Maternal smoking during pregnancy and neonatal behavior: a large-scale community study.

OBJECTIVE To investigate the influence of prospectively measured smoking during pregnancy on aspects of neonatal behavior in a large community sample. METHODS Participants were mothers and infants from the Providence, Rhode Island, cohort of the National Collaborative Perinatal Project enrolled between 1960 and 1966. Mothers with pregnancy/medical complications and infants with medical complications and/or born premature or of low birth weight were excluded. The final sample included 962 mother-infant pairs, 23% of whom were black. Maternal smoking was measured prospectively at each prenatal visit. Neonatal behavior was assessed by using the Graham-Rosenblith Behavioral Examination of the Neonate. Items from the examination were reduced to 3 subscales: irritability, muscle tone, and response to respiratory challenge. RESULTS Sixty-two percent of the sample reported smoking during pregnancy, with 24% of smokers reporting smoking 1 pack per day or more. We found a significant influence of maternal smoking exposure (none, moderate/less than 1 pack per day, heavy/1 pack per day or more) on irritability and muscle tone in the neonate, with exposed infants showing greater irritability and hypertonicity. Effects remained significant after controlling for significant covariates: maternal socioeconomic status, age, and race and infant birth weight and age. Posthoc tests suggested particular effects of heavy smoking on increased infant irritability and both moderate and heavy smoking exposure on increased muscle tone. CONCLUSIONS In a large community sample, exposure to maternal smoking was associated with increased irritability and hypertonicity in neonates. Exposure to maternal smoking did not influence neonatal response to respiratory challenge. This study is the largest-scale investigation to date of the effects of maternal smoking (heavy and moderate) on examiner-assessed neonatal behavior. Given the associations between both maternal smoking and infant irritability and later behavioral dysregulation, results have important implications for early identification and intervention with at-risk offspring.