Effect of perinatal zidovudine prophylaxis on the evolution of cell-free HIV-1 RNA in breast milk and on postnatal transmission.

Perinatal zidovudine (ZDV) prophylaxis decreases rates of perinatal transmission of human immunodeficiency virus type 1 (HIV-1). Its relationship with levels of HIV-1 RNA in breast milk and postnatal transmission in breast-fed African children is unknown. At day 8 after delivery, levels of HIV-1 RNA in breast milk from 28 women who transmitted HIV-1 (Ts) postnatally and from 130 women who did not transmit HIV-1 (NTs) were lower for women receiving ZDV than for women receiving placebo. Levels of HIV-1 RNA in breast milk remained low over time in NTs but increased by 8-16-fold in Ts treated with ZDV from baseline to days 45/90 after delivery. Levels of HIV-1 RNA in breast milk at day 8 after delivery and the increase in levels of HIV-1 RNA in breast milk from day 8 to days 45/90 after delivery were independently associated with postnatal transmission. An increase in the levels of HIV-1 RNA in breast milk from day 8 to 45 after delivery was associated with maternal ZDV prophylaxis. The rebound in levels of HIV-1 RNA in breast milk after discontinuation of maternal antiretrovirals needs to be further explored--it may justify prolonging antiretroviral prophylaxis during the entire breast-feeding period.