November 23, 2005
Small tears in the placenta of HIV-positive pregnant women might allow the virus to pass from the woman's blood to the infant during delivery and could play a role in mother-to-child transmission, according to a study published on Tuesday in PLoS Medicine, VOA News reports (Berman, VOA News, 11/22). Steven Meshnick, a professor of epidemiology at the University of North Carolina-Chapel Hill School of Public Health, and colleagues in 2003 examined 149 pregnant, HIV-positive women in Malawi. Each woman received one dose of an antiretroviral drug to reduce the risk of vertical HIV transmission (Bowman, Scripps Howard/Washington Times, 11/22). Researchers then measured the amount of a placental protein, which normally is too large to pass through the placenta, in the umbilical cord blood of each woman. Infants had a higher risk of HIV infection when there was more placental protein in the umbilical cord blood, the researchers found (VOA News, 11/22). The researchers said that HIV transmission could happen during labor when contractions occur, rather than the infant is in the birth canal. "It has been known for a long time that HIV-infected women who undergo caesarean section before they go into labor do not transmit the virus, whereas those who underwent emergency c-sections after they go into labor do transmit it," Meshnick said, adding that the new data is consistent with that information (Scripps Howard/Washington Times, 11/22).
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