Preventing HIV-infected pregnant women from transmitting the virus to their newborns has long been a major concern for obstetricians. As such, many doctors continue to debate the benefits of elective Caesarian section as a way to protect the infant.
In high-risk pregnancies, where the viral loads can't be suppressed with medication, delivering a baby by C-section directly from the protected, sterile environment of the amniotic sac can limit the risk of HIV transmission. But in lower-risk pregnancies, where antiretroviral medications keep the virus in check, the risk of transmitting HIV to a newborn is only about 1 percent to 2 percent.
A new study by researchers at Johns Hopkins and the National Institutes of Health demonstrates that uncomplicated labor and vaginal delivery does not stimulate the babies' immune systems. Results are scheduled to be presented Jan. 18 at the annual meeting of the Society for Maternal-Fetal Medicine in New Orleans.
A research team led by Hopkins obstetrician Helene Bernstein, M.D., Ph.D., studied lymphocytes from the umbilical cords of 23 babies born by vaginal delivery or elective C-section, as well as cells taken from eight babies born to mothers who had chorioamnionitis (a bacterial infection of the amniotic sac) or preterm labor.
None of the women had HIV. Checking for specific biochemical markers of white blood cell activation, they found the level of cell activity to be similar among babies born by either method. In addition, when HIV was introduced to these cells in the laboratory, there was no difference in their ability to be infected.
However, the babies born to mothers with chorioamnionitis or preterm labor did show activation of their white blood cells. When HIV was introduced to the white blood cells in the laboratory, there were more infections and the virus grew quickly, meaning that these infants could be at higher risk for HIV transmission if born to HIV-infected mothers with these prenatal conditions. In addition, these babies had higher levels of CCR5, a molecule that HIV uses to infect cells.
"These results help us understand why children born to HIV-infected mothers with chorioamnionitis or preterm labor have a higher risk of transmission," says Bernstein, an instructor of gynecology and obstetrics.
"Physicians may want to consider these findings when caring for infants at risk for HIV transmission after these problems. Other potential implications for clinical practice may include more aggressive treatment of HIV-infected mothers with these prenatal conditions."
Other study authors include Audrey Kinter, Tae-Wook Chun, Robert Jackson and Claire Hallahan, all of the National Institute of Allergy and Infectious Diseases, part of the National Institutes of Health.
Abstract # 41230: Bernstein, H. et. al., "The effect of elective C-section, preterm labor and chorioamnionitis on fetal lymphocyte activation and susceptibility to HIV infection."
Related Web sites:
Women's health services at Johns Hopkins
http://www.hopkinsmedicine.org/women.html
Society for Maternal-Fetal Medicine
http://www.smfm.org/
National Institute of Allergy and Infectious Diseases
http://www.niaid.nih.gov/default.htm
Media Contact: Karen Blum 410-955-1534, Email: kblum@jhmi.edu
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