Effect of Breastfeeding on Transmission of HIV-1

Abstract

Source: Nduati R, John G, Mbori-Ngacha D, et al. Effect of breastfeeding and formula feeding on transmission of HIV-1. JAMA. 2000;283:1167–1174.HIV-1 transmission may occur during breastfeeding, but the magnitude of risk has not been precisely defined. This randomized clinical trial was done to measure the frequency of breast milk transmission of HIV-1 and to compare mortality rates and HIV-1–free survival between breastfed and formula-fed infants. From 1992 to 1998, HIV-1–seropositive women were enrolled from prenatal clinics in Nairobi, Kenya. Mother-infant pairs were randomized to either breastfeeding (n=212) or formula feeding (n=213), with a median follow-up of 24 months. Compliance with an assigned feeding method was 96% in the breast-feeding arm and 70% in the formula arm (P<.001). The median duration of breastfeeding was 17 months. Of 401 woman-infant pairs still in the study at delivery, 94% of infants were followed to endpoints of either HIV-1 infection status at 2 years (83% follow-up) or death (93% follow-up). The cumulative probability of HIV-1 infection at 24 months was 36.7% (95% CI, 29.4–44.0) in the breastfeeding arm and 20.5% (95% CI, 14.0–27.0) in the formula arm (P=.001). The estimated excess rate of transmission of HIV-1 infection by breastfeeding was 16.2% (95% CI, 6.5–25.9). In the breast-feeding arm, 44% of HIV-1 infection was attributable to breast milk. Most breast milk transmission occurred early—75% of the risk difference by 6 months—although transmission continued to occur with later exposure. The 2-year mortality rate was similar in both arms—24.4% with breastfeeding vs 20.0% formula feeding (P=.30)—but the rate of HIV-1-free survival at 2 years was lower in the breastfeeding arm: 58.0% vs 70% with formula feeding (P=.02).These findings are important to resource-poor countries, where formula feeding carries a high risk of diarrheal mortality and, therefore, breastfeeding is preferred. The findings are also relevant to North American pediatricians who counsel new mothers about feeding when their HIV-1 status is not known. In New York State, newborn HIV-1 testing is mandatory, but prenatal testing is only recommended and frequently not obtained. Often neither maternal nor newborn HIV-1 infection status is known at birth. Should such mothers be advised not to breastfeed until their HIV-1 status is determined and perhaps risk breastfeeding failure? This study, as well as others,1 provides sobering data that weighs against nursing until the HIV-1 status is known. There was some noncompliance with treatment assignment in this study, particularly among women assigned to formula feeding in a country where breastfeeding is the norm. Breast-feeding by those assigned to the formula group only strengthens the study’s findings since it would tend to dilute the real risk in the breastfeeding group. More vigorous prenatal maternal HIV-1 testing might help to prevent vertical transmission, and partner HIV-1 testing should also be advised to clarify ongoing risk of postnatal maternal infection and infant acquisition of HIV-1 via breast milk.