An international study has found that elective caesarean sections, coupled with anti-retroviral therapy, can reduce the incidence of HIV transmission from mother to infant to 2 percent, a nearly 10-fold decrease compared to mothers who received neither treatment. The study, in which a team from Yale participated, was published in April in the New England Journal of Medicine. The principal investigator for the Yale team, Warren A. Andiman, M.D., professor of pediatrics and epidemiology, said the study by the International Perinatal HIV Group could change approaches to delivery of infants of HIV-positive mothers.

“My feeling is that the usual practice in the United States will be to do a C-section,” Andiman said. “Obstetricians will have to think of compelling reasons not to provide caesarean sections for their patients with HIV.”

Physicians were already using elective C-sections to prevent transmission of other infectious diseases, such as herpes simplex. “It has been long held that being born vaginally poses a risk,” said B. Joyce Simpson, R.N., M.P.H., pediatric HIV coordinator at the Pediatric AIDS Care Program, and co-leader of the Yale study. But when it came to vertical transmission of HIV, no single study, either in the United States or in Europe, included a sample large enough to provide statistically significant results. Moreover, most data did not distinguish between controlled, elective C-sections and emergency C-sections, which are almost as likely as vaginal delivery to result in HIV infection in the infant. To prevent transmission of HIV, the C-section must be done before labor has begun and membranes have ruptured, Andiman said.

The National Institute of Child Health and Human Development organized the international study, which included mother-child pairs who were studied prospectively, some beginning in 1982. It was comprised of 15 study sites in the United States and Western Europe, including Yale’s Prospective Longitudinal Cohort Study. More than 8,500 cases were reviewed to ensure that all data conformed to the study’s strict guidelines. They found that elective C-section, without anti-retroviral therapy, reduced the incidence of HIV transmission from 19 percent to 10 percent. Elective C-sections combined with anti-retroviral therapy, including AZT given during pregnancy and at delivery, reduced the rate of transmission to 2 percent.