HIV-1 INFECTION IN A POPULATION-BASED TWIN SAMPLE

Objective: To examine factors associated with perinatal HIV-1 transmis sion among twins. Methods: We identified twins delivered by a populati on-based cohort of HIV-infected mothers on New York State Medicaid. Te sted algorithms were applied to Medicaid files to identify HIV infecti on in mothers and twins. The HIV transmission rate 3 years after deliv ery was assessed from Kaplan-Meier curves. Proportional hazards models with adjustment for twin clustering were used to determine the relati ve hazard (RH) of transmission. Results: In 35 twin pairs, transmissio n was 20.5%. The risk of transmission was increased significantly for advanced maternal HIV infection (rh = 10.8, 95% confidence interval 2. 11, 54.9). We found no association of birth order with twin HIV status . Conclusions: These data suggest that maternal stage of disease plays a greater role in vertical HIV transmission than birth order. To prev ent material-child HIV transmission, reducing maternal viral load is l ikely to have a greater impact than modifying delivery factors.