Syphilis in pregnant women living with HIV/AIDS in Brazil and the relationship between coinfection and mother-to-child transmission of HIV

Background HIV and syphilis are sexually transmitted infections of concern during pregnancy that affect women and children globally. However, limited data is available regarding the prevalence of syphilis infection among pregnant women living with HIV/AIDS and its influence on mother‒to-child transmission (MTCT) of HIV. The present research aims to analyze HIV and syphilis coinfection during pregnancy through a national analysis of surveillance data from Brazil. Methods This retrospective cohort study used secondary data from the Ministry of Health's information systems. The data included reported cases of pregnant women living with HIV and syphilis, with childbirth between 2016 and 2020, and children with HIV/AIDS with a year of birth from 2016–2020. Cross-referencing was performed between notification databases of pregnant women with HIV/AIDS and syphilis and pregnant women with HIV/AIDS and children with HIV/AIDS to identify potential mother‒child pairs. Pregnant women without a paired child with HIV were considered to have no outcome of MTCT for HIV. Logistic regression analysis was performed to estimate the effect of HIV and syphilis coinfection during pregnancy and HIV-MTCT, with a final significance level of 5%. Results Among 40,634 pregnant women living with HIV, 2,788 were coinfected with syphilis, yielding a coinfection rate of 6.9%. The MTCT of HIV was significantly greater among HIV-positive pregnant women coinfected with syphilis (2%) than among those without coinfection (1.2%), with an odds ratio of 1.7 (95% CI 1.29–2.25, p ≤ 0.05). Coinfection with HIV and syphilis was more prevalent among young women (aged 10–24), non-white individuals and people with lower educational attainment, and those who did not receive prenatal care and had late laboratory evidence of HIV during pregnancy, indicating a more vulnerable population among the coinfected pregnant women. Conclusions Compared with HIV-positive pregnant women without syphilis, HIV coinfection with syphilis during pregnancy was associated with a higher MTCT rate of HIV. Intersectoral public policies addressing social determinants are essential to achieve the goals of eliminating MTCT.