Factors associated with vertical HIV transmission during two different time periods: the impact of zidovudine use on clinical practice at a Brazilian reference centre

Vertical HIV transmission rates and associated factors among mother-infant pairs cared for at a Brazilian reference centre from 1988 to 1993 (period 1), and from 1996 to 1999 (period 2) were evaluated. A total of 150 and 239 infants born to HIV+ mothers were enrolled at birth during these periods. No zidovudine prophylaxis was available in period 1. In period 2, 92.4% of the infants were exposed to zidovudine (54% started at delivery or in the post-natal period). During period 1, 25 of 129 infants were found to be infected (19.4%; 95% confidence interval [CI]=13-27) vs 20 of 232 (8.6%; 95% CI=5-13) during period 2 ( P