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

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 5 trials and 6708 births and rated the evidence high quality. Daily folic acid before and during pregnancy cut fetal neural tube defect risk to relative risk RR 0.31 (95% CI 0.17 to 0.58, the plausible range), about a seven-tenths reduction. For people who had already had a child with a neural tube defect, the risk of another affected child was relative risk RR 0.34 (95% CI 0.18 to 0.64), about one third of the original. By subgroup, no clear effect difference was detected between 0.4 mg and higher doses, or between folic acid alone and a multivitamin. The Ministry of Health’s 2010 folic acid supplementation program plan states that rural women preparing to conceive receive free folic acid, “taken from 3 months before pregnancy through the first 3 months of pregnancy,” as 0.4 mg tablets. The US Centers for Disease Control and Prevention notes that neural tube defects form in the first few weeks of pregnancy, often before you know you are pregnant

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

The key is to start before pregnancy. Neural tube defects form in the first few weeks; if you wait until a positive test, it may already be late. So if you plan to have a child, start 3 months ahead, as the domestic program does. The same pooled review found no clear effect of folic acid on cleft lip and palate, congenital heart disease, or miscarriage — do not count on it for those. Pregnant people on a fully plant-based diet also need vitamin B12 every day; see Section 20, Item 14 (if you eat plant-based, take vitamin B12 daily). If you are still undecided about when to have a child, the age account is in Section 18, Item 7 (waiting a few more years to have a child).