Mentor Mothers (MMs) are peer supporters who help pregnant and postpartum women living with HIV (WLHIV) as they receive prevention of mother-to-child transmission of HIV (PMTCT) services in resource-limited settings like Kenya. Differentiated service delivery (DSD) is a care model that tailors services based on clients' needs, helping to improve both the quality and efficiency of care. This hybrid implementation-effectiveness study will test whether an enhanced MM strategy that uses DSD can be successfully carried out and improve health outcomes for mothers and infants. The study will take place at Burnt Forest Sub-District Hospital (BFSDH) in Kenya. Researchers will ask: * Can the enhanced MM strategy be delivered as planned and accepted by patients and staff? * Does the strategy improve clinical outcomes like keeping mothers in PMTCT care, achieving HIV viral suppression, completing infant HIV testing, and preventing HIV transmission to infants? Researchers will compare health outcomes before and after the strategy is introduced at BFSDH, and also compare outcomes at other similar clinics that continue with standard MM services. Women who choose to participate will meet with a MM during their routine antenatal and postnatal clinic visits. They will be offered the enhanced MM support, but can choose to receive standard care if they prefer.