New research indicates premature infants whose mothers smoked during pregnancy had a higher heart rate and more trouble breathing than preemies whose mothers didn't smoke.

The study by researchers at the University of Calgary — the first to look at the effects of prenatal cigarette smoke exposure on infants' heart rate and breathing responses — is the cover story of the Sept. 1 issue of the American Journal of Respiratory and Critical Care Medicine.

The team looked at 22 pre-term infants born at between 28 and 32 weeks; 12 had mothers who smoked five or more cigarettes daily during their pregnancy while the mothers of the other 10 did not smoke.

Dr. Shabih Hasan, a pediatrics professor and co-author, said they found the preemies whose mothers smoked would pause their breathing and be slow to recover from it to breathe normally. They also exhibited higher heart rates than the premature babies whose mothers did not smoke.

Increased risk for sudden infant death syndrome

Hasan said smoking during pregnancy creates two significant risk factors for sudden infant death syndrome (SIDS).

"Not only does it raise the likelihood of a mother having a pre-term baby, who are already among the most vulnerable to SIDS, but it increases those infants' susceptibility to SIDS even further," he said Friday.

"We also know that the smoke-exposed babies or fetuses when they become children, they also have developmental and behavioural problems."

Sarah Spensley, one of the 10 non-smoking mothers who took part in the study, with her daughter Leah who was born eight weeks premature, said she hopes expectant mothers take the findings to heart.

"I think the more information that's out, the better and we can only hope that people take that information and use it to the best that they can."