PrEP is safe and effective but requires adherence during potential HIV exposure, yet the facilitators of long-term maternal adherence are not well understood. We conducted semi-structured interviews with 25 postpartum women who reported high adherence (PrEP use ≥ 25 days in last 30-days and never missed a PrEP prescription in pregnancy/postpartum period) within a PrEP service for pregnant and postpartum women. A thematic approach guided an iterative process of coding and analysis. Themes identified as drivers of optimal PrEP use were HIV risk perception, mainly because of partner's behaviors and unknown serostatus, and a strong desire to have a baby free of HIV. Reported disclosure of PrEP use facilitated PrEP adherence. Women discussed having partner and family support, which included reminders to take PrEP daily. Primary barriers were anticipated or experienced stigma, overcome through education of partners and family about PrEP. Pregnant women experienced transient side-effects, but found ways to continue, including taking PrEP at night. PrEP programs for pregnant and postpartum women should integrate strategies to assist women with realistic appraisals of risk and teach skills for disclosure and securing support from significant others.