Research offers the prospect that pregnant women can soon be screened for it.
Researchers have demonstrated that women likely to develop a dangerous vascular condition late in their pregnancies have measurable diminished levels of a protein critical to placental growth more than a month before they develop symptoms.
The research, described today in the Journal of the American Medical Association, offers the prospect that pregnant women can soon be routinely screened for the condition, called preeclampsia, which develops in about 5 percent of all pregnancies and affects about 200,000 women in the United States each year. In less developed nations, the condition is a leading cause of maternal and infant death.
The disease is marked by a narrowing of blood vessels that supply the placenta, high blood pressure and water buildup in cells and tissues. In some women, the condition becomes more extreme, advancing to eclampsia, which brings about a series of potentially fatal seizures and coma. While the seizures and high blood pressure can be treated, the only cure for preeclampsia is delivery of the baby.
Even if the condition doesn't result in seizures, many infants born to women with preeclampsia are born prematurely or, if full term, are extremely small. This puts them at increased risk for complications that include blindness, cerebral palsy or mental retardation.
Some women, like those who already have high blood pressure or are carrying more than one baby, are known to be at high risk for the condition. But for most, the only way to detect it is through regular monitoring of blood pressure throughout the pregnancy and testing for abnormal protein levels in the urine during the last three months.
"By the time a rise in blood pressure has been detected, it may already be too late, as the condition can very rapidly spiral out of control," said Dr. Ananth Karumanchi, a kidney specialist at Beth Israel Deaconess Medical Center in Boston and lead author of the study.
"This finding sets the stage for development of a test to screen women for high risk of preeclampsia," said Dr. Duane Alexander, director of the National Institute of Child Health and Human Development, which sponsored the study and had several researchers involved in the project.
Using archived urine specimens collected by NICHD over the course of pregnancy, the researchers looked at levels of placental growth factor in 118 women who did not develop preeclampsia and 120 women who did. Among the latter group, low levels of the protein were apparent beginning in the 25th week of pregnancy.
"A simple urine test could help predict the onset of this disease one to two months before the onset of clinical symptoms, and that could make a tremendous difference in outcomes for patients, in particular women who have limited access to specialized medical care," Dr. Karumanchi said.
While a urine screening test would likely be fairly inexpensive compared to blood-protein tests that are now done later in pregnancy, Dr. Richard Levine of the NICHD noted that a few of the 118 women who did not develop preeclampsia also had low levels of the protein, and thus a confirming blood test for another protein thought to play a role in the disease might be needed.