Because of methodological limitations, the results of the few prospective
studies assessing long-term cognitive effects of prenatal cocaine exposure
To assess effects of prenatal cocaine exposure and quality of caregiving
environment on 4-year cognitive outcomes.
Longitudinal, prospective, masked comparison cohort study from birth
(September 1994-June 1996) to 4 years.
Research laboratory of a US urban county teaching hospital.
A total of 415 consecutively enrolled infants identified from a high-risk
population screened for drug use through clinical interview, urine, and meconium
screens. Ninety-three percent retention for surviving participants at 4 years
of age resulted in 376 children (190 cocaine-exposed and 186 nonexposed).
Main Outcome Measure
The Wechsler Preschool and Primary Scales of Intelligence-Revised.
After control for covariates, prenatal cocaine exposure was not related
to lower full-scale IQ (cocaine exposed [80.7] vs nonexposed [82.9]; P = .09) scores or summary verbal (cocaine exposed [79.9]
vs nonexposed [81.9]; P = .11) or performance (cocaine
exposed [85.5] vs nonexposed [87.5]; P = .18) IQ
scores at age 4 years. However, prenatal cocaine exposure was related to small
but significant deficits on several subscales (mean [SE]): visual-spatial
skills (cocaine exposed [7.3 (0.22)] vs nonexposed [8.2 (0.22)]; P = .01), general knowledge (cocaine exposed [6.1 (0.18)] vs nonexposed
[6.7 (0.17)]; P = .04), and arithmetic skills (cocaine
exposed [6.2 (0.20)] vs nonexposed [6.8 (0.20)]; P =
.05). Prenatal cocaine exposure was also associated with a lower likelihood
of achievement of IQ above normative means (odds ratio, 0.26 [95% confidence
interval, 0.10-0.65]; P = .004). The quality of the
caregiving environment was the strongest independent predictor of outcomes.
Cocaine-exposed children placed in nonrelative foster or adoptive care lived
in homes with more stimulating environments and had caregivers with better
vocabulary scores, and they attained full-scale and performance IQ scores
(83 and 87, respectively) similar to nonexposed children in biological maternal
or relative care (full-scale IQ, 82; performance IQ, 88) and higher than cocaine-exposed
children in biological maternal or relative care (full-scale IQ, 79; performance
Prenatal cocaine exposure was not associated with lower full-scale,
verbal, or performance IQ scores but was associated with an increased risk
for specific cognitive impairments and lower likelihood of IQ above the normative
mean at 4 years. A better home environment was associated with IQ scores for
cocaine-exposed children that are similar to scores in nonexposed children.