Objective: To find out the prevention effects of folic acid supplements during different pregnancy periods on neural tube defects (NTDs) and the relationship of folic acid supplements with the other NTDs' primary preventive measures.
Methods: A 1:1 case-control study was conducted. Four hundred and fifty-nine women who delivered or gestate infants/fetuses with NTDs in the last two years were randomly selected as cases and were matched with women who delivered babies without obvious birth defects as controls.
Results: For anencephaly, folic acid supplementation during the periconceptional period and preconceptional period has a 57-83% reduction in risk of NTDs(ORs ranged from 0.17 to 0.43). For spina bifida, folic acid supplementation during the periconceptional period has a 79% reduction in risk of NTDs (OR = 0.21). For encephalocele, folic acid supplementation during the periconceptional period has a 67% reduction in risk of NTDs (OR = 0.33). The prevention effects on NTDs were significant when these preventive measures combined with folic acid supplements during the periconceptional period, with OR 0.04, 0.07, 0.10 and 0.11.
Conclusion: The specific effects of folic acid supplementation during different periods show the reduction in the risk of NTDs, anencephaly, spina bifida, encephalocele. During periconceptional period, folic acid supplements have preventive effects on all NTDs' subtypes.
Keywords: Anencephaly; folic acid; neural tube defects; periconceptional period; preventive measures; spina bifida.