Adherence to antiretroviral therapy (ART) during pregnancy and the postpartum period is necessary to prevent vertical HIV transmission and to secure the long-term health of an HIV-infected woman. Health behavior theory suggests that patients’ attitudes towards medication can predict their medication-taking behaviour. This study sought to understand how women’s attitudes towards ART changes between the pregnancy and postpartum periods, and the factors associated with these attitudes. The study enrolled 200 pregnant women living with HIV. Structured surveys were administered during pregnancy and at three and 6 months postpartum. Overall, attitudes towards ART were stable over time. More positive attitudes towards ART were associated with HIV acceptance, lower levels of depression, and lower levels of shame. Counselling interventions are needed to help HIV-infected women accept their status and reduce shameful emotions. Depression screening and treatment should be integrated into PMTCT services. This study emphasizes the importance of early attention to attitudes towards ART, in order to establish a trajectory of sustained care engagement.