Infant Behaviors, Prenatal Cocaine Exposure, and Adult Intelligence.

Importance: Linking prenatal drug exposures to both infant behavior and adult cognitive outcomes may improve early interventions.

Objective: To assess whether neonatal physical, neurobehavioral, and infant cognitive measures mediate the association between prenatal cocaine exposure (PCE) and adult perceptual reasoning IQ.

Design, Setting, And Participants: This study used data from a longitudinal, prospective birth cohort study with follow-up from 1994 to 2018 until offspring were 21 years post partum. A total of 384 (196 PCE and 188 not exposed to cocaine [NCE]) infants and mothers were screened for cocaine or polydrug use. Structural equation modeling was performed from June to November 2023.

Exposures: Prenatal exposures to cocaine, alcohol, marijuana, and tobacco assessed through urine and meconium analyses and maternal self-report.

Main Outcomes And Measures: Head circumference, neurobehavioral assessment, Bayley Scales of Infant Development, Fagan Test of Infant Intelligence score, Wechsler Perceptual Reasoning IQ, Home Observation for Measurement of the Environment (HOME) score, and blood lead level.

Results: Among the 384 mothers in the study, the mean (SD) age at delivery was 27.7 (5.3) years (range, 18-41 years), 375 of 383 received public assistance (97.9%) and 336 were unmarried (87.5%). Birth head circumference (standardized estimate for specific path association, -0.05, SE = 0.02; P = .02) and 1-year Bayley Mental Development Index (MDI) (standardized estimate for total of the specific path association, -0.05, SE = 0.02; P = .03) mediated the association of PCE with Wechsler Perceptual Reasoning IQ, controlling for HOME score and other substance exposures. Abnormal results on the neurobehavioral assessment were associated with birth head circumference (β = -0.20, SE = 0.08; P = .01). Bayley Psychomotor Index (β = 0.39, SE = 0.05; P < .001) and Fagan Test of Infant Intelligence score (β = 0.16, SE = 0.06; P = .01) at 6.5 months correlated with MDI at 12 months.

Conclusions And Relevance: In this cohort study, a negative association of PCE with adult perceptual reasoning IQ was mediated by early physical and behavioral differences, after controlling for other drug and environmental factors. Development of infant behavioral assessments to identify sequelae of prenatal teratogens early in life may improve long-term outcomes and public health awareness.