Mother-to-child transmission of HIV-1 infection during exclusive breastfeeding in the first 6 months of life: an intervention cohort study

BACKGROUND Exclusive breastfeeding, though better than other forms of infant feeding and associated with improved child survival, is uncommon. We assessed the HIV-1 transmission risks and survival associated with exclusive breastfeeding and other types of infant feeding. METHODS 2722 HIV-infected and uninfected pregnant women attending antenatal clinics in KwaZulu Natal, South Africa (seven rural, one semiurban, and one urban), were enrolled into a non-randomised intervention cohort study. Infant feeding data were obtained every week from mothers, and blood samples from infants were taken monthly at clinics to establish HIV infection status. Kaplan-Meier analyses conditional on exclusive breastfeeding were used to estimate transmission risks at 6 weeks and 22 weeks of age, and Cox's proportional hazard was used to quantify associations with maternal and infant factors. FINDINGS 1132 of 1372 (83%) infants born to HIV-infected mothers initiated exclusive breastfeeding from birth. Of 1276 infants with complete feeding data, median duration of cumulative exclusive breastfeeding was 159 days (first quartile [Q1] to third quartile [Q3], 122-174 days). 14.1% (95% CI 12.0-16.4) of exclusively breastfed infants were infected with HIV-1 by age 6 weeks and 19.5% (17.0-22.4) by 6 months; risk was significantly associated with maternal CD4-cell counts below 200 cells per muL (adjusted hazard ratio [HR] 3.79; 2.35-6.12) and birthweight less than 2500 g (1.81, 1.07-3.06). Kaplan-Meier estimated risk of acquisition of infection at 6 months of age was 4.04% (2.29-5.76). Breastfed infants who also received solids were significantly more likely to acquire infection than were exclusively breastfed children (HR 10.87, 1.51-78.00, p=0.018), as were infants who at 12 weeks received both breastmilk and formula milk (1.82, 0.98-3.36, p=0.057). Cumulative 3-month mortality in exclusively breastfed infants was 6.1% (4.74-7.92) versus 15.1% (7.63-28.73) in infants given replacement feeds (HR 2.06, 1.00-4.27, p=0.051). INTERPRETATION The association between mixed breastfeeding and increased HIV transmission risk, together with evidence that exclusive breastfeeding can be successfully supported in HIV-infected women, warrant revision of the present UNICEF, WHO, and UNAIDS infant feeding guidelines.