NEW YORK, Mar 27 (Reuters Health) - British researchers have identified a maternal blood flow defect that appears to play a role in preeclampsia--a leading contributor to complications during labor and childbirth.

But vitamin C infusions appeared to reverse the problem, according to a report in the March 28th issue of The Journal of the American Medical Association.

Preeclampsia occurs when a pregnant woman develops high blood pressure, swelling in the legs and other symptoms. The complication affects as many as 1 in 10 first pregnancies. If left untreated, preeclampsia can worsen and become eclampsia, in which a woman has convulsive seizures in late pregnancy or during the first week after delivery. Untreated eclampsia can be fatal to both the mother and the fetus.

Women who have had preeclampsia have blood vessels that are less able to widen, even years after pregnancy, Dr. John C. Chambers and colleagues from the Imperial College School of Medicine in London, UK, found. And this problem is worse in women who had more than one episode of preeclampsia.

The investigators measured blood flow in the arteries of 113 women who had experienced one or more episodes of preeclampsia and 48 women who had had normal pregnancies. On average, the women had delivered babies 3 years before the study.

In a subgroup of 30 patients, including 15 women with a history of preeclampsia and 15 women who had experienced normal labor and delivery, the researchers tested blood flow before and after giving each of the women a dose of vitamin C intravenously. The vitamin improved blood flow in women who had had preeclampsia, but had no effect on women without the complication.

While researchers have known that blood vessel problems occur during preeclampsia, this is the first time scientists have looked at a mother's blood vessel response independent of the placenta.

Scientists have proposed that oxygen free radicals may be responsible for impaired blood vessel response, and the new study findings support this hypothesis. Free radicals are molecules that are byproducts of the body's normal processes. Because free radicals react strongly with many types of other molecules, they can damage body tissues.

Antioxidants--such as vitamin C and vitamin E--can lessen this damage by "scavenging" these free radicals, Chambers and colleagues note.

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