Scientists assessed the impact of a supplement containing an amino acid and antioxidant vitamins.
Pre-eclampsia affects up to one in 10 pregnant women and is believed to be linked to problems with blood vessels in the placenta.
The complication usually occurs after 20 weeks and is life-threatening to the baby or mother in around 10% of cases.
The symptoms include high blood pressure, headaches, blurred vision and swelling.
Some experts believe the condition is linked to a deficiency in L-arginine, an amino acid that helps to maintain a healthy blood flow. Others think antioxidants could help protect women.
In the latest study, published in the British Medical Journal (BMJ), 30.2% of women in a placebo group developed pre-eclampsia, dropping to 22.5% in the antioxidant vitamin-only group, and 12.7% in the L-arginine plus vitamin group.
The results showed that those given L-arginine plus vitamins were significantly less likely to develop pre-eclampsia.
But antioxidant vitamins alone did not significantly reduce the risk.
The team also found that L-arginine plus vitamins significantly reduced the risk of premature birth compared with placebo.
The researchers, from universities in the US and Mexico, called for more studies but concluded: “We observed a significant reduction in the incidence of pre-eclampsia/eclampsia in pregnant women who consumed bars containing L-arginine plus antioxidant vitamins.
“The results of this trial support the proposed hypothesis that supplemental L-arginine can reduce the risk of pre-eclampsia.”
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