Timing matters: when do primiparous and multiparous pregnant women initiate folic acid supplementation, and who initiates it too late?

Background: Women are recommended to take folic acid supplements (FAS) periconceptionally to prevent neural tube defects, but the low levels of FAS uptake are poorly understood. This study aimed to determine how parity, pregnancy planning and other maternal factors affect the timing of FAS initiation. Method: We used data from a representative sample of 966 pregnant women from the Northern Ireland Baby Hearts study. Questionnaire responses on health behaviours, including FAS, were linked to maternity and area-based deprivation data. Logistic regression assessed determinants of FAS initiation preconception. Time-varying Cox regression assessed associations between initiation postconception and pregnancy-related milestones. Results: Forty-one per cent of women initiated FAS preconception. Lower odds of preconception initiation were associated with multiparity (adjusted OR 0.47 (0.32 to 0.68)), unplanned pregnancy (adjusted OR 0.08 (0.05 to 0.13)), deprivation and consuming a low folate diet. Higher odds were associated with fertility treatment and previous pregnancy loss. Forty-seven per cent of women initiated FAS postconception, mainly after pregnancy recognition (median 5 weeks), including 34.1% of those who planned their pregnancy. For primiparous women with unplanned pregnancies, the first health service contact (median 7 weeks) further increased FAS initiation. Conclusion: Many women, even multiparous women with previous pregnancy experience and women who planned their pregnancies, are initiating FAS after pregnancy recognition. This shows awareness of FAS benefits, but is too late to prevent neural tube defects. Public health interventions need to go beyond awareness to address motivation and opportunity for FAS, and pay more attention to multiparous women.