Maternal Folic Acid Supplement Use, Folate Intake, and Preterm Birth Among Infants With Spina Bifida

Background We sought to assess the extent to which folic acid supplementation and dietary folate intake are associated with preterm delivery among infants with spina bifida. Methods We conducted a retrospective population‐based study using the National Birth Defects Prevention Study (NBDPS; 1999–2011) and the Birth Defects Study To Evaluate Pregnancy exposureS (BD‐STEPS; 2014–2019). We utilized robust Poisson regression to calculate the risk ratio (RR) and 95% confidence interval (CI) for the associations between preterm birth (< 37 weeks) and maternal use of folic acid‐containing supplements, dietary folate intake quartile, and a combined variable accounting for supplementation and dietary folate status. Results Among 1199 infants with spina bifida (1011 in NBDPS, 188 in BD‐STEPS), 217 (18.1%) were born preterm. There were no statistically significant associations between preterm birth and lack of supplementation (RR 1.24, 95% CI: 0.92–1.69) or maternal dietary folate intake quartile (RRs 1.12–1.39). The combination of lack of supplementation and low dietary folate intake had the strongest association with preterm birth (RR 1.73, 95% CI: 1.01–2.96), compared to women who took supplements and had higher dietary folate intake. Conclusions Our findings suggest a modestly elevated risk of preterm birth among infants with spina bifida born to women with the combination of no supplementation and low dietary folate intake. Future work confirming these findings and further investigating the timing of supplementation could help elucidate whether low folate intake is a risk factor for preterm birth in spina bifida–affected pregnancies.