Objective. To evaluate the direct effects of prenatal cocaine exposure and prenatal opiate exposure on infant mental, motor, and behavioral outcomes longitudinally between 1 and 3 years old.

Methods. As part of a prospective, longitudinal, multisite study, the Bayley Scales of Infant Development II were administered to 1227 infants who were exposed to cocaine (n = 474), opiates (n = 50), cocaine and opiates (n = 48), and neither substance (n = 655) at 1, 2, and 3 years of corrected age by certified, masked examiners. Hierarchic linear modeling of the 1-, 2-, and 3-year scores was conducted using cocaine and opiate exposure as predictors with and without controlling for covariates.

Results. Overall retention was 88.4% and did not differ by cocaine or opiate exposure. Overall (at 1, 2, and 3 years), cocaine-exposed infants scored 1.6 Mental Development Index points below infants who were not exposed to cocaine. Opiate-exposed infants scored 3.8 Psychomotor Development Index points below infants who were not exposed to opiates. Neither the cocaine nor the opiate effect remained significant after controlling for covariates. Neither cocaine nor opiate exposure was associated with the Behavioral Record Score during the examination. Low birth weight and indices of nonoptimal caregiving were associated with lower Mental Development Index, Psychomotor Development Index, and Behavioral Record Score scores for all groups of infants.

Conclusions. In the largest at-risk sample observed longitudinally to date, infant prenatal exposure to cocaine and to opiates was not associated with mental, motor, or behavioral deficits after controlling for birth weight and environmental risks.

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