"We cannot generalize our findings beyond the Rakai setting and it would be important for other investigators to verify our results. However, if women are at increased risk of HIV acquisition during pregnancy, our findings represent a public-health problem, both for the mother and possibly her unborn infant," said the study's lead author Ronald Gray, MD, the Robertson Professor of Reproductive Epidemiology in the Bloomberg School's Department of Population and Family Health Sciences. "We believe that it would be prudent to warn women of this potential risk of HIV acquisition during pregnancy and promote safe sex or sexual abstinence where feasible."
The study supports the findings of two previous studies that reported a greater risk of acquiring HIV during pregnancy than after delivery. However, neither study accounted for risk factors that contribute to HIV risk.
Gray and his colleagues assessed 2,188 HIV-negative women who were sexually active and were pregnant or breastfeeding, and compared their rates of HIV acquisition to 8,473 women who were neither pregnant nor lactating. They compared the incidence rates of HIV during pregnancy and breastfeeding with the rates during intervals when pregnancy and breastfeeding were absent. The sexual behaviors of husbands of married women in the study were also assessed.
According to the investigators, the rate of HIV acquisition was higher during intervals of pregnancy than during breastfeeding or during inter vals with neither. The results of the study showed HIV incidence rates during pregnancy were 2.3 percent per year whereas HIV incidence rates were 1.3 percent per year during breastfeeding and 1.1 percent per year for women who were not pregnant or breastfeeding. The risk for HIV remained higher even after the investigators adjusted for other HIV risk factors.
"It is unlikely that the change in HIV risk we observed is due to sexual behaviors. It may be attributed to hormonal changes affecting the genital tract mucosa or immune responses," said Gray.