Interaction between timing of perinatal human immunodeficiency virus infection and the design of preventive and therapeutic interventions.

In 1994, the hypothesis that transmission of human immunodeficiency virus (HIV) from mother to child could be interrupted became a reality when it was shown that a regimen of zidovudine given to HIV-infected pregnant women and their newborn infants could reduce the risk of perinatal transmission by two-thirds. An understanding of the pathogenesis of transmission is crucial for interpreting these results, for design of future interventions and for understanding the natural history of perinatal HIV infection. This paper will review current information regarding the timing of and risk factors for perinatal HIV transmission, and the relationship between the timing of transmission and design of efforts to interrupt transmission and to slow disease progression in infected infants.