Factors Predictive of Maternal-Fetal Transmission of HIV-1: Preliminary Analysis of Zidovudine Given During Pregnancy and/or Delivery

Objective. —To assess maternal risk factors potentially influencing vertical transmission of human immunodeficiency virus, type 1 (HIV-1), including maternal CD4 cell count; presence of immune complex dissociated (ICD) p24 antigen; maternal zidovudine therapy during pregnancy and/or delivery; complications of pregnancy, such as preterm labor and birth; and obstetric events during labor and delivery, such as duration of labor, mode of delivery, chorioamnionitis, and maternal blood exposure. Design and Setting. —A nonrandomized prospective cohort study at a university medical center and two general hospital affiliates. Patients. —Sixty-three HIV-1—seropositive pregnant women and their 68 infants. Intervention. —Twenty-six mothers received zidovudine therapy during pregnancy and/or during labor and delivery. Main Outcome Measure. —HIV-1 infection status of the infant. Results. —Thirteen of the 68 infants were vertically infected with HIV-1. Mothers with events involving fetal exposure to maternal blood were more likely to transmit infection (four [31%] of 13 vs three [5%] of 55, P =.02), as were women with plasma ICD p24 antigenemia at delivery (six [67%] of nine vs 11 [25%] of 44, P =.02). Zidovudine treatment was associated with a significant reduction in vertical transmission (one [4%] of 26 mothers treated with zidovudine vs 12 [29%] of 42 mothers not treated with zidovudine, P =.01). There was a significant protective effect of zidovudine treatment despite lower mean absolute CD4 cell counts (0.37×10 9 /L) in the 24 zidovudine-treated nontransmitters and in the nine non—zidovudine-treated transmitters (0.37×10 9 /L) than in the 24 non—zidovudine-treated nontransmitters (0.62×10 9 /L) ( P =.008). Conclusion. —Maternal-fetal HIV-1 transmission is multifactorial, with increased risk associated both with ICD p24 antigenemia at term and with intrapartum events that increase fetal exposure to maternal blood. Zidovudine therapy given during pregnancy and/or labor and delivery was associated with a significant reduction in vertical transmission. These data suggest that the beneficial effects of zidovudine therapy in reducing maternal-fetal HIV-1 transmission recently found in protocol 076 of the placebo-controlled Acquired Immunodeficiency Syndrome Clinical Trials Group Study may extend to women with lower CD4 cell counts and suggest that prolonged treatment of infants may not be necessary. ( JAMA . 1994;271:1925-1930)