Objective: To determine the rate and factors associated with perinatal transmission among women infected with HIV-1.
Design: Cohort study.
Setting: Centro Municipal de Atendimento em DST/AIDS is a major reference centre for HIV treatment in Porto Alegre city, southern Brazil.
Population: Pregnant and puerperal women infected with HIV-1.
Methods: Women were enrolled during pregnancy and seen monthly at the antenatal care centre. Those detected at delivery that presented at the centre within the first 10 days of postpartum were included. Maternal, obstetric and infant-related characteristics were ascertained and testing for CD4 cell count, HIV PCR/RNA assay, anti-HCV, HBSAg and syphilis were performed. Antiretrovirals and formula were provided free of charge following Brazilian guidelines.
Main outcome measure: HIV-1 infection status in the infant.
Results: Perinatal transmission was assessed in 343 children (95% of the whole sample). Overall, the transmission rate was 3.2% (95% CI: 1.7-5.8%). Perinatal transmission rates increased with maternal viral load (>/=10,000 copies/mL; RR: 11.27; 95% CI: 1.38-92.23). In multivariate analyses, the only independent risk factor for perinatal transmission was the maternal viral load at baseline (OR = 2.72 per log increase in the number of copies; 95% CI: 1.17-6.50).
Conclusion: Perinatal transmission rate was low among HIV-1 infected women in clinical care and on antiretroviral therapy despite poor socio-economic conditions. Viral load level was the only independent predictor of perinatal transmission. It is possible to prevent HIV-1 perinatal transmission in a developing country if we provide antiretrovirals and formula.