Anick Berard of the Universite de Montreal's Faculty of Pharmacy and the Sainte-Justine Hospital Research Center and graduate student Krystel Moussally conducted one of the largest studies ever undertaken by analyzing data from 3,354 Quebec women.

The first part of the research established that close to 10 percent of women between 1998 and 2003 used natural health products during their pregnancy. The most consumed natural health products by pregnant women: 19 percent use chamomile, 17 percent green tea, 12 percent peppered mint and 12 percent flaxseed oil. Berard and Moussally correlated these products to premature births and only one product had a very strong correlation -- flaxseed oil.

"In the general population, the average rate of premature births is 2 percent to 3 percent. But for women consuming flaxseed oil in their last two trimesters that number jumps up to 12 percent," Berard said in a statement. "It's an enormous risk."

The correlation existed only with flaxseed oil, yet women consuming the actual seed were unaffected, Berard added.

The findings are published at the Web site: umontreal.ca/english/index.htm.