UCSF scientists have discovered how a defect in the placenta may give rise to the common and sometimes life-threatening complication of pregnancy called preeclampsia.

The team -- led by Susan Fisher, PhD, a professor of stomatology and obstetrics and gynecology -- found that preeclampsia results from a failure of the placenta to invade the wall of the uterus and to appropriately mimic the tissue which lines blood vessels. The discovery could help immensely in the search for ways to diagnose and treat the disorder, which could send a pregnant women's blood pressure.

The study, funded by the National Institute of Child Health and Human Development, was published in the May 1 issue of the Journal of Clinical Investigation.

About 7 percent of first-time mothers and 1 to 2 percent of mothers having subsequent pregnancies develop preeclampsia. The condition occurs suddenly without warning and sometimes in as little as a few hours. Usually, a pregnant women with preeclampsia develops dangerously high blood pressure and begins secreting protein in the urine. In some cases, the condition may progress to eclampsia, a series of potentially fatal seizures. Preeclampsia is still one of the leading causes of maternal mortality. The need to screen and detect the condition early was one of the original reasons the medical community many years ago began recommending regular prenatal visits.

Although the high blood pressures accompanying preeclampsia can be treated with drugs, the only effective treatment for the condition is immediate delivery of the baby.

Earlier studies had shown that in women who develop preeclampsia, the placenta fails to penetrate the wall of the uterus adequately, says Fisher. In the new study, Fisher and co-investigators Caroline Damsky, PhD, and Yan Zhou of the School of Dentistry's department of stomatology, determined that in normal pregnancies, fingerlike projections of placental cells, known as cytotrophoblasts, invade the inside wall of the uterus and then begin to mimic the vein and artery cells found on the inside of blood vessels. Eventually, these placental projections break down the vessels, allowing the placenta to be bathed in maternal blood. This blood carries oxygen and nutrients to the placenta, and carries away fetal wastes.

In preeclampsia, however, this process goes awry. Researchers theorize that the failure of invading cytotrophoblasts to take on the characteristics of blood vessel cells may provoke a reaction in the circulatory system of the mother, resulting in high blood pressure and causing blood vessel damage.

1st appeared 5/5/97