HIV transmission risk during breast feeding was greatest during the early months of life

Design Cohort study with 24 month follow up. Setting A tertiär)- care hospital in Blantyre, Malawi. Participants 672 infants who were born to HIV infected women who had not received antiretroviral drugs during pregnancy or after childbirth. Infants had to be HIV negative on die first postnatal visit at 6 weeks of age, be breast fed, and have a second follow up visit Assessment of risk factors Time of infant HFV infection through breast feeding was taken to be the midpoint between the last postnatal negative polymerase chain reaction (PCR) test result and die first postnatal positive PCR test result Time at risk for infant HIV infection through breast feeding was the interval between die first postnatal negative PCR test result and die first postnatal positive PCR test result Potential risk factors assessed included mother's age, maternal symptoms of HIV or death \rithin 2 years of giving birth, parity, delivery mode, breast problems (painful swelling, other signs of infection, or cracked or bloody nipples), and infant's birdiweight Main outcome measure HIV infection in infants determined by PCR testing. Both HIV antibody (enzyme linked immunosorbent assay) testing and immunoblotting were used to confirm HIV infection in infants 515 months of age. Main results 47 infants (7%) became infected with HIV through breast feeding. The cumulative risk for infection after 5, 11,17, and 23 mondis was 3.5%, 7.0%, 8.9%, and 10.3%, respectively. The HIV infection incidence rates per person mondi were 0.7% during mondis 1 to 5 and decreased to 0.2% during mondis 18 to 23 (p = 0.01 for trend). Univariate analysis showed that die only risk factor associated with HIV transmission was low parity; higher parity was protective (<4 v &4 infants; relative risk [RR] 0.4,95% CI 0.2 to 0.9). The greatest risk was to second born infants. Using multivariate analysis, the protective association of higher parity was maintained (RR 0.2, CI 0.09 to 0.6), and older maternal age (25 y) was also protective (RR 0.4, CI 0.2 to 0.8). Conclusions In HIV positive mothers, the risk for HIV transmission to their breast feeding infants was greatest during 1 to 5 months of age. Higher parity and older maternal age Were associated with a lower risk for transmission.