C-Sections Before Labor and Rupture of Membranes Reduce the Risk of Maternal-Infant HIV Transmission by Half

National Institute of ChildHealth, and Human DevelopmentEMBARGOED FOR RELEASE, Thursday, January 28, 1999, 10:00 AM ESTEarly Release of NEJM Information, Robert Bock, John McGrath

The largest, most comprehensive analysis of its kind has found that pregnant women infected with HIV can reduce the risk of transmitting the virus to their infants by about 50 percent if they deliver by elective cesarean section -- before they have gone into labor and before their membranes have ruptured, according to a study led by a researcher at the National Institute of Child Health and Human Development (NICHD).

The article describing the study will be published in the April 1 issue of The New England Journal of Medicine. Because of the study's immediate potential in reducing HIV transmission, however, the journal's editors have decided to release the article early. As of 10 a.m. January 28, 1999, the article will be available on the Journal's website at http://www.nejm.org.

This finding can prevent needless suffering and loss of life, said NICHD Director Duane Alexander, MD. A c-section presents risks to the mother, so each case must be evaluated individually -- but this fact is striking: c-sections cut mother-to-child HIV transmission by at least 50 percent.

In the study, an individual patient data meta-analysis, elective cesarean section was defined as cesarean section performed before rupture of the membranes and before the beginning of labor.

The main analysis included 8533 mother and child pairs from 5 European and 10 North American studies, said the study's leader, Jennifer S. Read, a medical officer with NICHD's Pediatric, Adolescent, and Maternal AIDS Branch. HIV-infected women who were breastfeeding their infants were not included in this study, to rule out the possibility of the virus being transmitted via breast milk.

The mothers who took part in the studies were divided into four groups: those who had elective cesarean section, those who had a cesarean section after rupture of membranes and/or after labor began, those who delivered vaginally with assistance from forceps or vacuum suction, and those who delivered vaginally with neither forceps nor vacuum suction.

The main analysis compared the likelihood of HIV infection among 857 children whose mothers delivered by elective cesarean section to that of 7676 children whose mothers delivered by other modes of delivery. The likelihood of mother-infant transmission of HIV was decreased by approximately 50 percent among children whose mothers delivered by elective cesarean section. The results were essentially unchanged when other factors were taken into consideration, including: receipt of antiretroviral drugs by the mother and child, how advanced the mother's HIV-related disease was, and the infant's birth weight.

Of the 5944 mothers who did not receive AZT or other antiretroviral drugs during pregnancy and during labor and whose children did not receive such drugs during the first few weeks of life, 10.4 percent of the mothers who delivered by elective c-section transmitted the virus to their infants, as compared to 19 percent of the women who delivered by the other modes of delivery. Of the 1451 mothers who did receive antiretroviral drugs during pregnancy and during labor and whose children received such drugs during the first few weeks of life, 2 percent of those who delivered by elective c-section transmitted the virus to their infants, as compared to 7.3 percent who delivered by other means.

HIV-infected women had a decreased likelihood of transmitting the virus with elective cesarean section as compared with other modes of delivery, Dr. Read said. She noted that the potential benefit of elective cesarean section with regard to decreasing the transmission of HIV from mother to child must be weighed against the possibility of increased post-operative infections and other problems among HIV-infected women.

Previous studies of the potential benefit of cesarean delivery in reducing HIV transmission from mother to infant had produced conflicting results, probably due to the smaller numbers of patients in some of the studies and the combining of cesarean deliveries performed both before and after labor began or after rupture of membranes had occurred. Obtaining the original data, combining the studies to increase the numbers, and separating elective cesareans from others, provided the clear-cut results in this meta-analysis.

"The results of this meta-analysis suggest a potential role for elective cesarean section as an additional intervention to decrease mother-child HIV transmission, irrespective of concomitant receipt or lack of receipt of AZT prophylaxis," Dr. Read said.

The study results were originally presented at the 12th International Conference on AIDS in Geneva, Switzerland on June 30, 1998.