A new study suggests that even casual smoking during pregnancy harms a fetus, producing behavioral changes similar to those in babies born to mothers who use illegal drugs.
Women who smoke just 6 to 7 cigarettes per day give birth to babies who more jittery, more excitable, stiffer and more difficult to console than newborns of nonsmokers, report Brown Medical School researchers in the June issue of the journal Pediatrics. The higher the dose of nicotine measured in a mother, the greater the signs of stress in her new baby.
This is the first research paper to show that nicotine exposure in the womb produces behavioral changes in babies similar to those found in newborns of women who use crack cocaine or heroin while pregnant. The data suggest “neonatal withdrawal” from nicotine, said the authors.
“We have a legal drug in nicotine that may have the same toxic effect as illegal drugs,” said Karen L. Law, who led the study. Law suggests that public health officials consider stop-smoking interventions that would produce healthy newborns for women who currently smoke.
“These findings require us to take a step back,” she said. “What are Surgeon General warnings doing to stop smoking, given that the percentage of smokers is similar in the pregnant and general populations (about 18 percent and 25 percent respectively)? It is a huge public health concern that so many people are suffering the costs of smoking, including newborns.”
Brown researchers are conducting a follow-up study of tobacco-exposed infants in their first month of life to better understand the lingering effects from nicotine.
Previous research has linked as few as 10 cigarettes daily during pregnancy to low birth weight babies. The Brown study lowers the threshold for causing fetal impairment to 6 to 7 cigarettes a day. This new study opens the door to further research, said Law. “We don’t know if a woman quits smoking six months into pregnancy will that make a difference? Given that we have found a behavioral outcome in newborns at a lower dose of six cigarettes a day, would we find an effect at three cigarettes as well?”
The study involved 27 tobacco-exposed and 29 unexposed full-term newborn infants from comparable social backgrounds with no medical problems. The “nicotine” infants were more excitable, abnormally tense and rigid, required more handling and showed greater stress, specifically in their central nervous, gastrointestinal and visual systems.
To some extent, “this is science shaped by culture,” said Barry Lester, senior author of the study and an expert on maternal drug exposure. “We tolerate smoking in ways that we don’t tolerate drugs. Eighteen percent of women smoke in pregnancy. About 3 to 5 percent of pregnant women use cocaine. Yet everyone is worried about cocaine.”
If cigarettes cause a fetus the same injury as illegal drugs, “do we yank newborn babies from women who smoked during pregnancy?” Lester said. “Here, a legal drug is showing the same effects as an illegal substance for which protective services will remove babies from their mothers. We have not faced this policy question about a legal drug before, because this scientific information was not available. We need to re-look at how we evaluate a fit mother.”
Tobacco-exposed babies could flourish, with the proper child rearing, said Lester. “You have to apply the findings in context,” he said. “Yes, this is correctable. 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 developmental outcome if that child grows up in a stressed, low-income environment, where effects of exposure get exaggerated.”
To conduct the study, Law collected self-reports of smoking from new mothers. She correlated the information with a biological marker of nicotine, called cotinine, collected from saliva of the mothers. This is the first study of its kind to include cotinine. Law also conducted a behavioral exam for newborns within 48 hours of birth, designed to measure drug effects. Women were excluded from the study for use of illegal drugs, antidepressants and alcohol. All babies were full-term, and the researchers controlled for low birth-weight and other factors.
Law conducted the study as a senior at Brown, where she is now a third-year medical student. She led a six-member team of specialists in infant development, addiction behavior and smoking cessation. The study was supported in part by a Brown Medical School Summer Research Fellowship and by grants from the National Cancer Institute and the Department of Psychiatry and Human Behavior at the Brown Medical School.
Materials provided by Brown University. Note: Content may be edited for style and length.
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