PROJECT SUMMARY The COVID-19 pandemic has had sweeping effects on pregnant women and their partners. The need to adhere to social distancing guidelines has altered the social connectedness of expectant parents, with effects on stress, loneliness, reduced access to in- person prenatal care, and childbirth support. Social support during pregnancy is known to buffer stress and predict better postpartum outcomes for both new parents and their infants. For example, greater prenatal support has been linked with decreased risk of parental postpartum mood and anxiety disorders, lower incidence of preterm birth and low birth weight, calmer infant temperament, and healthier infant development. Given this evidence, pandemic-induced changes to social connectedness during pregnancy may have long-term effects for new parents and their children. The current proposal leverages the unique natural experiment of the COVID-19 pandemic to examine the maternal and infant health effects of social connectedness among pregnant women and their partners. The CHIRP (Coronavirus, Health, Isolation and Resilience in Pregnancy) study launched in spring 2020 and has enrolled 710 expectant parents who reported on their feelings of social connectedness and support during pregnancy. We will follow up with this cohort three, six, and 12 months after the birth of their child. In addition to collecting self-report data, we will gather hospital birth charts to measure gestational outcomes, and hair cortisol to measure neuroendocrine stress exposure. We also plan to use geocoding to model the social, economic, and health impacts of the pandemic and explore how these impacts shape postpartum outcomes. Our lab has already collected data from another cohort of 200 expectant parents recruited during pregnancy and followed over the transition to parenthood, constituting a pre-pandemic comparison sample with the same measures and timing. We will also conduct a five-year follow-up with children from our pre-pandemic dataset that will incorporate behavioral and neuroimaging measures of neurodevelopment. Our pilot data indicates significantly higher ratings of psychological distress and lower ratings of social support among expectant parents affected by the COVID-19 pandemic. We expect that this project will make important contributions to the study of stress and resilience during pregnancy and its long-term effects on both maternal and infant well-being.