Adherence to option B+ antiretroviral treatment and associated factors during pregnancy and postpartum in a South Africa clinical setting - In some regions, HIV prevalence is among the highest in the world, with up to 40% of pregnant women infected with HIV.1 The prevention of vertical transmission of HIV from mother to child (PMTCT) requires women to consistently take lifelong ART medication, known as Option B+, to achieve viral suppression and prevent transmission. However, antiretroviral treatment (ART) often declines during the postpartum period, contributing to a higher proportion of pediatric HIV infections occurring within the first two months of life.2 Globally, an estimated 27% of women have experienced intimate partner violence (IPV), with rates even higher in some high-prevalence settings.3 Pregnant and postpartum women (e.g., perinatal) living with HIV and experiencing IPV are associated with poorer ART adherence, lower viral suppression, higher mortality, and impediments in regular engagement in clinical care.4 Despite compelling research indicating that the postpartum period is particularly vulnerable to declines in ART adherence and despite an increase in pediatric HIV serovoncersions,5 many studies rely primarily on self-reported adherence measures and less often assess the transition from pregnancy to postpartum using objective adherence measures.6-7 Moreover, the integration of qualitative findings that contextualize the challenges during the postpartum phase are often limited in the literature.8-9 The objective of this study is to examine the social and behavioral mechanisms through which IPV may alter ART adherence among perinatal women living with HIV. The specific aims of this study are to: (1) Contextualize HIV antiretroviral treatment adherence and constraints in the postpartum period qualitatively by exploring how and why violence alters ART adherence; (2) Use mixed methods research to examine multiple measures of ART adherence over the perinatal phase to determine factors associated with non-adherence; and (3) Investigate the association between IPV in pregnancy and perinatal viral load suppression versus non-viral suppression. The proposed study will utilize data from a prospective cohort parent study involving 225 perinatal women living with HIV engaging in care across two antenatal care clinics in a high-prevalence area. This mixed methods design, employing qualitative and quantitative data sources, aims to inform perinatal ART adherence by providing insight into the social and behavioral factors altering ART adherence postpartum. To my knowledge, this is the first study to assess the dynamics of antiretroviral adherence both qualitatively and quantitatively during pregnancy and up to 15 months postpartum, using biological markers (hair samples) and viral load data, complemented by qualitative exploration of ART adherence. The findings will address a critical gap in the HIV treatment literature by advancing our understanding of the social and behavioral factors influencing sub-optimal postpartum ART adherence. Existing interventions strongly support the need for this proposed research.