Why Is Folic Acid Recommended Before and During Pregnancy?

The CDC recommends 400 micrograms (mcg) of folic acid daily for people who could become pregnant because it is associated with a lower chance of neural tube defects, serious birth defects of the brain and spine that form very early in pregnancy, often before a person knows they are pregnant. This article explains how folic acid differs from folate, why timing matters, who may need a different amount, what to ask your clinician, and which symptoms need urgent care.

Why folic acid is recommended before and during pregnancy

Folic acid is the synthetic form of folate, a B vitamin your cells use to make DNA and to divide. Early pregnancy is a period of very fast cell division. Folate is one of several nutrients that support this process, and low folate intake is associated with a higher chance of neural tube defects.

The neural tube is the structure that becomes the baby's brain and spinal cord. It closes during the first weeks after conception. If it does not close fully, the result can be a neural tube defect such as spina bifida (the spine does not close completely) or anencephaly (major parts of the brain and skull do not develop). MedlinePlus (NIH) describes birth defects as structural changes present at birth, and neural tube defects are among the serious ones.

Population-level folic acid fortification and supplementation programs have been associated with fewer neural tube defects (see the CDC page on folic acid). Folic acid does not remove all risk. Neural tube defects can still occur in people who take it, and several genetic and environmental factors contribute.

Why timing matters: the weeks before a positive test

The neural tube closes early, often before a missed period or a positive pregnancy test. That is why advice usually starts before pregnancy rather than after the test turns positive. If you are trying to conceive, or could become pregnant, many clinicians recommend starting folic acid ahead of time and continuing through pregnancy. The CDC page on folic acid advises starting at least 1 month before conception.

Many pregnancies are not planned. This is part of why folic acid advice is often given to anyone who could become pregnant. If you learn you are pregnant and have not been taking it, starting then is still reasonable. Tell your prenatal clinician so they can advise on the amount and form. Our separate article on whether you need a prenatal vitamin before you get pregnant covers the broader vitamin question.

Folate, folic acid, and what is in your food

These terms are often mixed up.

• Folate is the form found naturally in foods such as leafy green vegetables, beans, lentils, citrus fruit and avocado.
• Folic acid is the synthetic form used in supplements and in fortified foods.
• Methylfolate and similar products are marketed as alternative forms. Ask your clinician whether a particular product is appropriate for you rather than assuming it is equivalent.

In the United States, many enriched breads, pastas, rice and breakfast cereals are fortified with folic acid. Even so, diet alone may not supply enough for some people, and food folate is generally absorbed less fully than folic acid from a supplement. Cooking can also reduce the folate in some foods. For this reason, clinicians often recommend a supplement in addition to a varied diet rather than relying on food alone.

Check labels. A standalone folic acid tablet and a prenatal vitamin can both contain it, and taking several products at once can add up. Your pharmacist can help you add up the total from all the products you take.

How much folic acid, and who may need a different amount

Most people who could become pregnant are advised to take 400 micrograms (mcg) of folic acid daily. The CDC advises that everyone who could become pregnant get 400 mcg every day, from a supplement or fortified food in addition to a varied diet. Most prenatal vitamins contain at least this amount, and the product label shows what each tablet contains. Your clinician can tell you whether a different amount fits your history.

The National Academies' tolerable upper intake level for synthetic folic acid in adults is 1,000 mcg per day from supplements and fortified foods combined, unless a clinician directs a different amount for a specific reason. Because supplements and fortified foods add up, check the total from every product you take.

Your clinician may recommend a different plan if any of these apply to you. These higher or adjusted amounts are chosen and prescribed by a clinician, so they should not be self-selected from over-the-counter products:

• A previous pregnancy affected by a neural tube defect, or a close family history of one. The CDC advises a much higher prescribed amount, 4,000 mcg per day, for people who have had a prior neural tube defect pregnancy, starting at least 1 month before conception and continuing as your clinician directs. Do not reach this amount by taking extra over-the-counter tablets on your own.
• Anti-seizure medicines. Some of these medicines are associated with a higher chance of birth defects. The AAN, AES and SMFM practice guideline on antiseizure medication in pregnancy reviews this evidence and addresses folic acid supplementation (Teratogenesis, Perinatal, and Neurodevelopmental Outcomes After In Utero Exposure to Antiseizure Medication). Do not stop or change a seizure medicine on your own. Seizures themselves can be dangerous in pregnancy. Ask your prescriber what folic acid amount fits your plan.
• Diabetes or a high body weight. These are associated with a higher chance of neural tube defects, so your clinician may decide whether a different amount is appropriate for you.
• Conditions that affect absorption, such as celiac disease or some bowel surgeries.
• Other medicines that interact with folate, such as methotrexate. Methotrexate carries a boxed warning, the strongest label warning, for pregnancy loss and birth defects, so tell your prescriber before you try to conceive or if you could be pregnant. Do not stop or change it on your own.

