Too Many A's?

Prenatal vitamins may deliver more than baby needs.

When a woman becomes pregnant, one of her doctor’s first actions is to prescribe prenatal vitamin supplements to stimulate the healthy development of her baby. But could those supplements be delivering too much of a good thing?

Nutritional scientist Sherry Tanumihardjo worries this may be the case for vitamin A, a compound commonly included in prenatal supplement formulas and vitamin-fortified foods. While important to fetal development and healthy lactation in breast-feeding mothers, vitamin A can become toxic in higher doses—and there’s little data about how much of it is enough for a developing fetus.

“The high intake of vitamin A from supplements and fortified foods worldwide has caused us to be concerned,” says Tanumihardjo.

With colleagues at the Wisconsin Regional Primate Research Center, Tanumihardjo is trying to establish the proper balance. In one recent study, her team found that when pregnant monkeys consumed foods fortified with vitamin A, higher levels of the vitamin showed up in their fetuses’ livers during early gestational stages, a sign that they were passing on more of the substance than their babies can handle.

While developing monkeys store the excess vitamin A in a benign form that seems to protect them from harmful effects, researchers aren’t yet sure that humans have the same defenses. And even if they do, Tanumihardjo says future research may point to a better formula for prenatal supplements that ensures mother and baby get just what they need—and not more.