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OBJECTIVE: To evaluate how maternal and obstetric factors interact to influence mother-to-child human immunodeficiency virus type 1 (HIV-1) transmission. DESIGN: Prospective, observational cohort study of children born to HIV-infected women to determine child's HIV infection status. The analysis then compared peripartum maternal, placental, and obstetric variables between HIV-1 transmitter and nontransmitter women. SETTING: Two large maternity wards in Kinshasa, Zaire. PARTICIPANTS: Consecutive sample of 324 HIV-1-infected women at delivery, with 254 HIV-seronegative women followed up as control subjects. PRINCIPAL OUTCOME MEASURES: HIV infection status of children, to classify each woman as an HIV-1 transmitter or nontransmitter. RESULTS: The highest transmission risk (TR) was associated with maternal p24 antigenemia (TR, 71%; relative risk RR, 3.0; 95% confidence interval CI, 1.7 to 5.2) and maternal CD8+ lymphocyte counts of at least 1.80 x 10(9)/L (1800/microL) (TR, 50%; RR, 2.2; 95% CI, 1.2 to 4.2). Among women with CD8+ lymphocyte counts of less than 1.80 x 10(9)/L, CD4+ lymphocyte counts of less than 0.60 x 10(9)/L were a risk factor (TR, 29%; RR, 2.2; 95% CI, 1.2 to 4.2). In women with neither high CD8+ nor low CD4+ lymphocyte counts, placental membrane inflammation was associated with perinatal transmission (TR, 40%; RR, 4.2; 95% CI, 1.3 to 13.7). In women with neither p24 antigenemia, high CD8+ or low CD4+ lymphocyte counts, nor placental membrane inflammation, the transmission risk was only 7%. Additional correlates of transmission included maternal anemia and fever, but not maternal sexually transmitted diseases. CONCLUSIONS: Identifiable subgroups of HIV-1-infected women based on maternal and placental characteristics had between a 7% and 71% risk of perinatal HIV-1 transmission. Not only the overall rate of transmission but the impact of different risk factors for transmission appear to vary over the course of HIV infection.
Michael E. St. Louis (Wed,) studied this question.