Washington, Dec 2 : It has been shown that babies exposed to tobacco in utero are more likely to have a low birth weight and are at increased risk for sudden infant death syndrome. Now, a new study has revealed that these infants are also less likely to self-soothe and are more aroused and excitable than newborns whose mothers did not smoke during pregnancy.
The new study has been conducted by researchers at The Miriam Hospital's Centers for Behavioral and Preventive Medicine. "A baby who is harder to soothe and more irritable could be more difficult to take care of and could potentially affect the developing mother-child relationship, especially for mothers who are already stressed and have fewer resources," says lead author Laura Stroud, PhD, a psychologist with The Miriam Hospital's Centers for Behavioral and Preventive Medicine.
In the study, Stroud and colleagues from Women and Infants Hospital in Providence, RI, and the Warren Alpert Medical School of Brown University focused on newborns between 10 and 27 days old.
All 56 babies - 28 smoking-exposed and 28 unexposed - were healthy and full-term. Maternal social class, age and alcohol use were similar in each group.
Mothers in the study were assigned to the smoking or non-smoking group based on self-reports of cigarette use during pregnancy assessed shortly after babies were born.
This was verified biochemically by measuring cotinine, the primary metabolite of nicotine, in the mother's saliva. Cotinine is readily passed from mother to infant, with the baby absorbing nearly as much as the mother does.
On average, the number of cigarettes mothers smoked each day decreased over the course of the pregnancy, from about 15 cigarettes per day in the first trimester to approximately five cigarettes in the third trimester.
Postnatal smoke exposure was quantified by infant saliva cotinine levels. All infants were then assessed using the Neonatal Intensive Care Unit (NICU) Network Neurobehavioral Scale, a tool developed for the National Institutes of Health to measure the effects of prenatal drug exposure in infants, including withdrawal and general signs of stress.
The researchers found that smoking-exposed infants showed a greater need for handling, or external intervention, in order to be soothed and calmed down. These babies also tended to be more easily aroused and excitable.
The study is published online by the Journal of Paediatrics.