A simple urine test during pregnancy could someday predict which women are likely to develop dangerously high blood pressure called pre-eclampsia, a condition that kills hundreds of mothers-to-be each year in the United States and leads to 15 percent of all premature births, researchers say.

Pre-eclampsia occurs in as many as 8 percent of U.S. pregnancies, often striking healthy women without warning, and can lead to seizures, strokes and kidney damage. The cause is unknown, and there is no reliable way in use today to predict who will develop it. The only known cure is to deliver the baby, often prematurely.

But a new study offers hope for the development of a urine test over the next few years that could identify high-risk women several weeks or even months before pre-eclampsia develops.

The study found that urine samples from women who eventually developed pre-eclampsia had extremely low levels of a protein called placental growth factor, which nurtures blood vessels that support the mother and fetus.

The same researchers reported last year that blood samples also can predict the disease. But they said a urine test could allow women to screen themselves.

While a screening test would not prevent the disorder, doctors could monitor at-risk women more closely, and such patients could be put on blood pressure drugs or medication to prevent seizures.

The study was published in today's Journal of the American Medical Association.