Scientists studying the pregnancy complication pre-eclampsia say a dietary supplement containing an amino acid and antioxidant vitamins given to expectant mothers at high risk could reduce occurrence of the disease.

In a study in the British Medical Journal (BMJ) on Friday, researchers found that pregnant women taking supplements with the amino acid L-arginine plus vitamins were significantly less likely to develop pre-eclampsia compared with those taking just vitamins, or those taking a placebo supplement.

Pre-eclampsia is a serious condition marked by abnormally high blood pressure and high protein levels in the urine. It affects about 5 percent of all first-time pregnancies and is dangerous for both mother and child.

Experts estimate that the cost of treating women with pre-eclampsia is $45 billion a year in the United States, Europe, Asia, Australia and New Zealand. In developing countries, an estimated 75,000 women die of it each year.

If mothers and their babies survive, the women later have a higher risk of high blood pressure, heart disease, stroke and diabetes. The babies are often born prematurely and can suffer complications later in life.

Pre-eclampsia is thought to be linked to a deficiency in L-arginine, an amino acid that helps to maintain a healthy blood flow during pregnancy. Some experts also think that antioxidant vitamins can help protect against the condition.

This study took place at a hospital in Mexico City. Pregnant women at high risk of pre-eclampsia received either daily food bars containing both L-arginine and antioxidant vitamins, bars containing vitamins only, or placebo "dummy" bars containing no L-arginine or vitamins. The supplements began when women were around 20 weeks pregnant and continued until delivery.
The proportion of women developing pre-eclampsia was 30.2 percent in the placebo group, 22.5 percent in the vitamin only group, and 12.7 percent in the L-arginine plus vitamin group.

"This relatively simple and low cost intervention may have value in reducing the risk of pre-eclampsia and associated preterm birth," the researchers, from Mexico and the United States, wrote in their study.

Two British experts commenting on the work in the BMJ said it was an important finding but crucial questions remained.

Before any more trials were started, they said, researchers should seek to establish how L-arginine and vitamins work together, what the potential harmful effects might be, and what the results might be in other populations and places.