Prenatal Smoking Exposure Linked To Irritability in Newborn Girls


BOSTON — Prenatal smoking exposure is associated with significant increases in irritability among newborn girls but not boys, according to a study presented at a meeting of the Society for Research in Child Development.

The fact that significant differences were not evident among male infants in the large, epidemiologic sample might suggest early links to later gender-specific differences in behavioral outcomes, said lead author Rachel L. Paster, a research assistant in the Centers for Behavioral and Preventive Medicine, Brown University, Providence, R.I.

All of the infants exposed to prenatal smoking exhibited increases in muscle tension, compared with unexposed infants, Ms. Paster reported in a poster presentation.

Using data from the New England Cohort of the National Collaborative Perinatal Project (NCPP), Ms. Paster and colleagues examined the effects of smoking during pregnancy on the neurobehavior of male and female newborns in a sample of 991 healthy mother-infant pairs recruited between 1959 and 1962.

As part of the NCPP, smoking was measured prospectively at each prenatal visit and newborn neurobehavior was assessed using the Graham-Rosenblith behavioral examination. For the current investigation, study participants were classified as nonsmokers, moderate smokers (between 1 and 19 cigarettes per day), and heavy smokers (20 or more cigarettes per day).

The investigators reduced the Graham-Rosenblith measure into three subscales—irritability, muscle tone, and response to respiratory occlusion—and then stratified the sample by sex. They used analysis of variance to examine group differences overall and by gender.

“We found significant differences between smoking groups for irritability in females, but not in males,” Ms. Paster reported. “[Least significant difference] tests revealed significant differences between the heavy smoking group and both the moderate and no smoking groups only for female infants, while significant effects of maternal smoking group on muscle tone emerged for both male and female infants.”

Least significant difference tests also showed different patterns of effects for males and females with respect to muscle tone. “For females, the heavy smoking group was significantly different from both the moderate and no smoking groups, while for males, the moderate smoking group differed significantly from the no smoking and heavy smoking groups,” Ms. Paster said.

Regarding the irritability findings, excessive irritability could indicate an infant withdrawal syndrome, Ms. Paster noted. Additionally, “irritability could potentially affect bonding and attachment with caregivers and may represent an early link to emotional dysregulation,” she said.

The hypertonicity findings “may be due to acute effects of nicotine and suggests problems with motor control,” Ms. Paster stated.

The findings of this study might be useful in identifying infants at risk for neurodevelopmental deficits and should provide additional incentives for abstaining from smoking during pregnancy, the investigators noted.

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