Maternal Smoking during Pregnancy and Newborn Neurobehavior: Effects at 10 to 27 Days

Prenatal nicotine exposure via maternal smoking during pregnancy has been described as “the most widespread prenatal drug insult in the world”.1 Despite pervasive medical and societal sanctions against maternal smoking, between 11 and 30% of women continue to smoke during pregnancy.2–4 Rates are as high as 50% in high-risk samples, including young, poor, and urban populations.3, 4 Compared with other pregnant substance users, pregnant smokers are less likely to quit during pregnancy,5 and use cigarettes more frequently.3 Maternal smoking during pregnancy has been linked to low birthweight, admission to neonatal intensive care units, increased risk for sudden infant death syndrome,2, 3, 6 and long-term adverse neurobehavioral outcomes in offspring including attention deficits, hyperactivity, conduct disorder, and substance/nicotine use.7–10. Relatively less attention has been focused on neurobehavioral outcomes of maternal smoking during the newborn period. Documenting early effects of maternal smoking is critical for identifying vulnerability markers for intervention and prevention efforts, examining unfolding developmental pathways, and educating parents of exposed infants. Our group published the first study specifically designed to examine effects of maternal smoking on newborn neurobehavior controlling for likely confounds and involving biochemical verification of smoking.11 We utilized a neurobehavioral examination designed for examining effects of prenatal drug exposure in infants: the NICU Network Neurobehavioral Scale; NNNS.12 After adjustment for significant covariates, tobacco-exposed infants were more excitable, hypertonic, and required more handling compared with unexposed infants. Exposed infants also showed higher scores on the NNNS stress-scale—a scale demonstrated to reveal signs of neonatal abstinence following exposure to other drugs of abuse. Effects of maternal smoking/nicotine exposure on offspring neurobehavior and signs of abstinence in the immediate newborn period (up to postnatal day 5) have been corroborated by two additional studies. Both examined specific effects of maternal tobacco exposure and involved biochemical verification of exposure.13, 14 What remains unknown, however, is whether behavioral effects in the newborn period signify acute effects of nicotine, a withdrawal process, or more persistent dysregulation representing early vulnerability for later neurobehavioral deficits. This pilot study represents the first examination of specific effects of maternal smoking during on infant neurobehavior at 10–27 days. The half-life of nicotine is approximately 2.5 hours in adults15 and 9–11 hours in newborns,16--one of the shortest half-lives of drugs used during pregnancy17. Most nicotine withdrawal symptoms in adults peak at one week.18 Further, neonatal withdrawal from drugs with longer half-lives (e.g., caffeine) typically last less than 10 days17. Thus, examining infants at 10–27 days is less likely to indicate acute effects of nicotine or nicotine withdrawal and may represent a neurobehavioral profile more consistent with early vulnerability to long-term behavioral deficits. As in our prior study, 11 we utilized the NNNS to measure infant neurobehavior and cotinine as a bioassay for nicotine exposure. By design, smokers and non-smokers were matched for common confounders as in prior studies: socioeconomic status, alcohol use, and age. Exposed and unexposed infants were selected to be healthy, full-term, and normal birthweight.