 12 months of age, but, this increase is very small and not statistically significant.