The government study focused on an estimated 28,400 blood samples taken from a pool of 50,599 pregnant women in Alberta in 2005, The Globe and Mail said Wednesday. The samples were tested to determine the level of cotinine they contained.

Cotinine is considered a prime marker of exposure to cigarette smoke and non-smokers typically have less than 15 nanograms per milliliter of blood.

Those samples used in the study found between 5.1 and 55 nanograms, the report's authors said.

"The concentrations of cotinine measured here indicate that many pregnant Alberta women were smokers at the time of their blood sample collection, particularly in the youngest women examined, and in northern Alberta," the authors said.

Senior science adviser Stephan Gabos, who supervised the study, told the Globe and Mail the study's findings indicated pregnant women could benefit from learning more about the dangers of smoking.

"It shows we can never have enough in terms of education and intervention strategies and we still have some work to do in these areas," he said.