FRIDAY, Aug. 29 (HealthDay News) -- Babies born prematurely to women who smoked during their pregnancy may be at higher risk of sudden infant death syndrome (SIDS) than premature infants born to nonsmoking moms, new research suggests.

The Canadian study is the first to compare the breathing reflexes of "preemies" born to smokers versus nonsmokers. The researchers found that these tiny babies were more likely to have impaired recovery from pauses in breathing if their mother had smoked during her pregnancy.

"Our study shows that preterm infants make incomplete and/or delayed recovery from interruptions in breathing," study author and neonatologist Dr. Shabih Hasan, a professor of pediatrics at the University of Calgary, said in an American Thoracic Society news release. "This has clear implications for their risk of SIDS."

The study, published in the first issue for September of the American Journal of Respiratory and Critical Care Medicine, involved 22 infants born spontaneously between 28 and 32 weeks of gestation. Twelve of the babies had mothers who smoked five or more cigarettes daily, while the moms of the other 10 babies did not smoke during their pregnancy. The team assessed factors such as the infants' breathing rate, interruptions in breathing, breathing recovery time, oxygen saturation in the blood, and heart rate.

While the team found no differences between the two groups in terms of respiratory rates and the number of breathing pauses, infants born to smoking mothers showed increases in heart rate during a short period of lowered oxygen. Babies born to nonsmoking women did not show such a change, indicating that they were less stressed when oxygen levels dipped. Babies born to women who smoked during pregnancy also took longer to recover from depleted blood oxygen levels than infants born to nonsmoking mothers.

Besides the risk of SIDS, "inability or delayed recovery from repeated low oxygen episodes can also be detrimental to brain development," Hasan noted. "There is increasing evidence that infants exposed to prenatal cigarette smoke are at high risk for developmental and behavioral disorders."

Hasan said the findings may help doctors and parents better identify those premature babies at higher risk of SIDS, so that they can be more closely monitored at home.

More information

There's more on SIDS at the Nemours Foundation.