This case-control study aimed to identify maternal sociodemographic, behavioral, and care-related factors associated with mother-to-child transmission (MTCT) of HIV in Porto Alegre, capital of Rio Grande do Sul, the southernmost state of Brazil. Was used secondary data from the epidemiological surveillance of mothers and children exposed to HIV through pregnancy/delivery born from 2010 to 2015. For each case of HIV MTCT, 4 controls without HIV MTCT were randomized, matched for year of birth and maternal age. Multivariate logistic regression analysis used a backward model and a theoretical hierarchical model. The sample consisted of 75 cases and 300 controls. There was a linear trend toward an increasing likelihood of HIV MTCT with decreasing levels of education, with a strong association with no schooling (OR 18.57; 95%CI: 3.19-108.23). Care-related variables were associated with HIV MTCT in all analyses. The likelihood of HIV MTCT increased when HIV was diagnosed at delivery compared with HIV diagnosis before pregnancy. In conclusion, HIV MTCT was more likely to occur in mothers who did not receive prenatal care, did not use ARVs, and had a higher number of HIV-positive pregnancies. This reinforces the importance of the health system in the prevention of HIV MTCT.

Keywords: Vertical infectious disease transmission; HIV; case-control studies.