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Dose-response effect of fetal cocaine exposure on newborn neurologic function
C A Chiriboga1, J C Brust, D Bateman
1Division of Pediatric Neurology, Department of Neurology, College of Physicians and Surgeons, Columbia University, New York, USA.
Background:
Studies of fetal cocaine exposure and newborn neurologic function have obtained conflicting results. Although some studies identify abnormalities, others find no differences between cocaine-exposed and cocaine-unexposed infants. To determine the effects of prenatal cocaine exposure on intrauterine growth and neurologic function in infants, we prospectively evaluated 253 infants shortly after birth.
Methods:
Women who delivered a live singleton >36 weeks by dates were eligible for enrollment. Maternal exclusionary criteria were known parenteral drug use, alcoholism, and acquired immunodeficiency syndrome; infant exclusionary criteria were Apgar scores
Results:
Compared with unexposed controls, cocaine-exposed infants exhibited higher rates of intrauterine growth retardation (24% vs 8%), small head circumference ([HC] <10th% percentile) (20% vs 5%) and neurologic abnormalities: global hypertonia (32% vs 11%), coarse tremor (40% vs 15%), and extensor leg posture (20% vs 4%). We found increasing odds (odds ratio) of growth and neurologic impairment with increasing level of cocaine exposure in stratified analyses. The odds ratio associated with three levels of cocaine exposure (no exposure, low exposure = RIAH 2-66 ng/mg; and high exposure = RIAH 81-4457 ng/mg) respectively are: 1.0, 3.3, and 6.1 for small head size (chi2 for trend); 1.0, 3. 3, and 4.3 for global hypertonia (chi2 for trend); 1.0, 3.4, and 7.4 for extensor leg posturing (chi2 for trend); and 1.0, 3.8, and 3.8 for coarse tremor (chi2 for trend). Significant associations between cocaine exposure and neurologic signs were found in logistic regression equations that controlled for 20 or more variables.
Conclusion:
We conclude that adverse neonatal effects associated with fetal cocaine exposure follow a dose-response relationship: newborns with higher levels of prenatal cocaine exposure show higher rates of impairments in fetal head growth and abnormalities of muscle tone, movements, and posture. Significant relationships between cocaine exposure and these outcomes remain in controlled analyses.