LATE DOSE-RESPONSE EFFECTS OF PRENATAL COCAINE EXPOSURE ON NEWBORN NEUROBEHAVIORAL PERFORMANCE

Objective. To determine in are presentative sample of full-term urban newborns of English speaking mothers whether an immediate or late dose -response effect could be demonstrated between prenatal cocaine exposu re and newborn neurobehavioral performance, controlling for confoundin g factors. Methods. The Neonatal Behavioral Assessment Scale (NBAS) wa s 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 c ocaine exposure groups were defined: heavily exposed (n = 44, >75th pe rcentile self-reported days of use during pregnancy and/or >75th perce ntile of meconium benzoylecognine concentration); lightly exposed (n = 79, less than both 75th percentiles); and unexposed (n = 101, no posi tive biological or self-report marker). At the 3-week examination ther e were 38 heavily exposed, 73 lightly exposed, and 94 unexposed infant s. Controlling for infant birth weight, gestational age, infant age at the time of examination, mothers' age, perinatal risk, obstetric medi cation, and alcohol, marijuana, and cigarette use, a regression analys is evaluated the effects of levels of cocaine exposure on NBAS perform ance. Results. No neurobehavioral effects of exposure on the newborn N BAS cluster scores or on the qualifier scores were found when confound ers were controlled for at 2 to 3 days of age. At 3 weeks, after contr olling for covariates, a significant dose effect was observed, with he avily exposed infants showing poorer state regulation and greater exci tability. Conclusions. These findings demonstrate specific dose-relate d effects of cocaine on 3-week neurobehavioral performance, particular ly for the regulation of arousal, which was not observed in the first few days of life.