A substance found in the urine of pregnant women can be measured to predict the later development of preeclampsia, according to research from the National Institute of Child Health and Human Development of the National Institutes of Health.
"We may have reached a turning point in the extensive federal research investigation of this frequent, life- threatening complication of pregnancy," said Duane Alexander, M.D., Director of the NICHD. "This finding sets the stage for the development of a test to screen women for high risk of preeclampsia. Once these women are identified through such a test, we can target studies to find effective ways to prevent its progression or to keep the most dangerous complications from occurring."
The researchers found women were highly likely to develop preeclampsia if they had low levels of a substance known as placental growth factor (PlGF) in their urine. PlGF works in combination with a substance called vascular endothelial growth factor (VEGF). Together, the two substances foster the growth of new blood vessels, and maintain the health of cells that line the inside of blood vessels, including those in the placenta that support the developing fetus. The researchers believe that the high blood pressure and other symptoms characteristic of preeclampsia result from low levels of PlGF and VEGF.
Researchers are making plans to refine the finding into an accurate clinical test.
The study appears in the January 5 "Journal of the American Medical Association". It was conducted by researchers at the NICHD, Harvard University Medical School, the Harvard School of Public Health, Beth Israel Deaconess Medical Center, Allied Technology Group, and the University of Cincinnati College of Medicine. Much of the funding for the study was provided by the NICHD and another of the NIH Institutes, the National Institute of Diabetes and Digestive and Kidney Diseases.
A few women - such as those pregnant with more than one baby or with long-term high blood pressure - are known to be at high risk for preeclampsia, explained the study's first author, Richard Levine, M.D., M.P.H., of NICHD's Division of Epidemiology, Statistics, and Prevention Research. However, the vast majority of cases strike without warning, in first-time mothers. Usually, a pregnant woman with preeclampsia develops dangerously high blood pressure and begins excreting protein in the urine. In some cases, the condition may progress to eclampsia, a series of potentially fatal seizures. Although the high blood pressure and seizures can be treated, the only cure for preeclampsia is delivery of the baby. Combined estimates of preeclampsia and other hypertension disorders during pregnancy range from 5.9 to 8 percent of all pregnancies in the United States.
In cases where the condition does not progress to eclampsia, infants born to mothers with preeclampsia may be extremely small for their gestational age or may be born prematurely. These conditions, in turn, place the infants at risk for a variety of other birth complications, among them blindness, cerebral palsy, or mental retardation.
To conduct the study, the researchers analyzed stored urine samples of 120 women who developed preeclampsia and compared them to samples from 118 women who did not develop preeclampsia. The analysis was performed on stored samples collected at three intervals during the women's pregnancies. The urine samples were collected as part of a separate NICHD study published in 1997, which found that pregnant women could not lower their chances of getting preeclampsia by taking calcium supplements.
In the current study, urinary levels of PlGF were significantly lower for the women who subsequently developed preeclampsia than they were for the 118 women who did not develop the condition. For the women who developed preeclampsia, low levels of PlGF were apparent beginning at the 25th through the 28th week of pregnancy. The differences in P1GF levels grew more pronounced by the 29th through the 36th week of pregnancy.
