MONDAY, Oct. 4, 2004 (HealthDayNews) -- Smoking parents worn out by a colicky baby might want to try kicking the tobacco habit, a new study suggests.
"Mothers who smoke during pregnancy are twice as likely to have toddlers and infants who are colicky as women who do not smoke during pregnancy," concluded researcher Edmond Shenassa, an epidemiologist at Brown University Medical School.
Smoking by either parent around a newborn, as well as exposure to secondhand smoke by the mother outside the home, might also increase colic risks, he said.
According to Shenassa, anywhere from 5 percent to 28 percent of newborns are affected by colic, a discomforting gastrointestinal condition that usually appears between six to nine weeks of age.
The origins of colic remain unclear and, aside from attempting to soothe the baby, little can be done to treat its symptoms.
In their study, published in the October issue of Pediatrics, Shenassa and co-researcher Mary-Jean Brown reviewed findings from six major studies, comparing rates of colic in babies born to smoking or nonsmoking mothers.
There's already lots of evidence to suggest that "maternal smoking translates to environmental tobacco smoke for the baby," Shenassa pointed out. Environment, in this case, means both fetal exposure if the mother smokes during her pregnancy, or exposure through contaminated air or breast milk if she smokes after delivery.
Now, based on their review, the high rates of colic observed in babies born to smoking mothers suggest "a clear link between maternal smoking and colic," Shenassa said.
Although the researchers can't prove any specific mechanism of action linking environmental smoke and colic at this time, they say evidence is mounting that exposure to tobacco toxins increases infant levels of a gastrointestinal protein called motilin.
"Motilin promotes motility -- the movement of the gut muscle that pushes food through the gut from one end to the other," Shenassa explained. Too much motilin can upset the delicate newborn digestive tract, resulting in colicky symptoms.
And mothers-to-be aren't the only ones who need to quit smoking once they know a baby is on the way.
"Dads who smoke would also affect the environment," Shenassa said. In fact, anyone who smokes around a newborn or new mother could potentially have an effect on a baby's digestive health.
"For example, a mother could be exposed at work to secondhand smoke, then travel home," he said. Metabolites from that secondhand smoke can collect in a mother's breast milk and be transferred to her baby.
Experts estimate that about half of the 25 percent of American women who smoke continue to do so throughout their pregnancy, meaning that 12 percent of all babies born in the United States are exposed to tobacco toxins in utero.
For decades, experts at the American Lung Association (ALA) have been urging pregnant women not to smoke. Exposure to tobacco toxins during gestation or infancy has long been linked to increased rates of low birth weight, as well as asthma and other respiratory problems in young children.
Based on these latest findings, "we can now say that maternal smoking is related to a higher incidence of infantile colic," too, said ALA scientific consultant Dr. Norman H. Edelman.
The take-home message for new parents is easy, according to Shenassa: "Don't smoke. There are a lot of good reasons not to smoke. This is yet another one."
For more on the risks to children of environmental tobacco smoke, visit the American Lung Association.