Science & Technology/Pitt Study Links Low Vitamin D During Pregnancy to Preeclampsia

Issue Date: 
September 17, 2007


Vitamin D deficiency early in pregnancy is associated with a five-fold increased risk of preeclampsia, according to a Pitt study reported this month in the Journal of Clinical Endocrinology and Metabolism.

A serious complication of pregnancy marked by soaring blood pressure and swelling of the hands and feet, preeclampsia is the leading cause of premature delivery and maternal and fetal illness and death worldwide, conservatively projected to contribute to 76,000 deaths each year.
Preeclampsia, also known as toxemia, affects up to 7 percent of first pregnancies, and health care costs associated with preeclampsia are estimated at $7 billion a year in the United States alone, according to the Preeclampsia Foundation.

“Our results showed that maternal vitamin D deficiency early in pregnancy is a strong, independent risk factor for preeclampsia,” said Lisa M. Bodnar, an assistant professor of epidemiology in Pitt’s Graduate School of Public Health (GSPH) and lead author of the study. “Women who developed preeclampsia had vitamin D concentrations that were significantly lower early in pregnancy compared to women whose pregnancies were normal. And even though vitamin D deficiency was common in both groups, the deficiency was more prevalent among those who went on to develop preeclampsia.”

For this investigation, Bodnar and her colleagues evaluated data and banked blood samples taken from women and newborns between 1997 and 2001 at Magee-Womens Hospital of the University of Pittsburgh Medical Center (UPMC) and affiliated private obstetrician practices. Data were analyzed for 1,198 women enrolled in the Pregnancy Exposures and Preeclampsia Prevention Study, a prospective survey designed to examine factors that may predispose women to preeclampsia. Out of this group, 55 cases of preeclampsia and 220 controls were selected for further study.
Samples of maternal blood were taken prior to 22 weeks pregnancy and again just before delivery. Samples of newborn umbilical cord blood also were tested for 25 hydroxyvitamin D, an indicator of vitamin D status.

“Low vitamin D early in pregnancy was associated with a five-fold increase in the odds of preeclampsia,” said Bodnar, who also is an assistant investigator at the Pitt-affiliated Magee-Womens Research Institute (MWRI). “Data showed this increased risk persisted even after adjusting for other known risk factors such as race, ethnicity, and prepregnancy body weight. Also troubling was the fact that many of the women reported taking prenatal vitamins, which typically contain 200 to 400 International Units of vitamin D.”

“Even a small decline in vitamin D concentration more than doubled the risk of preeclampsia,” noted the study’s senior author, James M. Roberts, professor and chair for research in the Pitt School of Medicine’s Department of Obstetrics, Gynecology, and Reproductive Sciences; professor of epidemiology; and MWRI founding director. “And, since newborn’s vitamin D stores are completely reliant on vitamin D from the mother, low vitamin levels also were observed in the umbilical-cord blood of newborns from mothers with preeclampsia.”

Vitamin D deficiency early in life is associated with rickets—a disorder thought to have been eradicated in the United States more than 50 years ago—as well as increased risk for type 1 diabetes, asthma, and schizophrenia.

In the developing world, preeclampsia accounts for up to 80 percent of maternal deaths. And while treatment is more 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 result from preeclampsia.

Pitt’s study was funded by the National Institutes of Health.