More than three million Canadians lost power during the 1998 ice storm. (CBC)

Babies born to women who were pregnant during the 1998 ice storm in Eastern Canada and faced unusual stresses show some developmental delays such as lower IQ scores, researchers have found.

The study, to be published in September's issue of the Journal of the American Academy of Child and Adolescent Psychiatry, used data from 178 women who were pregnant during the ice storm. The researchers also examined 89 children who were born then.

In January 1998, 30 people died and nearly 1,000 were injured when the storm dumped as much as 108 millimetres of freezing rain on parts of Ontario, Quebec and New Brunswick. More than three million Canadians lost power for as long as 40 days, according to the study.

The study is the first of its kind to examine the long-term health effects from the stress of natural disasters on mothers, the researchers said.

The children studied were about five years old when they were evaluated for their physical and cognitive behaviour.

Mothers who were highly stressed were more likely to see developmental delays in their children, the team found. The differences included IQ scores that were 10 points lower on average than for those born to less-stressed moms — a gap that could mean the difference between achieving an A or a B+ in school, the researchers said.

How mothers dealt with the emotional stress was not judged significant. "We expected that the greater the hardship, the greater the woman's distress, and that it would be that distress that would really be transmitted to the developing fetus," said the study's senior author, Suzanne King of the Douglas Mental Health University Institute in Montreal.

"But in fact it's not, it's just what happens to the woman. It's her objective exposure to the stressor."

The researchers looked at stressors such as the number of days a mother went without power or the amount of financial loss families faced.

Nathalie Frechette was about one week away from giving birth when the ice storm hit, and was one of the participants in the study.

Frechette had a wood-burning stove, so when the power went out, she and her extended family stayed at their home in Brossard, in southwestern Quebec.

"I had to think about how I would get to the hospital, if there would be electricity at the hospital or not, if my house would be full of persons when I come back," Frechette recalled.

Frechette said she's realized she can't feel guilty about an event that she had no control over.

Premature babies often experience developmental delays, but usually catch up midway through their school years. It's possible the developmental delays seen so far will also go away over time, King said. She continues to monitor the children in the study.

With files from the Canadian Press