You may have read about MTHFR gene variants and special forms of folate. Variants are common, and whether testing or a special product adds anything in pregnancy is a question for your clinician. A single gene result does not by itself determine your plan.

Is more folic acid better? Limits and cautions

More is not necessarily better. Higher amounts are used in specific situations under a clinician's direction, not as a general upgrade. MedlinePlus (NIH) on vitamins notes that vitamins and supplements can affect health in ways that depend on the amount taken and your other medicines, so it is worth reviewing the full list with a professional.

One known concern is that folic acid can correct the type of anemia caused by low vitamin B12 while the B12 deficiency continues. The nerve effects of low B12 can then go unnoticed. If you have symptoms such as numbness or tingling in the hands or feet, memory trouble, a sore tongue, or unusual tiredness, tell your clinician. A blood test can help sort out the cause. Plant-based eaters and people who have had certain stomach or bowel surgeries may be at higher risk of low B12.

Folic acid is not a replacement for other prenatal care. Iron, calcium, vitamin D and other nutrients are discussed in their own articles, including our guide to how much iron you need during pregnancy. Some prenatal vitamins contain iron, which can be dangerous to children who swallow them.

Keeping supplements safe at home

Prenatal vitamins can look like candy, especially gummies and chewable tablets. Iron-containing products are a recognized poisoning risk for young children. Store them out of reach and in child-resistant containers. If a child swallows a prenatal vitamin or any supplement containing iron, call Poison Control at 1-800-222-1222 right away. If the child is unresponsive, having trouble breathing or having a seizure, call 911.

Other things that affect neural tube risk

Folic acid is one piece of a larger picture. Other factors associated with neural tube defects include some medicines, poorly controlled diabetes, fever early in pregnancy, and a prior affected pregnancy. MedlinePlus (NIH) on pregnancy and medicines explains that some medicines can affect a developing baby and that you should discuss all of them, including over-the-counter products and supplements, with your clinician. If you are on a long-term medicine, a preconception visit gives time to review it. Do not stop a prescription on your own. Our articles on antidepressants in pregnancy and on which medications are safe in pregnancy cover those questions in more detail.

Fever in early pregnancy is worth mentioning to your clinician, who can advise on treatment. Do not assume it is harmless, and do not treat it with a medicine before checking that it is appropriate in pregnancy.

What to ask at a preconception or first prenatal visit

• Which amount of folic acid fits my history, and should I start now?
• Do my current medicines, including any for seizures, diabetes, arthritis or psoriasis, change that plan?
• Is my prenatal vitamin a good match, and does it contain iron I should account for?
• Should I have bloodwork, such as a vitamin B12 level, based on my diet or health conditions?
• What screening for neural tube defects is available during pregnancy, such as ultrasound and blood tests?

Bring the actual bottles or photos of the labels. Brand names can hide the real contents, and clinicians can only judge the total if they can see it. For more on the general course of care, see MedlinePlus (NIH) on pregnancy.

Side effects and when a supplement may be causing a problem

Folic acid is generally well tolerated at usual amounts. Prenatal vitamins as a whole can cause nausea, constipation or an upset stomach, often because of the iron rather than the folic acid. Taking the vitamin with food, or at a different time of day, may help some people. Ask your pharmacist or prescriber before changing how a prescribed product is taken.

A true allergy to a folic acid tablet is uncommon. Hives, swelling of the face, lips or throat, wheezing, or trouble breathing after a dose need emergency care. Mild rash or itching without breathing trouble should be reported to your clinician the same day.

When symptoms need urgent attention

See the emergency list below this article for symptoms that need 911 and those that need same-day care. Our article on spotting during pregnancy covers lighter bleeding. If you ever have thoughts of harming yourself, call or text 988, the Suicide and Crisis Lifeline.

When to Seek Medical Care