BACKGROUND: Emotion dysregulation is a transdiagnostic correlate of psychopathology. However, longitudinal changes in emotion dysregulation have been understudied during the transition to parenthood. Additionally, less is known about whether prenatal and birth experiences may be associated with changes in emotion dysregulation across time. METHODS: Data were collected from a longitudinal study of 385 pregnant individuals from their third trimester through to 18 months postpartum. Participants self-reported their emotion dysregulation at their prenatal visit, birth, 7 months, and 18 months postpartum. Additionally, participants reported on prenatal life stress, pregnancy-related hassles, and childbirth experiences through self-report measures and a semi-structured interview. RESULTS: Results show non-linear decreases in emotion dysregulation from pregnancy to 18 months postpartum. On average, there was a significant decrease in self-reported emotion dysregulation from pregnancy to birth, followed by rank stability higher from birth through 18 months postpartum. More stress during pregnancy was associated with levels of emotion dysregulation and birth experiences characterized by fear were associated with more stability in emotion dysregulation from pregnancy to birth. LIMITATIONS: We only assessed emotion dysregulation once prenatally, so our findings do not account for changes across pregnancy. Additionally, our measures are all self-report through questionnaires and a semi-structured interview. CONCLUSIONS: Our study is consistent with literature on trajectories of psychopathology across the perinatal period. Assessing emotion dysregulation can help identify those at higher risk for psychopathology during the transition to parenthood. Our findings highlight the importance of prenatal and birth experiences, and the need to support mental health during this sensitive period.