Common mental disorders (CMD) of depression and anxiety are prevalent and largely untreated among Kenyan pregnant and postpartum women living with HIV (PPWH). CMD lead to poor maternal and child health outcomes and contribute to lack of HIV care engagement and virologic failure in PPWH. While efficacious treatments for CMD exist, scaling treatment within routine health care in low- and middle-income (LMIC) settings will require stakeholder engagement and both effectiveness and implementation data to inform scale up and sustainability. The study team has integrated other efficacious interventions into antenatal (ANC) and HIV care in Kenya. The investigators now propose to integrate proven mental health services using a collaborative care model, combined with a low intensity evidence-based intervention (problem solving therapy), while targeting known social determinants of HIV-related health for PPWH (stigma and IPV). Building on the current multidisciplinary approach for HIV care in Kenya, the proposed Collaborative Care Model (CCM) will utilize existing peer mentor mothers, non-specialist behavioral care managers, and psychiatric nurses; and will incorporate a consultant psychiatrist into the ANC/HIV care team. Guided by the EPIS (Exploration-Preparation-Implementation-Sustainment) framework, the overall study goal is to integrate collaborative care for perinatal CMD within routine ANC/HIV services in Kenya, assess the costs and cost-effectiveness of this approach, and work with policy and decision makers to determine key considerations for scale-up. Specifically, in Aim 1, the investigators will identify contextual barriers and facilitators to refine an optimal integration model for delivering collaborative care model using multimethod data collection (focus groups with providers, in-depth interviews with key informants, and a clinic readiness checklist). A workshop with the study Advisory Board comprising of both county and national level stakeholders, will allow investigators to translate findings into a locally relevant CCM. In Aim 2, the investigators will test CCM in antenatal care for PPWH in a hybrid type 2 implementation-effectiveness trial using a stepped wedge design at 15 primary health care facilities in southwestern Kenya. The investigators will introduce CCM care for PPWH diagnosed with CMD during antenatal care. The co-primary health outcomes at 12 months postpartum will be (1) recovery from depression or anxiety symptoms in PPWH, and (2) proportion PPWH with sustained viral suppression and retention in HIV care. Key implementation outcomes are feasibility and acceptability. Finally, in Aim 3, the investigators will refine CCM implementation strategies through cost-effectiveness and dissemination research. The investigators will carry out costing and cost-effectiveness analysis and invite policy and decision-makers to participate in a nominal group technique process to elucidate factors for further scale up and sustainment of the CCM approach. Findings from this study will guide the development of a scalable model adaptable to other LMIC settings, contributing to global HIV and maternal health goals while addressing the burden of untreated CMD.