1 in 5 parents experience perinatal distress (PND), significant mental health challenges that impact their – and their children’s and families’ – lives and wellbeing. While perinatal mood and anxiety disorders (PMADs) have received increasing attention, more research on perinatal OCD (pOCD) is needed. Although symptoms vary from person to person, individuals with pOCD often have highly distressing thoughts surrounding the safety and wellness of their children, and engage in compulsive behaviors to try to reduce the resulting distress. Individual differences in how PND is experienced pose a major obstacle to understanding, preventing, and treating pOCD effectively. Ambulatory assessment (AA) may offer novel opportunities to examine individual pOCD experiences in real-world settings, but no studies have used AA to examine pPOCD. This study aims to address this research gap by using smartphone-based longitudinal AA to assess 66 pregnant individuals at high risk for PND during late pregnancy and the first postpartum months. By looking at associations among symptoms and relevant events and feelings in real time, this study will probe into the individual differences, onset, and progression of pOCD presentations. Through the context-aware, time-sensitive, and person-specific inferences about pOCD, this research into AA can inform future personalized interventions for parents at a critical stage.