Affecting five per cent of first-time pregnancies, pre-eclampsia leads to abnormally high blood pressure, protein build-up in urine, and swelling in the feet and ankles.

Its causes are unknown and the only way to alleviate potentially life-threatening symptoms is to give birth.

Earlier research showed a link to a deficiency in L-arginine, an amino acid that helps to maintain a healthy blood flow during pregnancy.

Some experts have also suggested that antioxidant vitamins can help ward off the condition.

Researchers led by Felipe Vadillo-Ortego at National University in Mexico City designed a study to find out if a combination of L-arginine and antioxidants would prevent onset.

Some 750 pregnant women in Mexico City at high risk of pre-eclampsia were randomly divided into three groups.

A third received daily food bars containing both L-arginine and antioxidant vitamins, a third bars containing only vitamins, and a third placebo bars.

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 per cent in the vitamin only group, and 12.7 per cent in the L-arginine plus vitamin group.

The dietary supplement also significantly reduced the risk of premature birth compared with placebo, said the study, published online by the British Medical Journal.

“This relatively simple and low-cost intervention may have value in reducing the risk of pre-eclampsia and associated preterm birth,” the authors conclude.

Further study is needed, however, to determine whether these results can be repeated.