Preconception Folic Acid and Multivitamin Supplementation for the Prevention of Neural Tube Defect: An Umbrella Review of Systematic Review and Meta-analysis.

Background: Previous reviews explored the association between maternal use of folic acid and multivitamin supplements and risk of neural tube defect (NTD) in children, with no definitive conclusion. These reviews had produced contradictory results, and there had been no umbrella review. Therefore, the objective of this umbrella review is to combine the inconsistent data on the effect of prenatal folic acid and/or multivitamin supplementation for the prevention of NTD in offspring.

Methods: Using the PRISMA guideline, PubMed, Embase, Scopus, Web of Sciences, Cochrane Database of Systematic Reviews, Scopus, and Google Scholar reported that the effects of folic acid and/or multivitamin supplementation for the prevention of NTD in offspring were searched. The quality of the included studies was assessed using Assessment of Multiple Systematic Reviews (AMSTAR). A weighted inverse variance random-effects model was applied to find the pooled estimates. The subgroup analysis, heterogeneity, publication bias, and sensitivity analysis were also assessed.

Result: Ten SRM with 296,816 study participants were included. The random-effects model analysis from 10 included systematic review and meta-analysis revealed that the pooled effect of either folic acid or multivitamin supplementation for the prevention of NTD globally is found to be 0.43 (95% CI: 0.29, 0.58) (I2 = 93.50%; p ≤0.001). In the subgroup analysis, the pooled effect was found to be 0.23 (0.09, 0.37) in folic acid group, while this estimate is 0.63 (0.53, 0.72) and 0.61 (0.46, 0.75) in groups who took multivitamin. The pooled effect of prevention of NTD was found to be 0.50 (0.34, 0.66) in SRMs aimed at occurrence prevention (primary prevention) group, while this estimate is 0.20 (-0.01, 0.41) among SRMs, which aimed at reoccurrence (secondary) prevention, and 0.61 (0.46, 0.75) among those SRMs aimed to assess the effect folic acid or multivitamin for the prevention of both occurrence and reoccurrence. The pooled effect of either folic acid or multivitamin supplementation for the prevention of NTD was found to be 0.45 (0.03, 0.87) in SRMs of observational studies, while this estimate is 0.43 (0.32, 0.54) among SRMs of randomized controlled trials.

Conclusion: This umbrella review of systematic review and meta-analysis found that prenatal folic acid and/or multivitamin supplementation was associated with a 57% reduction in NTD. Participants who took folic acid supplementation were associated with a slightly higher (77%) percentage of reduction in NTD compared with those who took multivitamin (37%). Reductions of 80% and 50% were observed for reoccurrence and occurrence prevention of NTD. Reductions of 57% and 55% of NTD have been found in SRM of RCTs and observational studies. This umbrella review revealed that both folic acid and multivitamin were associated with significantly lower levels of NTD in children. Considering the incorporation of those supplements in NTD prevention strategies during the preconception period is recommended. More large-scale prospective cohort and RCTs are needed to understand the protective effect of multivitamins and/or folic acid on NTD risk addressing the molecular mechanisms and to determine the optimal dose, duration, and timing of maternal multivitamin and folic acid intake for best child NTD risk reduction.