2003-06-02
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.
This story has been adapted from a news release issued by
Brown University.
