Starting daily folic acid supplementation at 0.4 mg before pregnancy and continuing through the first trimester

Taking one folic acid pill daily before and during early pregnancy can cut the risk of neural tube defects in babies by roughly 70%. These defects include conditions like anencephaly and spina bifida. For women who’ve already had a child with such a defect, this regimen reduces the likelihood of a repeat occurrence to about one third of the original risk.

A bottle costs only a few dozen yuan. Rural women receive it for free through the national folic acid supplementation program. The real challenge is remembering to take one pill every day.

A Cochrane systematic review pooled data from 5 trials involving 6,708 deliveries, rating the evidence as high quality. Daily folic acid intake before and during pregnancy lowered the relative risk of fetal neural tube defects to 0.31 (95% CI 0.17–0.58), a reduction of roughly 70%. For women with a prior child affected by neural tube defects, the relative risk dropped to 0.34 (95% CI 0.18–0.64), equating to a one third reduction in risk. No difference in effectiveness was observed between 0.4 mg and higher doses, nor between folic acid alone and multivitamin supplements.

The key point is to start taking folic acid before pregnancy. A fetus’s neural tube closes within 28 days of conception; by the time a pregnancy is detected, most of this window has already passed. Therefore, if you’re planning to conceive, begin supplementation three months in advance. The same review found no clear evidence that folic acid prevents cleft lip and palate, congenital heart disease, or miscarriage — so don’t expect it to address these issues.

De-Regil LM, Peña-Rosas JP, Fernández-Gaxiola AC, Rayco-Solon P (2015). Effects and safety of periconceptional oral folate supplementation for preventing birth defects. Cochrane Database of Systematic Reviews, (12), CD007950. https://doi.org/10.1002/14651858.CD007950.pub3；卫生部办公厅 (2010). 2010 年增补叶酸预防神经管缺陷项目管理方案. https://www.nhc.gov.cn/wjw/gfxwj/201006/22a0b4d4651e4b6d896453d443d9f79d/files/1733384846754_72260.doc；Centers for Disease Control and Prevention. About Folic Acid. https://www.cdc.gov/folic-acid/about/index.html