Folic acid is the best choice for a healthy pregnancy

By Jessie Seiler

Updated: December 11, 2025

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15 min

When you’re pregnant, you’re going to do everything you can to give your baby the best start possible. That’s why it’s so frustrating when influencers and companies sell you lies about folic acid… and then try to sell you supplements that they claim are better. So how do we know that folic acid is important? Are we sure that it doesn’t cause cancer, autism, or depression? What about that tricky MTHFR gene variant? Here’s what you need to know to make a good decision about folic acid for you and your baby.

Folate and folic acid 101

Folate, or vitamin B9, is found in many foods, including dark green leafy vegetables, asparagus, brussels sprouts, oranges, walnuts, and beans.

Although you might hear folate and folic acid used interchangeably, they’re not exactly the same. Folate is an umbrella term that describes all forms of vitamin B9, and people often use it to refer to the version found in food. Folic acid refers to a synthetic, stable form of folate that is used in supplements or added to food. It’s also the form that’s been studied most thoroughly, precisely because it’s stable. (That means it can stand up to heat and light exposure. It even remains stable through cooking and baking.)

Whether we’re talking about folate or folic acid, the vitamin plays a key role in how cells grow and divide. “Our cells turn over all the time,” says Marian Neuhouser, a nutritional epidemiologist and leader of the Cancer Prevention Program at the Fred Hutchinson Cancer Center in Seattle. And replacing them requires DNA, the genetic instructions for your body. “[Folate] helps make precursors for DNA synthesis,” explains Neuhouser. That’s why it’s especially important for anyone who is pregnant or can become pregnant.

Why folic acid is critical during pregnancy

During pregnancy, the body needs more folate than usual. In the early stages, “those cells are replicating really fast in the embryo, and you need the precursors for DNA to make the cells,” says Neuhouser. The consequences of insufficient folic acid during pregnancy are serious. In the first 28 days after conception, the vitamin helps to form the neural tube, which becomes the baby’s brain and spine. If it doesn’t form correctly, the baby may be born with a neural tube defect like spina bifida (when the neural tube doesn’t close all the way, leading to incomplete formation of the spinal cord) or more-serious anencephaly (when the top of the neural tube doesn’t close, resulting in parts of the brain not forming and, in almost all cases, miscarriage or death shortly after birth).

In the 1960s, researchers noticed a link between low blood levels of folate in the birthing parent and babies born with neural tube defects. But those studies couldn’t prove that low folate levels caused the defects. (Something else about the parents or babies might have explained the results.)

But since those initial findings, results from randomized controlled trials have conclusively established that taking folic acid supplements early in pregnancy reduces the risk of neural tube defects. In one of those trials—it recruited 1,817 people who had previously given birth to a child with a neural tube defect, so they had a high risk of a second pregnancy with the same result—folic acid reduced the risk by 72 percent. In fact, the trial was so successful that it was halted early because the outcome was already clear and continuing would not have been fair for the people who weren’t receiving folic acid.

In 1992, the United States Public Health Service recommended that anyone capable of becoming pregnant should consume 400 micrograms of folic acid every day (in addition to the folate they were getting from food) to prevent neural tube defects, whether or not they were planning a pregnancy. That’s because many people don’t find out that they are pregnant until at least a month after conception, and roughly 40 percent of pregnancies are unplanned. That recommendation, which is still in place today (though it currently stands at 400 to 800 micrograms a day), has been echoed by the American College of Obstetricians and Gynecologists, American Academy of Family Physicians, and American Academy of Pediatrics.

Why are those recommendations specifically for folic acid, and not more broadly for folate? Because the randomized trials used folic acid. Folate will probably never be tested. “This is a case where a trial is not always the most ethical choice,” says Neuhouser. Why? The evidence that folic acid prevents neural tube defects is so solid that it would be unethical to assign pregnant people to take a placebo or folate. 

Folic acid fortification in the United States 

Efforts to prevent neural tube defects didn’t stop with the 1992 recommendation for anyone who can become pregnant to take folic acid. In 1998, the FDA required companies to add folic acid to all “enriched” grains, including any bread, pasta, rice, cereal, flour, or other grain product that’s marketed as “enriched.” (“Enriched” grains were already being fortified with iron and three other B vitamins: thiamin, riboflavin, and niacin.) The results were conclusive: Folic acid fortification has prevented an estimated 1,300 neural tube defects every year. 

How much folate do I need? Should I take a supplement?

How much folate you need—and whether you’ll need a supplement to get there—depends on your age and whether you’re pregnant or could become pregnant.

In the tables below, you’ll see the term “DFE.” It stands for “dietary folate equivalents,” which reflects the fact that your body absorbs folic acid more readily than folate, so you need less folic acid than folate to hit your daily targets. For example, 240 micrograms of folic acid and 400 mcg of folate are both equal to 400 mcg DFE. (To convert from micrograms of folic acid to micrograms of DFE, multiply by 1.7.)