Distinct risk factors for intrauterine and intrapartum human immunodeficiency virus transmission and consequences for disease progression in infectedchildren

Predictors and prognosis of intrauterine and intrapartum human immunodefici ency virus (HIV) transmission were investigated among 432 children of HIV-i nfected women in the Perinatal AIDS Collaborative Transmission Study. Timin g of transmission was inferred from polymerase chain reaction or viral cult ure within 2 days of birth, Proportions of infections due to intrauterine t ransmission were similar among women using (29%) or not using zidovudine (3 0%). Preterm delivery was strongly associated with intrapartum transmission (relative risk, 3.7; 95% confidence interval [CI], 2.2-6.1), particularly among infants delivered longer after membrane rupture, but was not associat ed with intrauterine transmission, Progression to AIDS or death increased 2 .5-fold (95% CI, 1.1-5.8) among intrauterine infected children, adjusting f or preterm delivery, and maternal CD4 cell count, Early transmission appear s unlikely to explain instances of zidovudine failure. Preterm infants may be more vulnerable to HIV acquisition at delivery, especially if membrane r upture is prolonged. Intrauterine infection does not appear to increase ris k of preterm delivery.