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

Background: Among pregnant women with HIV (pWWH), integrated strategies of early diagnosis and treatment during pregnancy and delivery have resulted in MTCT reduction to <2%. We aim to analyse therapy changes in planning and during pregnancy and investigate pregnancy outcomes. Materials and methods: We included all pWWH enrolled in ICONA cohort in 2011–2024. Chi-squared and Wilcoxon rank-sum test were used to describe population characteristics. Changes in ART, maternal immunovirological status and MTCT were analysed. Results: Four hundred and three pregnancies in 293 pWWH were evaluated. Outcomes were available in 333 pregnancies (95 naives, 238 ART-experienced) of 262 pWWH: 38 miscarriages, 31 voluntary pregnancy interruptions and 264 full-term births (two intrauterine deaths). Characteristics of pWWH are summarized (Table 1). Seventy-one women were diagnosed with HIV while pregnant (38 first, 23 second, 10 third trimester) and started ART at median gestational (IQR) time of 15 weeks (13–21). Eleven women received diagnosis and ART post-partum. Foreign-born pWWH had the same chance of Italian-borns of being diagnosed late or after pregnancy (15/171 vs. 6/91, p = 0.54). Among the ART-experienced, 76/238 (32.0%) switched ART 6 months before pregnancy or in the first trimester: dolutegravir was interrupted in 3/101 (3%), cobicistat in 15/114 (13%) and tenofovir alafenamide in 26/195 (13%). Tenofovir disoproxil/emtricitabine remained the most common backbone in pregnancy (112/264, 42%). At delivery, a substantial proportion of pWWH received protease inhibitors (32%) and integrase strand transfer inhibitor (23%). The proportion of women achieving viral suppression by the third trimester was 84% in 2011–2015 and 93% in 2016–2024; p < 0.02. Caesarean section occurred in 57.2%, and vaginal deliveries in 32.9% (no data in 9.8%). We observed two HIV-positive newborns (0.8%): the first from a mother diagnosed late during pregnancy and starting ART shortly before delivery (29 weeks) without obtaining HIV-RNA undetectability, the second in a woman lost to follow-up during pregnancy and returned to care after delivery. Both pWWH were born outside Italy. Conclusions: HIV diagnosis occurred late during pregnancy or was missed even after delivery in 21/264 (8.0%) of pWWH, resulting in two cases of MTCT. Interventions are still needed to improve access to antenatal care and HIV testing, especially for foreign-born women.