The effectiveness of mandatory folic acid fortification compared with pre-fortification periods on reducing neural tube defects (NTDs): a systematic review and meta-analysis

Neural tube defects (NTDs) are serious birth defects of the brain and spine, with folic acid supplementation and fortification recognized as effective prevention strategies. While both approaches are widely used, there remains a debate about the relative effectiveness of mandatory folic acid fortification versus supplementation alone. This systematic review and meta-analysis assess the impact of mandatory folic acid fortification compared with pre-fortification periods on NTDs. A comprehensive literature search was conducted to identify observational studies evaluating the impact of mandatory folic acid fortification on NTDs prevalence. Fourteen studies, encompassing over 33 million participants, met the inclusion criteria. The meta-analysis calculated pooled risk ratios (RR) to compare the effectiveness of fortification to the comparison group. Subgroup analyses were performed based on geographic location to explore potential regional variations in outcomes. The pooled analysis revealed that mandatory folic acid fortification was associated with a 44% reduction in the risk of NTDs (RR = 0.56). Subgroup analyses demonstrated region-specific benefits: North American studies showed a 54% reduction in NTDs risk (RR = 0.46), while South American studies reported a 38.8% reduction (RR = 0.61). Therefore, mandatory folic acid fortification significantly reduces the risk of NTDs compared to pre-fortification. Continued implementation, alongside supplementation and rigorous monitoring, is crucial to further reduce the global incidence of NTDs.