To examine HIV care attrition patterns and risk factors among adolescent girls and young women (AGYW) enrolled in prevention of mother-to-child transmission of HIV (PMTCT) services in Tanzania.

Prospective cohort study.

The study was conducted in three regions of Tanzania: Kagera, Tabora and Dar es Salaam across 543 public and private health facilities.

A total of 10 147 pregnant and postpartum AGYW living with HIV attending PMTCT services between 1 January 2018 and 31 December 2020 were included in this study and followed prospectively until they were censored at the last appointment date or 31 December 2023, whichever was earlier.

The primary outcome was time to HIV care attrition, defined as death, discontinuation of antiretroviral treatment (ART) or loss to follow-up (LTFU). LTFU was defined as failure to attend a scheduled clinic appointment and being absent from care for ≥90 consecutive days following a missed appointment among non-transfers. Kaplan-Meier analyses were used to estimate time to first attrition. The Anderson-Gill proportional hazard model estimated the risk factors for repeated care interruptions, adjusted for baseline characteristics and stratified by ART status at PMTCT enrolment.

A total of 3259 attrition events were observed, of which 79% occurred within the first year, with the median time to first attrition of 4 months (IQR: 1–8), 96.3% were due to LTFU. Over two-thirds of first-year attrition occurred among AGYW newly started on ART at PMTCT enrolment, who had more than twice the attrition rate of those already on ART (28.6 vs 11.2 per 100-person-years). Of AGYW lost to follow-up, 44.8% returned to care and 20.9% experienced subsequent attrition. Among AGYW new on ART, attrition was higher in those enrolled late in their third trimester (adjusted HR (aHR) 1.20; 95% CI 1.01 to 1.42) versus those in the first trimester and lower during the postpartum period (aHR 0.58; 95% CI 0.43 to 0.79). In AGYW already on ART, attrition rate was higher among adolescents 18–19 years (aHR 1.37; 95% CI 1.13 to 1.66) and those enrolled late; during the second (aHR 1.41; 95% CI 1.16 to 1.72) and third trimesters (aHR 1.57; 95% CI 1.23 to 2.00) or post partum (aHR 1.36; 95% CI 1.09 to 1.70) compared with the first trimester. AGYW with early-stage HIV, on second-line regimens and attending facilities with fewer AGYW, had a lower attrition rate in contrast to comparison groups.

AGYW newly started on ART at PMTCT enrolment are more likely to have early and recurring dropout. Given the cyclical nature of HIV care engagement, tailored and repeated interventions are needed to support continuous retention and re-engagement for pregnant and postpartum AGYW with HIV.