Folic acid in pregnancy

Why is folic acid recommended in pregnancy?

The basis of the recommendation is randomized trials that answer two separate questions: does folic acid reduce recurrence in women who previously had a pregnancy with a neural tube defect, and does it reduce first occurrence of a defect? In both questions, results favoring supplements containing folic acid have been reported.

Recurrence (MRC, 1991). The Medical Research Council trial is a randomized, double-blind trial with a factorial design conducted at 33 centers in seven countries. 1,817 high-risk women who had previously had a pregnancy with a neural tube defect were divided into groups receiving folic acid, a mixture of seven other vitamins, both, or neither. Of 1,195 pregnancies with known outcome, 27 had a defect: 6 cases in the folic acid groups and 21 in the other two groups (72% protective effect; RR 0.28; 95% CI 0.12–0.71). The other vitamins had no significant protective effect (RR 0.80; 0.32–1.72). The authors state that no demonstrable harm was seen for folic acid, but that the power to detect rare or mild side effects is limited. ^[1]

First occurrence (Czeizel and Dudás, 1992). In this trial, women planning pregnancy (mostly first pregnancies) took a single tablet daily from at least one month before until the date of the second missed period: either a mixture of 12 vitamins, 4 minerals and 3 trace elements containing 0.8 mg of folic acid, or a trace element supplement. Pregnancy was confirmed in 4,753 women; the outcome was known in 2,104 (vitamin) and 2,052 (trace element) women. Neural tube defects were seen in 6 cases in the trace element group and 0 in the vitamin group (P = 0.029). Congenital malformations were 22.9 per 1,000 births in the trace element group and 13.3 in the vitamin group (P = 0.02); cleft lip or palate was not reduced. ^[2] Because what was given was a multi-component supplement, this trial does not attribute the effect to folic acid alone.

Why is starting before pregnancy recommended?

The CDC reports that adequate folate is required in early pregnancy for the neural tube, and that folic acid use before pregnancy and in early pregnancy lowers the chance of neural tube defects. According to the CDC’s page for clinicians, for patients planning pregnancy who are not using folic acid, it is recommended that a vitamin containing folic acid be started at least 1 month before conception; waiting for the first prenatal visit does not prevent neural tube defects. ^[4]

In 2023, the USPSTF concluded that folic acid supplementation in people planning to become pregnant or who could become pregnant provides “high certainty of substantial net benefit” for preventing neural tube defects; it recommends supplements containing 0.4–0.8 mg (400–800 µg) of folic acid daily with a grade A. The body also reports that there is adequate evidence that folic acid supplementation in usual amounts is not associated with serious harm. ^[3]

What do guidelines say about start time and duration?

The bodies draw a similar framework, but their wording is not exactly the same. The table below places each body’s own wording side by side.

NICE also states that folic acid supplementation is important even when foods (including flour) are fortified with folic acid. ^[5]

What do guidelines say for high-risk groups?

The general recommendation is the same for all women; in some situations, guidelines mention a higher amount of folic acid. These amounts are prescribed by a physician and their timing is determined according to the person; what follows is guideline wording, not a personal plan.

• NICE (2025): recommends giving 5 mg/day of folic acid to people at increased risk of a neural tube defect or another congenital malformation. Examples: a history of neural tube defect in the person or their partner or in the family, a neural tube defect or malformation in a previous pregnancy, type 1 or type 2 diabetes, a blood disorder requiring folic acid (such as sickle cell anemia, thalassemia) and medicines affecting folic acid absorption or metabolism (such as antiepileptics, HIV medicines). NICE states that in people with a BMI of 25 kg/m² or above and in people with increased risk of preeclampsia, going above 400 µg is not necessary if the factors in this list are absent. ^[5]
• CDC: recommends 4,000 µg of folic acid per day for women whose previous pregnancy had a neural tube defect and who are planning a new pregnancy; it states that this is started 1 month before trying to conceive and continued through the first 3 months of pregnancy; for those not planning pregnancy, the general 400 µg recommendation applies. ^[4]
• Turkish Ministry of Health (2026): states that in groups at high risk for neural tube defects, such as people using antiepileptic medicines, those with a history of a pregnancy with a neural tube defect, and those with diabetes or obesity, a high dose (4–5 mg/day) started 3 months before pregnancy is used for preventing neural tube defects. ^[6]

The difference between bodies is visible: for example, while the Ministry guideline lists obesity among high-risk groups, NICE states that a BMI of 25 and above alone does not require a high dose. In such a situation, which approach applies is determined by the physician assessing all of the person’s risk factors.

What is the situation in Türkiye?

The Turkish Ministry of Health Prenatal Care Management Guideline (2026) contains the general 400–800 µg recommendation above and a separate high-dose statement for high-risk groups. ^[6]

A 2020 report in the Türk Halk Sağlığı Dergisi whose title includes “Ministry of Health recommendations” reports that folate intake in women of childbearing age in Türkiye falls below the daily requirement and recommends that regulation be introduced for fortifying flour with iron and folic acid; according to the report, these recommendations had been submitted to the Ministry of Agriculture and Forestry, but no regulation had been made as of the date of the report. ^[7] In the Food Fortification Initiative’s Türkiye profile, fortification legislation for wheat, maize and rice is listed as “None”. ^[8] This data belongs to a civil-society initiative and is not an official Turkish document; the absence of a listed mandatory flour fortification regulation is consistent with the report’s call for regulation.

Common misunderstandings

• “Folic acid is needed only in pregnancy.” The body needs folate at every age; the pre-pregnancy recommendation is aimed at preventing neural tube defects. General reference values are on the folic acid main page.
• “Starting when pregnancy is learned is enough.” The CDC states that starting at the first prenatal visit will not prevent neural tube defects. NICE describes, if not started earlier, starting as early as possible after the first positive test and continuing for the first 12 weeks. ^{[4] [5]}
• “Folic acid prevents all birth defects.” In the trials, the effect has been shown for neural tube defects; in the Czeizel trial, cleft lip or palate was not reduced with the multi-component supplement. ^[2]
• “Methylfolate is safer or more effective.” The evidence for neural tube defects comes from supplements containing folic acid; details are on a separate page.

This guide does not recommend personal doses; if there is a pregnancy plan, chronic disease or medication use, the amount and duration of folic acid are determined by the relevant physician.