A related editorial notes the main analysis (risk of SGA) was based only on 880 participants from six smaller studies, and that it may well have been a chance finding. The meta-analysis included multiple outcomes, which increases the risk of detecting false-positive associations, and this multiple testing was not accounted for. The findings on infant growth should additionally be interpreted with caution, as they were based on only 2 studies using different dosing regimens, and heterogeneity was high. They go on to discuss further limitations to the analysis and conclude that “the main finding that may be drawn from the meta-analysis …. is that prenatal vitamin D supplementation increases neonatal 25(OH)D and no adverse effects have been found. Further well-powered double-blind RCTs with predefined primary end points are warranted to decide evidence-based health recommendations on vitamin D supplementation.”
All adults need 10 micrograms of vitamin D a day, and should consider taking a supplement containing this amount. Current UK guidance states that it is important to maintain adequate vitamin D during pregnancy and breastfeeding, and that women may choose to take up to 10 micrograms of vitamin D a day during these periods, particularly if they have specific risk factors for vitamin D deficiency.