FRIDAY, May 20 (HealthDay News) -- Though a new study suggests that a dietary supplement could lower the likelihood that high-risk pregnant women will develop preeclampsia, the jury is still out over whether it actually works and a specialist recommends that women not try it yet.

Preeclampsia is a pregnancy complication that can boost blood pressure to abnormally high levels, causing hypertension. It affects about 5 percent of first pregnancies.

"Women die of uncontrolled hypertension through stroke or multi-organ failure," said Dr. David Williams, an obstetrician and consultant in maternal medicine at University College London Hospitals, who co-wrote a commentary accompanying the study, which was published online May 19 in BMJ.

"Comprehensive prenatal care and modern medical practice in developed countries makes maternal mortality from preeclampsia a rare event, but it accounts for 20 percent of maternal mortality in many developing countries," Williams explained.

Scientists suspect that low levels of an amino acid called L-arginine could play a role in the development of the disease, and some have wondered whether antioxidant vitamins could lower the risk of the condition.

For the study, researchers in Mexico assigned high-risk pregnant women to one of three groups: 228 ate food bars containing L-arginine and antioxidant vitamins; 222 ate bars with vitamins only; and 222 ate bars that didn't contain the amino acid or the vitamins, considered the placebo group.

After eating the food bars daily from 20 weeks into their pregnancy through delivery, only 13 percent of the women who ate bars with L-arginine plus antioxidants developed preeclampsia; they also were less likely to give birth prematurely. In the vitamins-only group, 23 percent developed preeclampsia, as did 30 percent of women in the placebo group.

"This relatively simple and low-cost intervention may have value in reducing the risk of preeclampsia and associated preterm birth," the study concluded.

But the authors of the accompanying commentary raise questions about possible harmful effects and suggest there needs to be more research to understand "the numerous inconsistent strands of evidence relating to L-arginine and its possible effects on preeclampsia."

Williams said: "We still do not understand the complex, interacting ways in which preeclampsia develops, and it is likely to be different in different women. More work needs to be done to understand the potential of L-arginine with antioxidant vitamins, and at this stage, we do not recommend that this supplementation should be given to women at risk of preeclampsia."

More information

For more about preeclampsia, visit the U.S. National Library of Medicine.