The study took place at the Midwife-Obstetric Unit (MOU) at the Gugulethu Community Health Centre in Cape Town, South Africa. The MOU sees >4000 women annually for primary care antenatal, obstetric, and postpartum services. The service is operated by nurse-midwives with obstetrician support twice weekly on site and through referral to a secondary-level obstetric hospital. The local antenatal HIV prevalence is high (∼26%), and the MTCT rate is estimated at 2%–4% based on HIV-exposed infant HIV polymerase chain reaction testing at 6 weeks. PMTCT services have been offered at the Gugulethu MOU since 2001, with ART integrated into PMTCT services since 2012.