Prenatal vitamins fill specific nutritional gaps that develop during pregnancy, protecting both the mother and the developing baby. They supply higher doses of nutrients like folic acid, iron, and iodine that are difficult to get from food alone, especially when pregnancy increases your body’s demand by 50% or more for certain vitamins and minerals. The benefits start before conception and continue through delivery.
Preventing Neural Tube Defects
The single most important nutrient in a prenatal vitamin is folic acid, a B vitamin that helps form the baby’s brain and spinal cord during the earliest weeks of pregnancy. Getting 400 micrograms of folic acid daily reduces the risk of neural tube defects like spina bifida by roughly 50%, according to CDC estimates. These defects develop within the first 28 days after conception, often before you even know you’re pregnant, which is why the timing of supplementation matters so much.
The recommended intake for pregnant women is 600 micrograms of dietary folate equivalents per day. If you’ve had a previous pregnancy affected by a neural tube defect, the recommendation jumps to 4,000 micrograms daily, starting at least a month before conception and continuing through the first trimester.
When to Start Taking Them
Ideally, you’ll start taking a prenatal vitamin at least three months before you become pregnant. That lead time allows your body to build up adequate stores of folic acid and other nutrients before the critical early weeks of fetal development. Since nearly half of pregnancies are unplanned, many health organizations recommend that all women of childbearing age who could become pregnant take 400 micrograms of folic acid daily, whether or not they’re actively trying to conceive.
Supporting Your Blood Supply
During pregnancy, the volume of blood in your body increases significantly, and your body needs extra iron to produce the additional hemoglobin (the protein in red blood cells that carries oxygen). You need 27 milligrams of iron per day while pregnant, nearly double what’s recommended outside of pregnancy. Without enough iron, you’re at risk for iron deficiency anemia, which causes fatigue, weakness, and can affect how well oxygen reaches your baby.
Most prenatal vitamins contain iron specifically to prevent this. The American College of Obstetricians and Gynecologists recommends low-dose iron supplementation starting in the first trimester.
Building the Baby’s Brain and Nervous System
Several nutrients in prenatal vitamins work together to support fetal brain development, but two stand out beyond folic acid: iodine and choline.
Iodine is a trace mineral your thyroid gland uses to produce hormones that regulate brain, bone, and organ development in the fetus. Severe iodine deficiency can cause lifelong developmental delays and intellectual disability. Pregnant women need 220 micrograms of iodine per day, and the American Thyroid Association recommends supplementing with 150 micrograms daily, ideally starting three months before conception. Not all prenatal vitamins include iodine, so it’s worth checking the label.
Choline plays a role in memory, attention, and learning. Research reviewing multiple human studies found that higher maternal choline intake during the second half of pregnancy (450 mg or more per day) was associated with better cognitive outcomes in children. The adequate intake during pregnancy is 450 mg per day. Like iodine, choline is frequently left out of prenatal formulas, so you may need to get it through foods like eggs, liver, and soybeans, or a separate supplement.
Developing Healthy Bones
Vitamin D helps your body absorb calcium from food, which is essential for normal bone mineralization and growth in the fetus. If you don’t get enough calcium, your body will pull it from your own bones to supply the baby. Pregnant women need 1,000 mg of calcium daily (1,300 mg for those under 19) and 600 international units of vitamin D per day.
Most prenatal vitamins contain about 400 international units of vitamin D per tablet, which falls slightly short of the recommendation. If you have limited sun exposure or darker skin, you may need additional vitamin D. Calcium is another nutrient that’s often present in lower amounts in prenatals, particularly gummy versions, because the mineral itself is bulky and hard to compress into a single pill.
Supporting Eye and Brain Maturation With DHA
DHA, an omega-3 fatty acid found in fish oil, is a structural building block of the baby’s brain and retinas. A large study across three European countries found that higher DHA levels in cord blood at delivery were associated with better neurological outcomes in children at age 5.5. The supplementation used in that trial was 500 mg of DHA per day starting at week 20 of pregnancy.
Standard prenatal tablets don’t always include DHA, so many brands sell it as a separate softgel. If you eat two or more servings of low-mercury fish per week, you may already be getting enough, but a supplement can help fill the gap if fish isn’t a regular part of your diet.
What Else Is in the Formula
Beyond the headliners, prenatal vitamins typically include a range of supporting nutrients, each with a specific job during pregnancy:
- Vitamin B6 (1.9 mg/day): Supports the baby’s brain and nervous system development. It also helps some women manage nausea in early pregnancy.
- Vitamin B12 (2.6 mcg/day): Works alongside folic acid to form red blood cells and support nervous system development. Especially important if you follow a vegetarian or vegan diet.
- Zinc (11 mg/day): Involved in cell division and immune function, both of which ramp up during pregnancy.
- Vitamin A (770 mcg/day): Supports fetal eye, skin, and immune system development. Preformed vitamin A has an upper limit of 3,000 mcg because excessive amounts can cause birth defects.
Gummy vs. Tablet Prenatals
Gummy prenatal vitamins are easier on the stomach, which makes them appealing during the first trimester when nausea is common. The trade-off is that gummies frequently contain less iron and calcium than tablets, and some contain none at all. Iron is difficult to include in gummy form because of its metallic taste, and calcium takes up too much physical space. If you prefer gummies, check whether you’ll need to supplement iron and calcium separately, especially if your diet doesn’t reliably provide them.
Dealing With Side Effects
The most common complaints about prenatal vitamins are nausea and constipation, and iron is usually the culprit. Taking your prenatal with food or right before bed can reduce nausea. If constipation is the issue, drinking more water, eating high-fiber foods, and staying physically active all help. Switching to a prenatal with a lower iron dose or a different form of iron (like iron bisglycinate, which is gentler on the stomach) is another option worth discussing with your provider. Some women find that splitting the dose, if their prenatal allows it, makes the side effects more manageable.