Folic acid is currently considered to be the standard of care for primary and secondary prevention of spina bifida, but the mechanisms underlying folic acid's benefits are unknown. One hypothesis is that folic acid changes DNA methylation and transcription of genes important in neural tube closure.

In this study, the investigators will evaluate how DNA methylation of genes associated with neural tube closure changes after a short course of standard-of-care folic acid supplementation. In addition, the investigators will assess whether environmental arsenic exposure modifies the effects of folic acid on the methylosome.

The investigators will encourage women who have recently had a pregnancy affected by spina bifida to take daily folic acid supplements for three months. Folic acid supplementation is considered standard of care for primary and secondary prevention of spina bifida. The investigators will compare DNA methylation in blood and folate levels before and after folic acid use.

Inclusion Criteria:

• Women (18+) with a prior pregnancy affected by spina bifida
• Available for required study visits

Exclusion Criteria:

• Personal history of diabetes or gestational diabetes
• Current anticonvulsant medication use
• History of pregnancy affected by identified genetic syndrome associated with neural tube defect such as Trisomy 18
• Current pregnancy
• Abnormal peripheral blood film results (suggestive of megaloblastic anemia/B12 deficiency.)