Brain health Begins Before Birth (B4): A "learning" pregnancy and birth cohort study.

Mental health disorders affect over 1 billion people worldwide, profoundly impacting individuals, families, and the global economy. Risk for psychopathology begins early in life, with the perinatal period representing a critical window of vulnerability. The Brain health Begins Before Birth (B4) Study at Massachusetts General Hospital (MGH) is a prospective birth cohort designed to identify modifiable risk and resilience factors influencing early brain development and child- and adult-onset psychopathology. This study aims to deeply phenotype prenatal exposures through maternal surveys administered at multiple time points during and after pregnancy; assess early neurodevelopmental outcomes through the first two years of life; and triangulate exposure and outcome data with underlying biological mechanisms. The B4 Study consists of structured, remote surveys covering psychosocial, environmental, and health-related factors throughout pregnancy and the first two years of life, supplemented by medical record review. By integrating risk and resilience factors into a dynamic learning cohort model, the B4 Study aims to advance the field of preventive psychiatry by identifying actionable pathways for early intervention, testing strategies in real-time, and ultimately shaping policies that promote lifelong mental health and wellbeing from the earliest stages of development.