Late or missed HIV diagnosis during pregnancy is still occurring in a high-income country and represents a high risk of MTCT

Background: Integrated strategies for early HIV diagnosis and treatment among pregnant women with HIV (pWWH) have reduced mother-to-child transmission (MTCT) to below 2%. We aim to evaluate pregnancy outcomes and antiretroviral therapy (ART) changes in pWWH during pregnancy planning and delivery. Materials and methods: We included pWWH enrolled in the ICONA Cohort in 2011-2024. Wilcoxon rank-sum and Chi-squared or Fisher's exact tests described population characteristics. ART modifications, maternal immunovirological status, and MTCT rates were analysed. Multivariable regression analysis assessed the likelihood of viral suppression at delivery. Results: 419 pregnancies in 311 pWWH were evaluated; outcomes were available for 333 pregnancies (100 ART-naive, 233 ART-experienced) in 255 pWWH: 267 live-born births (80%), 35 miscarriages, 28 voluntary interruptions, 2 stillbirths, and 1 intrauterine death. HIV was diagnosed during pregnancy in 83 women. ART changes occurred in 29.6% of ART-naïve during pregnancy. Among ART-experienced, 6% changed in the six months before pregnancy, 25.8% during the first trimester, and 4.7% afterward. Tenofovir disoproxil/emtricitabine was the most used backbone. A significant proportion of pregnancies were exposed to PIs, but use of INSTIs increased over time. Caesarean section occurred in 44.4%, vaginal deliveries in 24.9%. Two HIV-positive newborns were observed (1.1%). Conclusions: Despite improved viral suppression, late or missed HIV diagnoses during pregnancy continue to drive MTCT. Strengthening early HIV testing, antenatal care access, and retention in care is critical to eliminate perinatal transmission.