OBJECTIVE To estimate associations of more than minimal prenatal nicotine, alcohol, cannabis, and opioid exposures with gestational age, birth weight, and birth weight for gestational age. METHODS Data were drawn from the HEALthy Brain and Child Development (HBCD) Study, a multisite, longitudinal study in the United States. Predefined recruitment thresholds for each substance were assessed using maternal self-report, maternal toxicology results, and newborn substance exposure-related diagnoses.