Background Monitoring HIV infection rates is needed to guide health interventions and assess their impact, especially in highly vulnerable groups to the infection such as pregnant women. This study describes the trends of HIV infection over 10 years in pregnant women attending antenatal care (ANC) clinics in southern Mozambique.

Methods Data collected as part of three studies undertaken between 2010 and 2021 in HIV-infected pregnant women attending the ANC clinic were analysed. HIV incidence was estimated between prevalence points using two validated methods, one based on mortality rates and the other on survival information after HIV infection. Trends over time were obtained by fitting a second-order orthogonal polynomial regression model.

Results Overall, 10392 pregnant women attending their first ANC visit were included in the analysis. There was a decrease of the HIV prevalence from 33.9% (95% CI: 30.9–36.9%) in 2010 to 21.4% (95% CI: 19.6–23.2%) in 2021, after a peak of 35.3% (95% CI: 30.1–40.8%) in 2016. Regarding maternal age, prevalence of infection was highest in women aged 20–25 in 2010 progressively increasing in older women being the highest in 35–40 year old women in 2021. HIV infection incidence increased from 3.7 per 100 person-years during 2010–2016 to 10.1 per 100 person-years in 2018–2019, decreased to 6.2 per 100 person-years in 2020–2021.

Conclusion In the last decade, there was an initial increase of the prevalence and incidence of HIV followed by a downward trend, in this area of southern Mozambique. This encouraging trend may be attributable to the massive expansion of antiretroviral therapy during 2010–2021 in Mozambique. However, the burden HIV remains unacceptably high in this particularly vulnerable group, calling for a need to strengthen HIV preventive strategies to ending HIV/AIDs in the country.