Objective: To determine in a representative sample of full-term urban newborns of English-speaking mothers whether an immediate or late dose-response effect could be demonstrated between prenatal cocaine exposure and newborn neurobehavioral performance, controlling for confounding factors.
Methods: The Neonatal Behavioral Assessment Scale (NBAS) was administered by masked examiners to a total sample of 251 clinically healthy, full-term infants at 2 days and/or 17 days. Three in utero cocaine exposure groups were defined: heavily exposed (n = 44, > 75th percentile self-reported days of use during pregnancy and/or > 75th percentile of meconium benzoylecognine concentration); lightly exposed (n = 79, less than both 75th percentiles); and unexposed (n = 101, no positive biological or self-report marker). At the 3-week examination there were 38 heavily exposed, 73 lightly exposed, and 94 unexposed infants. Controlling for infant birth weight, gestational age, infant age at the time of examination, mothers' age, perinatal risk, obstetric medication, and alcohol, marijuana, and cigarette use, a regression analysis evaluated the effects of levels of cocaine exposure on NBAS performance.
Results: No neurobehavioral effects of exposure on the newborn NBAS cluster scores or on the qualifier scores were found when confounders were controlled for at 2 to 3 days of age. At 3 weeks, after controlling for covariates, a significant dose effect was observed, with heavily exposed infants showing poorer state regulation and greater excitability.
Conclusions: These findings demonstrate specific dose-related effects of cocaine on 3-week neurobehavioral performance, particularly for the regulation of arousal, which was not observed in the first few days of life.