Neurodevelopment of adopted children exposed in utero to cocaine: The Toronto Adoption Study

Background: Published studies of children's neurodevelopment after in utero exposure to cocaine have not separated intrauterine from postnatal environmental effects as cocaine-using mothers cluster in low socioeconomic classes and have other risk factors. Methods: To overcome this limitation, a study was done to assess physical and neurodevelopmental characteristics of 52 children: 26 were adopted by parents who sought counselling in the Motherisk Program at the University of Toronto for prenatal cocaine exposure, and 26 were controls matched for maternal intelligence quotient (IQ), socioeconomic status and gestational age. Main outcome measures: Head circumference, McCarthy General Cognitive Index (GCI) score, language performance and temperament tests. Results: The children in the study group had smaller head circumferences (34th versus 54th percentiles p = 0.009), lower McCarthy GCI scores (102.8 versus 114.2, p = 0.02), poorer receptive and expressive language performance on the Reynell test, and higher activity levels, less persistence and increased distractibility on temperament tests. On multivariate analysis, cocaine exposure was significantly (p = 0.001) associated with lower IQ and poorer language development independent of intrauterine growth retardation and other potential confounders. Interpretation: By controlling for postnatal environmental factors, this adoption study documents intrauterine developmental risks associated with cocaine exposure. Follow-up into school years is warranted to evaluate the extent of these effects.