Objective. This was a prospective study of the effects of maternal smoking during pregnancy on newborn neurobehavior, including dose-response relationships using self-report and a bioassay of nicotine exposure.
Methods. The sample included 27 nicotine exposed and 29 unexposed full-term newborn infants with no medical problems from comparable social class backgrounds. Mothers were excluded for using illegal drugs during pregnancy, using antidepressant medication, or if they consumed >3 alcoholic drinks per month. Nicotine exposure was determined by maternal self-report and cotinine in maternal saliva. The NICU Network Neurobehavioral Scale (NNNS) was administered by masked examiners in hospital to measure neurobehavioral function. NNNS scores were compared between nicotine-exposed and -unexposed groups including adjustment for covariates. Dose-response relationships with NNNS scores were computed for maternal salivary cotinine and maternal report of number of cigarettes per day during pregnancy.
Results. After adjustment for covariates, the tobacco-exposed infants were more excitable and hypertonic, required more handling and showed more stress/abstinence signs, specifically in the central nervous system (CNS), gastrointestinal, and visual areas. Dose-response relationships showed higher maternal salivary cotinine values related to more stress/abstinence signs (r = .530) including CNS (r = .532) and visual stress (r = .688) and higher excitability scores (r = .617). Cigarettes per day during pregnancy was related to more stress/abstinence signs (r = .582) including CNS (r = .561) and visual stress (r = .640).
Conclusions. These findings suggest neurotoxic effects of prenatal tobacco exposure on newborn neurobehavior. Dose-response relationships could indicate neonatal withdrawal from nicotine. Research directed at understanding the effects of cigarette smoking during pregnancy on infants can lead to improved public health outcome.