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Regular multivitamin use near time of conception significantly reduces preeclampsia risk

July 27, 2006

Women who are considering becoming pregnant may significantly reduce their risk of developing a common life-threatening complication called preeclampsia by taking a multivitamin supplement regularly three months before conception and during the first trimester of pregnancy. This finding is being reported in a University of Pittsburgh study available online now through an "advance access" feature of the American Journal of Epidemiology. The paper is scheduled for publication in the Sept. 1 print issue of the journal.

Overall, women who used multivitamins regularly showed a 45 percent reduction in preeclampsia risk, according to the study. However, results were even more remarkable for women who were not overweight prior to pregnancy.

"Our data show that women who are not overweight before pregnancy and who used multivitamins at least once a week before conception and in the first three months of pregnancy reduced their risk of preeclampsia by a striking 72 percent compared to those who didn't take a multivitamin during this time period," said Lisa Bodnar, Ph.D., M.P.H., R.D., assistant professor of epidemiology at the University of Pittsburgh Graduate School of Public Health (GSPH). "At this time, multivitamin use makes little apparent difference in preeclampsia rates for women who are overweight before pregnancy. Even so, the results suggest that regular multivitamin use in the pre-pregnancy period may help to prevent preeclampsia."

Also known as toxemia, preeclampsia affects about 7 percent of first pregnancies and is a leading cause of premature delivery and maternal and fetal death. Signs of preeclampsia include high blood pressure, protein in the urine and swelling of the hands and feet. Untreated, the condition may progress to the far more serious eclampsia, which can lead to seizures, coma and death.

Preeclampsia is more prevalent in the developing world, where it accounts for up to 80 percent of maternal deaths. And while treatment is more readily available in developed countries, preeclampsia remains the leading cause of maternal death. Infants born to mothers with preeclampsia have a risk of mortality five times greater than those born to women with normal pregnancies. In the United States alone, nearly 15 percent of preterm deliveries are a result of preeclampsia.

Dr. Bodnar and her colleagues evaluated data from 1,835 women who were enrolled in the University of Pittsburgh's Pregnancy Exposures and Preeclampsia Prevention Study between 1997 and 2001. Overall, the prevalence of preeclampsia was 4.4 percent for non-multivitamin users and 3.8 percent for those who used multivitamins, with the most significant differences being noted among women who had a body mass index (a common body weight measure) of less than 25. Most authorities define overweight at a BMI of 25 and obesity as a BMI of 30 or above.

Because multivitamins contain many nutrients, it is difficult to know the exact mechanism by which the risk of preeclampsia is reduced, noted Dr. Bodnar, who also is an assistant investigator at the university-affiliated Magee-Womens Research Institute (MWRI). Other recent studies have shown limited benefits - and some risk - associated with large doses of vitamins C and E in women at high risk of preeclampsia. "However, the study does show further evidence that nutrition is relevant for the prevention of preeclampsia," she said.

Although Dr. Bodnar and her colleagues tried to adjust for possible complicating factors such as smoking, exercise habits, fruit- and vegetable-intake, demographic and other socioeconomic factors, it is possible that the study findings could be attributed to other differences among multivitamin supplement users and nonusers that investigators did not identify. In addition, the analysis depended on self-reporting of multivitamin use rather than a random assignment of supplement use. Even so, the association between multivitamin use and diminished risk of preeclampsia strongly continues inasmuch as adjustments are possible.

"Preeclampsia is a potentially devastating condition for mother and baby," observed James M. Roberts, M.D., director of the Magee-Womens Research Institute and senior author of the paper. "It may be that taking a multivitamin prior to conception positively influences embryonic implantation, which is a physiologic process known to be abnormal in preeclampsia. More study is needed to clarify these findings."

Researchers are unsure of the reasons why multivitamin use appears to have no benefit to preeclampsia risk in overweight women, Dr. Bodnar said. "It may be that typical multivitamins, which contain low nutrient doses, may not be adequate to overcome the metabolic challenges associated with the development of preeclampsia along with being overweight and pregnant," she added. "But again, more study is needed to test these ideas."

University of Pittsburgh Medical Center