Prospective comparison of mother-to-child transmission of HIV-1 and HIV-2 in Abidjan, Ivory Coast.

Objective: To compare mother-to-child transmission of human immunodeficiency virus types 1 and 2 (HIV-1 and HIV-2, respectively) and to assess the impact of maternal HIV-1 and HIV-2 infections on child survival.

Design: Prospective cohort study.

Setting: Maternal and child health center in a lower socioeconomic class district of Abidjan, Ivory Coast.

Participants: A total of 18,099 women delivering between 1990 and 1992 were tested for HIV-1 and HIV-2 antibodies. A cohort of 613 pregnant women and their infants was followed prospectively (138 women reactive to HIV-1, 132 reactive to HIV-2, 69 reactive to both viruses, and 274 HIV-seronegative).

Main Outcome Measures: Rates of perinatal transmission for HIV-1, HIV-2, and both viruses, determined from results of serological and polymerase chain reaction tests on children; survival of infants born to HIV-1-positive, HIV-2-positive, dually reactive, and HIV-seronegative women.

Results: Of the 18,099 women tested, 9.4% were reactive to HIV-1 alone, 1.6% to HIV-2 alone, and 1.0% to both viruses. The rate of perinatal transmission of HIV-1 was 24.7% (95% confidence interval [CI], 15.8% to 33.7%), compared with 1.2% (95% CI, 0.0% to 3.5%) for HIV-2 (relative risk, 21.3; 95% CI, 2.9 to 154.3). Overall, 19.0% (95% CI, 9.0% to 29.0%) of infants of dually reactive women became infected; of the 11 children concerned, 10 were infected with HIV-1 and one with HIV-1 and HIV-2. Infants of HIV-seropositive mothers had a reduced survival; mortality rates were 15.1, 13.0, 6.5, and 3.4 deaths per 100 child-years, respectively, for children of HIV-1-positive, dually reactive, HIV-2-positive, and HIV-seronegative women.

Conclusions: The rate of perinatal transmission of HIV-2 (1.2%) was much lower than the rate of perinatal transmission of HIV-1 (24.7%), and this was associated with more favorable survival for infants of HIV-2-infected mothers. Dually reactive women could transmit both viruses, although transmission usually involved HIV-1 only. Public health guidelines should incorporate advice that perinatal transmission of HIV-2 is rare.