Multiple vitamin supplements taken during pregnancy may not be any more effective than folic acid-iron supplements in reducing the risk of low-birth-weight babies, according to the results of a study by researchers with the Johns Hopkins Bloomberg School of Public Health's Center for Human Nutrition.

The study, conducted in rural Nepal, is published in the March 15 issue of the British Medical Journal.

Worldwide, 250 million low-birth-weight babies are born each year, 90 percent of them in developing countries where maternal micronutrient deficiencies are widespread. "Our research work is aimed at trying to discern the right combinations of micronutrients that will maximize the health benefits to both mother and child," explained Parul Christian, principal investigator of the study and associate research professor with the Center for Human Nutrition and the Department of International Health. "You have to consider the potential for negative interactions between micronutrients. Our study shows that more nutrients are not necessarily better," he said.

For the study, CHN researchers gave 4,926 pregnant Nepalese women one of four daily supplements: folic acid; folic acid-iron; folic acid-iron-zinc; or a multiple micronutrient supplement containing folic acid, iron and zinc and 11 other micronutrients. All participants received vitamin A, with a control group receiving vitamin A alone. Previous studies by CHN researchers showed that vitamin A reduces pregnancy-related deaths in Nepal.

The findings showed that supplementation with folic-acid iron reduced the incidence of low birth weight by 16 percent, and the multiple micronutrient supplements reduced low birth weight by 14 percent. Folic acid-iron-zinc supplementation and folic acid supplementation alone had no significant effect on birth size.

Christian said the study provides important new information in the pursuit of a universal antenatal supplement in both the developing world and in disadvantaged populations in the United States. "Micronutrient deficiencies during pregnancy may predispose mothers to losing their fetuses, having low-birth-weight newborns or infants who grow poorly. In rural Nepal alone, where more than 40 percent of babies are born with low birth weight, a widespread micronutrient supplementation program could have a tremendous impact on the health and survival of millions of children," she explained.

While researchers are optimistic that they are making progress, Christian said more work is needed to understand the health effects of antenatal micronutrient use among mothers before it is widely adopted in the developing world.