Abstract Perinatal care continuity across the full continuum is essential for optimizing maternal and infant health; however, a stark gap occurs postpartum, with less than one half of Indian mothers receiving postpartum care due to significant logistical and sociocultural barriers, particularly for peri-urban and rural residents. To overcome these barriers and reduce women’s postpartum isolation, our international team of maternal and infant health clinicians and researchers developed and pilot-tested a culturally-tailored mobile interactive education and support group intervention: Maa Shishu Swasthya Sahayak Samooh (maternal and child health support group: MeSSSSage). MeSSSSage uses a provider-moderated group approach to increase women’s communication with providers, refer to in-person care, and connect them with a virtual social support group. Participants are recruited in late pregnancy and have 26 education and support sessions via audioconference facilitated by nurse-midwives (2 prenatal and weekly postpartum sessions through 6 months), plus engage in a text chat group. Pilot results indicated high acceptability and feasibility and suggest preliminary effectiveness. We propose to test the effectiveness of the MeSSSSage intervention compared to standard care on maternal and neonatal health-related behaviors and health outcomes in a randomized controlled trial among 2100 perinatal Indian women. Primary outcomes of exclusive breastfeeding, unmet need for postpartum contraceptives and postpartum depression will be assessed at 6 months. Our specific aims are to: estimate the effectiveness of a mobile interactive education and support group intervention (MeSSSSage) on postpartum behaviors for optimizing maternal and neonatal health in India (Aim 1), characterize the mechanisms of impact of the MeSSSSage intervention on maternal and neonatal health in India (Aim 2), and determine the cost-effectiveness of the MeSSSSage intervention in improving postpartum maternal and neonatal health as compared to the standard of care. We hope to positively impact women’s postnatal health knowledge and behaviors and improve health outcomes for women and their infants in the first six months postpartum. This study of a scaleable intervention will have an important contribution to the evidence base on mHealth for maternal and perinatal health and group care models for postnatal care, contributing to reducing disparities in women’s access to care through the removal of geographic and social barriers. 1