ESTIMATING THE TIMING OF MOTHER-TO-CHILD TRANSMISSION OF HUMAN-IMMUNODEFICIENCY-VIRUS IN A BREAST-FEEDING POPULATION IN KINSHASA, ZAIRE

Breast-fed infants born to human immunodeficiency virus (HIV)-infected mothers in Kinshasa, Zaire, were monitored a mean of 18 months. HIV i nfection in infants was determined by polymerase chain reaction (PCR), HIV culture, or ELISA. PCR test results for HIV DNA on venous blood d rawn from children ages 0-2 days and 3-5 months were used to estimate proportions of mother-to-child transmission and transmission risks dur ing the intrauterine, intrapartum/early postpartum, and late postpartu m periods. Among 69 HIV-infected children (26% of the cohort), 23% (95 % confidence interval [CI], 14%-35%) were estimated to have had intrau terine, 65% (CI, 53%-76%) intrapartum/early postpartum, and 12% (CI, 5 %-22%) late postpartum transmission. The estimated risks for intrauter ine, intrapartum/early postpartum, and late postpartum infection, resp ectively, were 6% (16/261; CI, 4%-10%), 18% (45/245; CI, 14%-24%), aci d 4% (8/189; CI, 2%-8%). These results support earlier studies indicat ing that most transmission occurs during labor and delivery or in the early postpartum period and that the risk of HIV transmission through breast-feeding during the postpartum period is substantial.