Placental Leak Drives Mom-to-Baby HIV Transmission

Infection appears to occur during labor contractions, new study finds

TUESDAY, Nov. 22, 2005 (HealthDay News) -- A new study finds that tiny amounts of HIV-laden blood can leak from an infected woman's placenta to her baby during labor contractions, helping to explain mother-to-child transmission of the potentially deadly virus.

"This work shows strongly for the first time that what we call placental microtransfusions during birth are responsible for a large part of the transmission of HIV from mother to baby. To our knowledge, there have never been any data like this before," principal investigator Dr. Steven Meshnick, professor of epidemiology at the University of North Carolina at Chapel Hill School of Public Health, said in a prepared statement.

He and his colleague studied 149 pregnant HIV-infected women in Malawi in Africa. By analyzing umbilical cord blood samples, the researchers concluded that HIV transmission between women and their babies occurs during labor contractions and not when the baby passes through 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 women who undergo emergency C-sections after they go into labor do transmit it. What we saw was consistent with this. It looks like direct mother-to-child blood mixing occurring during labor leads to infection," Meshnick said.

These findings suggest that methods such as sanitizing the birth canal just before birth may not be effective. It may be better to have HIV-infected pregnant women take antiretroviral drugs before they go into labor, he said.

The study was published Nov. 21 in the journal PLoS Medicine.

More information

AIDSinfo has more about HIV and pregnancy.

SOURCE: University of North Carolina at Chapel Hill, news release, Nov. 21, 2005
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