27-001 · EVIDENCE A · SOURCE-SENSITIVE
Starting daily folic acid supplementation at 0.4 mg before pregnancy and continuing through the first trimester
准备怀孕就开始每天补 0.4 毫克叶酸，一直吃到孕早期满 3 个月
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.
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
Move “Starting daily folic acid supplementation at 0.4 mg before pregnancy and continuing through the first trimester” to Future Me's calendar
The excuse
Future Me has a clearer calendar, more patience, and apparently the same responsibilities.
What feels good now
Today I keep a few minutes, a bit of persistence and avoid interrupting my default routine.
What the source says
The source summarizes the return this way: “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.” Evidence grade A. The original states the population, caveats, and sources; this is not a personal forecast.
Use the original facts and limits. For an urgent medical, safety, financial, or legal issue, contact a qualified local professional or service.
THE ENGLISH EDITION
Original recommendation and evidence
1. Starting daily folic acid supplementation at 0.4 mg before pregnancy and continuing through the first trimester
Cost: 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.
In plain terms: 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.
Benefit: 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.
Evidence grade: A
Notes: 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.
Sources: 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>
Read the complete Chinese source and notes
1. 准备怀孕就开始每天补 0.4 毫克叶酸，一直吃到孕早期满 3 个月
成本: 几十元一瓶。农村妇女不用花钱，国家的免费增补叶酸项目会发。每天吃一粒，难在天天记得住
说人话: 怀孕前后每天吃一粒叶酸，孩子出现神经管缺陷的概率大约能降七成。神经管缺陷就是无脑儿、脊柱裂这一类的出生缺陷。已经生过一个这样的孩子的人，再生一个还出问题的概率，大约降到原来的三分之一。
收益: Cochrane 系统综述把 5 项试验、6708 例分娩合起来一起算，证据质量评为高。怀孕前后每天补叶酸，胎儿神经管缺陷的风险 RR 0.31（95% CI 0.17 至 0.58，可信范围），约降低七成。已经生过神经管缺陷孩子的人，再生一个又出问题的风险 RR 0.34（95% CI 0.18 至 0.64），降到原来的三分之一左右。按人群分组来看，0.4 毫克和更高的剂量效果没有差别。单独吃叶酸和吃复合维生素，效果也没有差别
证据等级: A
来源: 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>
备注: 关键是「怀孕前就开始吃」。胎儿的神经管在受孕后 28 天内就长合了。等你测出怀孕再吃，这段时间已经过去大半。所以打算要孩子，就提前 3 个月开始吃。同一篇汇总研究里，叶酸对唇腭裂、先天性心脏病、流产都没有明确效果，别指望它治别的。吃全素的孕妇还要每天补维生素 B12，见第 20 节第 14 条（吃素就每天补维生素 B12）
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