Do Prenatal Vitamins Do More Harm Than Good?

I thought you were a bad mother if you didn't take prenatal vitamins. According to my doctor, that's not true. And he's not alone.

When I asked my OB what I should do about prenatal vitamins—those revered nutritional supplements—he shocked me by reaching under his desk and pulling out the garbage can.

"Put them in here," he said.

My doctor's advice made my jaw drop.

On one hand, that was a huge relief, as the hyperemesis gravidarum (extreme morning sickness) that characterized all my pregnancies prevented me from swallowing almost any pill.

But I thought you were a bad mother if you didn't take prenatal vitamins. In fact, before I became so ill, I purchased a jug of prenatal vitamins that included every possible herb that might benefit my brand new embryo. Because you're better safe than sorry, right? Shouldn't everyone take a multivitamin?

According to my doctor, that's not right. And he's not alone. In February, a study published in Archives of Internal Medicine showed that daily multivitamin use doesnt ward off cancer or heart disease, even though a nutrient-rich diet does.

Charles Lockwood, MD, the chief of obstetrics and gynecology at Yale–New Haven Hospital, confirmed my doctor's advice: "If you eat a balanced diet and are not iron deficient, it is not clear that prenatal vitamins result in any health benefits during pregnancy."

My doctor then referred me to Williams Obstetrics, the essential source of information for ob-gyns. In the 17th edition, I discovered this passage:

"The practice of supplying vitamin supplements prenatally is a deeply ingrained habit of many obstetricians, even though scientific evidence to show that the usual vitamin supplements are of benefit to either the mother or her fetus is quite meager."

Why doesn't anyone know this? I read on to discover the Committee on Maternal Nutrition of the National Research Council pointed out that pregnancy supplements are of doubtful value, "except for iron and possibly folic acid."

So we're not completely off the hook—we still benefit from popping a few pills. But which pills, and how much? That seems to be quite a topic of debate. What does seem certain is that we're better off taking our vitamins more discriminatingly, if we take them at all.

For example, if we take large doses of vitamin C, we could give our unborn babies scurvy, according to William Obstetrics. And supplementing iodine beyond our usual salt intake can "induce a sizeable goiter in the fetus." Yikes!

I learned that the pills I should take while pregnant include the iron and folic acid mentioned in Williams Obstetrics, as well as the new darling of nutritional experts, vitamin D.

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Erica Kain
Last Updated: September 24, 2009

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