Women trying nicotine replacement therapy to quit smoking while pregnant might find that they end up with a fussy baby, according to an observational study.
Women who used nicotine replacement therapy -- patches, gum, or inhaler -- saw an adjusted odds ratio of infantile colic of 1.6 (95% CI 1-2.5, P=0.03), reported Ioanna Milidou, MD, of Aarhus University Hospital in Aarhus, Denmark, and colleagues in the March issue of Pediatrics.
By comparison, smokers' babies were at 30% higher risk of colic than those not exposed to any source of nicotine in the population-based birth cohort study.
Nicotine replacement therapy has been considered a safer alternative to continued smoking in pregnancy and thus seen increasing use among pregnant women, Milidou's group explained.
These results shouldn't be considered a contraindication for nicotine replacement therapy for women who can't stop smoking without it, they cautioned.
But the risk seen does warrant more investigation into safety for use in pregnancy, they added.
Infantile colic generally resolves on its own eventually, but until it does the paroxysms of hours of crying and fussing every day for weeks on end "pose a burden on the affected families and may even trigger violent behavior toward the child," Milidou and colleagues noted.
Since smoking is a known risk factor, the researchers examined the role of nicotine among 63,128 mother-child pairs in the prospective Danish National Birth Cohort.
Interviews with the mothers during pregnancy and six months after delivery indicated that 23.8% smoked while pregnant.
A further 0.3% (207) had used nicotine replacement therapy without resorting to cigarettes and 2% (1,245) had both used it and smoked while pregnant.
The overall rate of colic, defined as three or more hours of crying and fussing a day for at least three days a week unrelated to teething or known illness, was 8%.
But that proportion went up to 9% for smokers and to 11% for nicotine replacement therapy users.
After full adjustment for parental sociodemographics, coffee consumption, maternal age, and binge drinking, the odds of colic were the same whether infants had been exposed to nicotine replacement therapy alone or with prolonged smoking during gestation, at a statistically significant 1.6 versus no exposure.
Together with the similar magnitude of risk after exposure to smoking alone, "this finding indicates that nicotine may be the component in tobacco smoke responsible for the increased risk for infantile colic," the researchers concluded.
Some suggest that the link between smoking and colic is almost entirely due to uncontrolled confounding, they noted but pointed to the similar results in their adjusted and unadjusted analyses.
Exposure to smoke from the father or partner didn't have any impact on the likelihood after adjustment for the mother's smoking status.
The researchers cautioned that their observational study couldn't rule out unmeasured or residual confounding, and that the number of women who used nicotine replacement exclusively was small.
A causal role for nicotine is plausible, they suggested, because it interferes with serotonin in the developing brain and intestinal system, along with gastrointestinal vasoconstriction that would increase bowel motility.
