Pregnancy and postpartum is a period of vulnerability for new or worsening psychiatric symptoms. Mindfulness Based Cognitive Therapy (MBCT) is an effective approach to mitigate pregnancy-related worsening of psychological distress. However, prior research has focused predominantly on symptoms of depression and anxiety, and is it not clear how or why MBCT improves psychological health during the perinatal period. Thus, the goals of this project are to (1) examine whether MBCT improves psychological functioning among pregnant women and whether these improvements persist at three-months postpartum, (2) examine whether improved ability to regulate emotions and behavior accounts for the beneficial effects of MBCT, and (3) determine what demographic, socioeconomic, and psychosocial factors impact treatment engagement and effectiveness.