June 2, 2003 -- When a mother smokes during pregnancy -- even a few cigarettes a day -- her newborn is likely to be jittery, excitable, and difficult to console, signs of withdrawal similar to babies born to crack users.
That's the finding from a new study appearing in this month's issue of Pediatrics.
Much research looking at effects of smoking during pregnancy has focused on factors like low birth weight. Mothers who smoke during pregnancy are nearly twice as likely to have a low birth-weight baby. In fact, smoking is responsible for up to 30% of low birth-weight babies, writes lead researcher Karen L. Law, with Brown Medical School in Providence, Rhode Island.
First Look at Nicotine Effect on Baby Behavior
This is the first study to provide evidence of the effects of nicotine on the newborn's behavior, she writes. Cotinine, a chemical in nicotine used as a marker for nicotine levels, is readily passed from mother to infant -- with the fetus absorbing nearly as much as the mother does, she explains.
In their study, Law and colleagues identified 27 full-term babies born to mothers who smoked during pregnancy, and compared them with 29 babies born to nonsmokers.
Mothers were asked to estimate the number of cigarettes they smoked daily during pregnancy. Researchers also measured the amount of nicotine found in the mother's saliva after her baby was born.
These numbers were factored together through complex data analysis to produce a snapshot of the mothers' smoking patterns: Each smoked an average of seven cigarettes a day -- 13 cigarettes at the most, Law reports.
Researchers also analyzed the babies' behavior. Those in the "smoking group" were more excitable, more jittery, abnormally tense and rigid, requiring more handling to calm them, she says. They also showed greater stress to the nervous system, the digestive system, and their vision.
More Cigarettes, More Distress
The higher levels of cotinine, the more stressed the infants -- what researchers call a "dose-response" from smoking during pregnancy, she notes.
The nicotine-exposed infants were highly aroused and reactive, Law says. They showed signs of stress similar to withdrawal signs observed in infants born to mothers who did cocaine and other drugs, she writes.
Because infants were tested before they went home, researchers could rule out effects of second-hand smoke, she says.
Tobacco-exposed babies could flourish, with the proper child rearing, says co-author Barry Lester, PhD, in a news release. "If a behaviorally vulnerable baby receives attention and care, there is no reason to think that the child won't thrive. But we also know that the same baby is at risk for a poor development outcome if that child grows up in a stressed, low-income environment."
Smoking cessation programs are necessary to convince women to quit smoking during pregnancy, writes Law.