Daily doses of multivitamins can reduce fetal deaths and premature births and improve the immune systems of pregnant women infected with HIV, researchers said Friday.

A four-year study of 1,075 HIV-positive pregnant women in Tanzania, reported in The Lancet medical journal, showed that vitamin supplements reduced fetal deaths, low birth weights and severe preterm births by approximately 40 percent.They also significantly improved the immune status of the mothers.

"While there has been much excitement in the U.S. and elsewhere concerning access to newly developed combination anti-viral therapies which include protease inhibitors, these are so expensive that the great majority of those infected with the AIDS virus have no access to them," Wafaie Fawzi, who led the research team, said in a statement.

"The idea of this study was to determine whether an inexpensive intervention would have at least some protective effect," added Fawzi, of the Harvard School of Public Health.

For the 90 percent of the world's 30 million HIV sufferers who live in the developing world, the study could have a profound impact. Protease inhibitors are beyond the financial means of most HIV victims, but vitamin supplements cost just cents per day.

Fawzi and his colleagues are not yet sure if the supplements reduced transmissions of the disease from mother to child.

But they believe the mother's improved immune system may lead to greater fetal immunity and a lower risk of death and malnutrition.

The researchers did not examine whether the vitamins slowed the clinical progression of the virus.

During the trial, the women were divided into four groups. One group received only vitamin A, the second was given multivitamins but no vitamin A, the third had both and the fourth was given a placebo, or dummy pill.

There were 40 fetal deaths among the women who took the multivitamins, compared with 49 among those not on supplements.

The risk of low birth weight, less than 5.5 pounds, was reduced by 44 percent and births earlier than 34 weeks gestation were cut by 43 percent in the multivitamin group.

Fawzi said vitamin A had no significant effect on the outcomes.