The objectives of the Advancing Clinical Trials in Neonatal Opioid Withdrawal Syndrome (ACT NOW) Outcomes of Babies with Opioid Exposure (OBOE) Study are to quantify the effects of antenatal opioid exposure on the trajectory of brain development over the first 2 years of life, determine associations with developmental and neurobehavioral outcomes, and explore how specific factors (differing antenatal and postnatal exposures, severity of neonatal opioid withdrawal, maternal stress/depression/parenting) modify these effects.