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Not enough is known about treating malaria in pregnancy, researchers say

July 20, 2005

Few studies compare the effects of different drug regimes in pregnant women, and many of the best studies were conducted in Southeast Asia, where malaria transmission rates are low, says researcher Lois Orton of the University of York in England.

"Reliable research about the benefits and harms of treatments for malaria in pregnant women is scarce," Orton says.

The review appears in the July issue of The Cochrane Library, a publication of The Cochrane Collaboration, an international organization that evaluates medical research. Systematic reviews draw evidence-based conclusions about medical practice after considering both the content and quality of existing medical trials on a topic.

In one of the studies analyzed by Orton and colleagues, a combination of the drugs artesunate and mefloquine was slightly better than the drug quinine at clearing malaria parasites from the bloodstream and reducing fever in pregnant women.

The risk of treatment failure was 9 percent less in the group receiving the combination drug regime, compared to treatment failure rates in the quinine group, the researchers found. The study included 106 women in Thailand.

The researchers reviewed six studies of antimalarial drugs in pregnant women in Southeast Asia and Africa. All of the women had uncomplicated malaria, meaning that they were ill and infected with the malaria parasite but not at immediate risk of dying from the disease. The studies included 513 women in their second or third trimester of pregnancy.

The studies tested a variety of antimalarial drugs, which complicated the reviewers' task of determining if any of the drug regimes should be recommended, according to Orton.

"As trials were all rather small and varied in the treatments evaluated, it is not surprising that this review was unable to demonstrate any clear direction for policy," Orton says.

One of the surprising findings of the study, according to the reviewers, was the lack of drug trials conducted in Africa, where malaria is endemic.

According to Dr. Judith Robb-McCord of Roll Back Malaria, a World Health Organization group dedicated to reducing worldwide malaria infection rates by 2010, 30 million women become pregnant each year in sub-Saharan Africa. However, malaria transmission rates in the area are so high that women may have some immunity to the disease by the time they become pregnant, preventing serious illness in some cases.

In Africa, therefore, drug trials focus on prevention rather than treatment of the disease, Orton and colleagues say.

In Asia, on the other hand, transmission rates are low and the disease is unstable, which puts pregnant women at risk for severe, life-threatening cases of malaria.

"Multiple-drug-resistant malaria is widespread in this region, so treatment options are limited and there is a push to find new drugs," Orton explains.

Research shows that pregnant women attract twice the number of mosquitoes as non-pregnant women, which probably increases their risk of contracting malaria. The disease can cause severe anemia and parasitic infection in the fetus and increase the risks of preterm birth and maternal death.

"Clearly, more trials are needed evaluating the current best regimens for malaria," Orton says.

Center for the Advancement of Health