Prenatal vitamins: Why they’re so important

Are prenatal vitamins really necessary? Yes. It’s hard to get all the nutrients you and…

Prenatal vitamins: Why they’re so important

Are prenatal vitamins really necessary?

Yes. It’s hard to get all the nutrients you and your baby need, even if you eat a wide variety of food, including meat, dairy products, fruits, vegetables, grains, and legumes.

Most women can benefit from taking a prenatal vitamin and mineral supplement (preferably before trying to conceive). Think of it as an insurance policy to make sure you’re getting the right amount of certain crucial nutrients during pregnancy.

Taking a prenatal vitamin is even more important for women with dietary restrictions, health issues, or pregnancy complications. This includes women who:

  • Are vegetarians or vegans
  • Are lactose intolerant or have other food intolerances
  • Smoke or abuse other substances
  • Have certain blood disorders
  • Have an eating disorder
  • Have certain chronic diseases
  • Have had gastric bypass surgery
  • Are having twins or higher multiples

What’s in a prenatal supplement that I can’t get from food?

Two crucial nutrients – folic acid and iron – are almost always included in prenatal vitamins because most pregnant women don’t get enough of them from food alone.

Folic acid

Getting enough of this B vitamin in the month before you conceive and very early in your pregnancy can reduce your baby’s risk of neural tube defects, such as spina bifida and anencephaly, by up to 70 percent. Folic acid may also reduce the risk of other defects, such as cleft lip, cleft palate, and certain heart defects. Taking folic acid may even lower your risk of preeclampsia.

Your body absorbs the synthetic version of folic acid better than the natural one found in food, so even if you eat a balanced diet, a supplement is strongly recommended.

For more details, see our complete article on folic acid in your pregnancy diet.


Most moms-to-be don’t get enough of this mineral from their diet to meet their body’s increased need during pregnancy, and this can lead to iron-deficiency anemia. Preventing iron-deficiency anemia can cut your risk of preterm delivery, low birth weight, and infant mortality.

For more details, see our complete article on iron in your pregnancy diet.

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What nutrients do I need that may not be in a prenatal supplement?


Your prenatal vitamin may contain calcium, but there’s a chance it won’t be enough. You need calcium to help your baby grow strong bones and teeth as well as healthy nerves and muscles (including the heart).

Most prenatal vitamins contain between 100 and 200 milligrams (mg) of calcium, but some don’t contain any. That’s because calcium is a particularly bulky mineral, and the pills are already big enough!

To find out how much calcium you need and how to get it, see our complete article on calcium in your pregnancy diet.

Essential fatty acids

Prenatal vitamins don’t contain any essential fatty acids, such as the omega-3 fatty acids DHA and EPA, which are important for the development of your baby’s brain, nerve, and eye tissue.

Fish is a major source of DHA and EPA, but you have to be careful about not eating too much fish that’s high in mercury while you’re pregnant.

Because omega-3s are so important for your baby, it’s a good idea to talk with your healthcare practitioner about whether you need a supplement.

Learn more:

Dietary fats in your pregnancy diet

Eating fish during pregnancy

Taking fish oil supplements during pregnancy

Vitamin D

Your body needs this fat-soluble vitamin to help build your baby’s bones and teeth. Vitamin D plays an important role in maintaining levels of calcium and phosphorus.

If you’re lacking vitamin D during pregnancy, your baby may be short on the vitamin at birth. This can put your child at risk for rickets (which can lead to fractures and deformity), abnormal bone growth, and delayed physical development. A deficiency of vitamin D has also been linked to a greater risk of developing pregnancy complications such as preeclampsia and gestational diabetes, but more research is needed to confirm these links.

To find out how much vitamin D you need and how to get it, see our complete article on vitamin D in your pregnancy diet.

When should I start taking prenatal vitamins?

Take a prenatal vitamin every day as soon as you realize you’re pregnant.

Because folic acid is so important in the earliest weeks of your pregnancy, ideally you would start taking prenatal vitamins before you conceive – that’s why many doctors recommend them for women who might become pregnant.

Taking prenatal vitamins for at least three months before you conceive also could lessen morning sickness once you’re pregnant. And if you breastfeed your baby, your doctor might recommend you continue taking prenatal vitamins even after your baby is born.

How do I choose a prenatal supplement that’s right for me?

Unfortunately, no standards have been set for what should be in vitamin and mineral supplements because the Food and Drug Administration doesn’t regulate them. That means it’s up to you and your healthcare practitioner to make sure you choose one that’s safe and appropriate for you. (See our article on buying supplements for more guidance.) 

At your first prenatal checkup or at a preconception visit, your practitioner will probably prescribe a daily vitamin or recommend an over-the-counter brand. A good supplement provides certain nutrients (such as folic acid and iron) that you may not be able to get enough of from your diet. But it also provides no more than the recommended amounts of other nutrients that can be harmful to your baby if you take too much – like vitamin A.

Vitamin A derived from animal products can cause birth defects when taken in high doses. That’s why the vitamin A in most prenatal vitamins is at least partly in the form of beta-carotene.

Beta-carotene is a nutrient found in fruits and vegetables, and your body converts this type to vitamin A. Unlike vitamin A from animal products, beta-carotene is considered safe even in high doses.

Note: Make sure you don’t take any other vitamin or mineral supplements while you’re taking a prenatal supplement unless your practitioner recommends it.

What if I mistakenly take two prenatal vitamins on the same day?

Don’t worry. Taking twice the recommended amounts of these nutrients on just one day won’t harm you or your baby. But taking a double dose more often can be harmful, so it’s important not to do it regularly.

If your practitioner says you need more of a certain nutrient than your prenatal vitamin provides, take the additional amount as a separate supplement.

What if I have trouble swallowing the pills?

Prenatal vitamin and mineral supplements tend to be pretty big. They can be hard to swallow, especially if you’re dealing with nausea.

If this is a problem for you, your practitioner may be able to recommend a smaller pill or one with a slick coating that makes it easier to get down. (Pills that don’t contain calcium tend to be smaller, and you can get your calcium in other ways.)

Chewable prenatal vitamins are also available. There’s even a powdered pregnancy supplement that you mix with water. So if you don’t like one version, keep trying different options until you find a prenatal supplement you can take.

What if the vitamins upset my stomach?

If you’re taking a supplement with more than the recommended 30 mg of iron, it may upset your gastrointestinal tract. (Supplements that contain 30 mg or less probably won’t cause you any problems.)

To avoid queasiness, try taking your supplement at bedtime or with a meal to make it easier to tolerate.

Taking a lot of iron can lead to constipation, which is already a problem for many pregnant women. It can also cause nausea or, more rarely, diarrhea.

If iron upsets your stomach, talk to your healthcare practitioner about it. If you’re not anemic, it may make sense for you to switch to a prenatal vitamin with less iron. Otherwise, try to ease constipation by:

  • Drinking prune juice
  • Eating two to three servings of fruit a day
  • Taking a psyllium fiber supplement