Successful management of HIV over time demands continued engagement with the healthcare system. South Africa bears a substantial degree of HIV disease burden, with well over 7 million people living with HIV at the end of 2015. In the province of KwaZulu-Natal, approximately 40% of women enrolled in antenatal care are living with HIV, the highest prevalence of HIV among pregnant women in the world. In addition to focusing on preventing mother to child transmission (PMTCT), pregnancy is a unique time to engage women in lifelong HIV care. There are many consequences of failing to remain in HIV care postpartum. For example, women who are not retained in HIV care postpartum may or may not complete infant specific PMTCT behaviors, increasing the risk of transmitting HIV to their infant. Failing to optimize the health of mothers has the potential to lead to increased rates of HIV related orphanhood, the risks of which have been well documented and include greater risk of HIV acquisition, adverse mental health outcomes, and economic insecurity. Women not on treatment risk transmitting HIV to male partners. Lastly, opportunities to provide complementary health care (e.g., contraception) are missed. While some studies have examined adherence to postpartum PMTCT guidelines, few of these focus on continued engagement in HIV care by the mother, and very few of them examine engagement in care beyond six months postpartum. Thus, the goal of this application is to study the trajectory of women living with HIV during the postpartum period in order to identify risk factors for falling out of care, and to learn about facilitators of care that may inform subsequent intervention development. Our study will occur in two phases. In Aim 1, we will collect data from 500 women living with HIV for a period of 2 years after delivery in order to identify who is most likely to remain in or fall out of HIV care during the postpartum period. We will collect HIV RNA and self-reported contact with a health care provider every three months (visit constancy) as co-primary outcomes. Our assessment of barriers and facilitators is informed by a socio-ecological model of HIV care that has been modified based on our prior work with this population. We will then conduct individual, in-depth interviews with a subset of women and their male pregnancy partners from Aim 1 for Aim 2; (1) women who achieved suppressed HIV RNA for at least two consecutive assessments (N=12-15, based on thematic saturation), (2) women who did not achieve suppressed HIV RNA for at least two consecutive assessments (N=12-15, based on thematic saturation), and (3) women who move from suppressed HIV RNA to unsuppressed HIV RNA (or the reverse; N=12-15, based on thematic saturation). We also will interview a subset of the male partners of each of these female participants (N= 12-15 per each group). This project builds upon and existing and successful team of collaborators based in Durban, South Africa, and Boston, MA. The information learned from this project will lead to interventions to better support HIV care among postpartum women, by informing us who is most at risk for falling out of care, and on what factors intervention is needed.