Most women can stop taking a standalone folic acid supplement after 12 weeks of pregnancy. The World Health Organization recommends 400 micrograms (mcg) of folic acid daily from the time you start trying to conceive through the end of the first trimester. After that point, the nutrient’s most critical job is done, though your body’s need for folate doesn’t disappear entirely.
Why 12 Weeks Is the Cutoff
Folic acid’s primary role in early pregnancy is preventing neural tube defects, which are serious birth defects of the brain and spine. The neural tube, the structure that eventually becomes your baby’s brain and spinal cord, folds and closes during the third and fourth weeks of pregnancy. That’s often before many women even know they’re pregnant, which is why the CDC recommends all women capable of becoming pregnant take 400 mcg daily as a baseline.
By the end of the first trimester (around 12 weeks), the neural tube has long since closed. The window where folic acid provides its most protective benefit has passed. This is why guidelines from both the WHO and major medical bodies set 12 weeks of gestation as the point where dedicated folic acid supplementation is no longer necessary for most pregnancies.
High-Risk Pregnancies Have a Different Timeline
Some women are prescribed a much higher dose of folic acid, typically 5 milligrams (5,000 mcg) per day, which is more than ten times the standard amount. This higher dose applies to women with specific risk factors for neural tube defects. The recommendation for these women is to start taking 5 mg daily at least two months before conception and continue through the end of the first trimester.
Risk factors that may warrant this higher dose include:
- Previous pregnancy affected by a neural tube defect
- Diabetes (pre-existing, not gestational)
- Obesity with a BMI over 35
- Malabsorption conditions like inflammatory bowel disease
- Certain medications that interfere with how your body processes folate, including some anti-seizure drugs and methotrexate
- Smoking
- Genetic variations that affect folate metabolism (such as MTHFR polymorphisms)
If you fall into any of these categories, the timing and dosage should be guided by your provider. Even for high-risk women, though, the supplementation window typically ends after the first trimester.
You Still Need Folate After the First Trimester
Stopping a standalone folic acid supplement at 12 weeks doesn’t mean your body stops needing folate. The recommended daily intake of folate during pregnancy is 600 mcg of dietary folate equivalents, up from 400 mcg for non-pregnant women. This higher need lasts through the entire pregnancy because folate supports DNA synthesis, red blood cell production, and placental growth.
Most prenatal vitamins contain between 400 and 800 mcg of folic acid alongside iron, calcium, vitamin D, and other nutrients your body needs in higher amounts during pregnancy. If you’ve been taking a standalone folic acid pill on top of a prenatal, the 12-week mark is typically when you drop the standalone supplement and continue with just the prenatal. If your prenatal already contains folic acid (most do), you’re covered without any additional supplementation.
Food also contributes. Leafy greens, lentils, chickpeas, fortified cereals, and citrus fruits are all solid sources. In the U.S., most enriched grain products like bread and pasta are fortified with folic acid by law, so many women get a meaningful amount through their regular diet without realizing it.
Can Too Much Folic Acid Be a Problem?
There is some evidence that very high folic acid intake later in pregnancy may not be entirely harmless. A dose-response meta-analysis published in Frontiers in Pediatrics found that maternal folate intake of 581 mcg per day or more was associated with a slightly increased risk of childhood asthma. Supplementation in the third trimester specifically showed a modest but statistically significant correlation. Below that 581 mcg threshold, no increased risk was observed.
This doesn’t mean folic acid causes asthma, and the effect sizes were small. But it does suggest there’s no benefit to megadosing on folic acid throughout pregnancy “just in case.” The standard amount found in a prenatal vitamin, combined with a reasonably balanced diet, is enough to meet your needs without pushing intake to levels where potential downsides start to appear.
Possible Benefits of Continuing Into the Second Trimester
One area of ongoing interest is whether folic acid in the second trimester may help reduce the risk of preeclampsia, a dangerous pregnancy complication involving high blood pressure. A study of nearly 3,000 pregnant women found that multivitamin supplementation containing folic acid in the early second trimester was associated with a 63% reduction in preeclampsia risk. The supplementation also raised serum folate levels and lowered homocysteine, an amino acid linked to vascular problems when elevated.
This is worth noting, but it doesn’t change the core recommendation. Most women who continue taking a prenatal vitamin through their pregnancy are already getting folic acid during the second trimester. The takeaway isn’t to add extra folic acid, but rather that staying on your prenatal vitamin consistently matters beyond just the first 12 weeks.
The Practical Takeaway
For a standard-risk pregnancy, the timeline looks like this: start taking 400 mcg of folic acid daily before you conceive (ideally at least one month before, though earlier is better), continue through 12 weeks of pregnancy, and then transition to relying on your prenatal vitamin and diet for folate needs. If you’ve been taking a prenatal vitamin from the start that already contains folic acid, there’s no separate supplement to stop. You simply keep taking the prenatal.
If you’re on a high-dose prescription of 5 mg per day, the same 12-week endpoint generally applies, but confirm the plan with your provider since your risk profile may warrant a more individualized approach.