Prenatal Supplements

What are prenatal supplements?

Prenatal supplements are vitamins designed especially for pregnant women. Most of them contain more folic acid and iron than you’ll find in a standard adult multivitamin. Pregnant women need more of these nutrients than usual — specifically, they need 200 micrograms (mcg) a day more of folic acid and close to 50 percent more iron daily to make more blood to nourish the fetus. Women also need 1,000 milligrams (mg) of calcium a day to prevent bone loss late in pregnancy, so prenatal vitamins usually contain this vital mineral as well.

Ideally, you should start taking the vitamins before you get pregnant. Neural tube defects such as spina bifida can develop in an embryo before a woman even knows she’s pregnant. That’s why doctors encourage women who are trying to conceive to start taking prenatal supplements, or at least folic acid. Taking folic acid, a B vitamin also known as folate, both before and during pregnancy dramatically reduces the chance that your baby will be born with spina bifida or other neural tube defects.

Every woman of childbearing age should take 400 micrograms (mcg) of folic acid a day. Most prenatal vitamins contain twice that amount (800 mcg), the level recommended by the U.S. Food and Drug Administration. (The FDA recommends taking no more than 1,000 mcg per day, unless you have previously had a baby with a brain or spine defect or if someone in the family has spina bifida. In these cases your doctor may prescribe 4,000 micrograms a day — 10 times the normal dose in an effort to prevent other birth defects.

Should I take prenatal supplements?

Most pregnant women really do need to take a prenatal supplement. The Institute of Medicine has concluded that pregnant women should be able to get all of their nutrients except for iron from their diet alone, but in reality many women fall short of their goals. With today’s busy lifestyles, it can be difficult to get enough vitamins and minerals from your diet, and a supplement is an easy form of “insurance.”

Before you start taking any supplement, consult your doctor to ensure it won’t do more harm than good and won’t interact with other medications you may be taking. If you’re expecting twins, for example, you may need a special type with different amounts of certain nutrients. Doctors will also typically check to see whether iron deficiency is a problem through blood tests in your initial visit and again when you are about two thirds of the way through pregnancy. These blood tests can help you know whether or not you need to take iron supplements as your pregnancy continues into the third trimester.

Once you and your doctor decide which supplement is best for you, read the directions before you start taking them; some brands require you to take up to six pills per day.

If I take a supplement, do I still have to pay attention to my diet?

Definitely. Keep in mind that taking a supplement isn’t a guarantee you’ll be getting everything you need. In fact, most prenatal supplements only have 15 to 25 percent of the daily value of calcium, and you still need to make up the difference with food rich in the mineral, such as milk, yogurt, broccoli, lentils, and spinach — or by taking additional calcium.

The bottom-line is that supplements aren’t an efficient way to get major nutrients, and you shouldn’t rely on them to replace balanced meals. Try to avoid junk food, and eat at least five to six cups of fruits and vegetables a day and as many whole grain foods as possible.

What’s in the supplements?

Prenatal supplements vary widely from brand to brand. Besides iron, calcium, and folic acid, they often contain:

  • Vitamins A, C, D, and E (prenatal vitamins generally contain 3,000 to 5,000 IU of vitamin A, which women can supplement with food). More than 10,000 IU of preformed vitamin A (retinol and retinyl esters) can be harmful to a developing fetus, so be sure to check the label. The FDA recommends that pregnant women get their vitamin A in the form of beta-carotene, which is found in fruits and vegetables as well as many supplements and is not considered toxic.
  • Other B vitamins including thiamine (B1), riboflavin (B2), pantothenic acid (B5), B6, and niacin (B12)
  • Important minerals including copper, magnesium, selenium, and zinc.
    Certain forms of iron (including ferrous fumarate and ferrous gluconate) are less likely to cause upset stomach and nausea than the form most commonly used, ferrous sulfate. Slow-release iron pills cost a little more, and some women can tolerate them better than the regular kind.

You may also prefer to pay more for pills containing calcium citrate malate instead of calcium carbonate because they don’t need to be taken with meals. (This is best if your supplement has iron too). In addition, it’s far less likely to have toxic heavy metals such as lead, cadmium, or mercury than brands containing unrefined calcium from oyster shells, bone meal, or the mineral dolomite.

Some prenatal supplements sold at natural food stores even contain herbs such as ginger and red raspberry and probiotic bacteria such as lactobacillus. If you’re thinking of taking complex supplements like these, consult with your doctor first.

Does it matter how I take them?

Follow the directions on your particular bottle, but bear in mind that because all those nutrients are jostling each other in your stomach, you probably won’t get everything the label promises.

If you’re relying on your supplement for extra iron, you’ll probably want to take it between meals so more will get absorbed. Taking extra iron may cause constipation, so drink a lot of water throughout the day. Another thing to consider is that caffeine hinders iron and calcium absorption, so avoid having tea and coffee before or after you take your pill. Taking your pills with milk isn’t a great idea either because it interferes with iron and zinc absorption. Juice or water are best.

What if I can’t take a supplement?

If you’re having trouble keeping your pills down, try a different type. You can also try taking them at different times of the day, like in the afternoon or evening if you’re too queasy in the morning. There are even chewable tablets or liquid forms available if you can’t swallow large pills.

If these steps don’t help, consider taking smaller supplements tailored to your needs. Getting enough folic acid is most critical during the first trimester (to prevent birth defects), and iron is most important in the last two (to form additional blood). Calcium is important all through pregnancy — your bones store extra amounts early in pregnancy and divert it to your baby in the last trimester, when the skeleton develops. Ask your doctor for advice on how to get enough.

If you’re a vegetarian, it’s a good idea for you to consult a nutritionist for some personal advice.


Understanding Nutrition by Whitney and Rolfes (seventh edition). West Publishing Company, Minneapolis MN.

Institute of Medicine (Food and Nutrition Board) reports, published by the National Academy Press.

Dietary Reference Intakes for Calcium, Phosphorus, Magnesium, Vitamin D, and Fluoride.

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