A new study says pregnancy may help protect HIV-positive women from developing full-blown AIDS. The study appears in the October 1st issue of the Journal of Infectious Diseases.

Dr. Timothy Sterling of Vanderbilt University is the senior author of the study. He says there were surprising findings for HIV-positive women who were taking anti-retroviral drugs.

?We found that the women who became pregnant during the study period had a lower risk of progressing to AIDS-defining events or death than the women who did not become pregnant. This was an observational study just looking at 759 women who were seen at some point during the study period, which was between January 1997 and December 2004,? he says.

Sterling says no one knows for sure yet why this happened, but it appears the immune systems of the pregnant women were working better.

?We know that the women who became pregnant were healthier than the women who did not. In other words, they had a higher CD-4 (immune system cells) count, a lower viral load. They were younger. They were also more likely to receive therapy. We performed analyses that adjusted for those factors and found that the women who became pregnant were still less likely to progress to AIDS or death,? he says.

He says another study is needed to try to formally pinpoint the reason for the benefit.

?It could be that the pregnant women were highly motivated to have their HIV treated, obviously to prevent transmission into the fetus, and to take as good care of themselves as possible. Perhaps that additional motivation facilitated them in doing better. The women who are pregnant and followed at the comprehensive care center where this patient population was seen have more intensive care. They have more frequent visits. They?re more prone to get dietary supplements. (They?re) less likely to be abusing drugs. So, there are a number of factors that could have played a role,? he says.

Earlier studies, conducted before the use of anti-retroviral drugs, indicated that pregnancy showed either no increased risk of AIDS progression or a slight increased risk.

In an accompanying editorial in the Journal of Infectious diseases, Dr. Kathryn Anastos writes, ?For women in higher-resource settings and perhaps for women in lower resource settings, the findings?are extremely important.? She adds, ?Women can now have greater confidence that, in addition to protecting their children from mother-to-child transmission with antiretroviral drugs, their own health will not be compromised by pregnancy.?

Anti-retrovirals are becoming more available in developing countries, but many health officials and groups say much greater access is needed.