There was no reason for Laura Lukasik to have difficulty walking one block from her car to work.

It was a warm March morning in 2006 and for the healthy librarian in her 40s, it was a quick and regular jaunt across York Boulevard to Hamilton Public Library's Central branch.

"My breathing was so laborious it was scary," she said.

After a trip to the emergency room, doctors said Lukasik had experienced a heart attack. They discovered large blood clots in her lungs.

"You're very lucky to be alive today," a doctor told her after she was admitted to the hospital's cardiac unit.

For two years, Lukasik's health was a test case while doctors tried to figure out what caused the clotting. She said she hadn't had any changes to her health other than taking Yasmin, a heavily-marketed birth control pill as prescribed to her by a specialist to help with her menstrual cycle.

Now, Lukasik is one of many women who are claimants in a class-action lawsuit hearing against Bayer Canada. They allege they developed life-threatening health complications after taking Yasmin or Yaz, produced by the pharmaceutical giant.

In March 2010, Lukasik's sister read an article about Ann Schwoob, a then-33-year-old mother from Vineland, Ont., who had clotting in her lungs after taking Yasmin, and launched a suit against Bayer.

"That's when it made sense," Lukasik said.

She then called Matthew Baer at Siskinds LLP in London, Ont., the lawyer handling Schwoob's case.

The lawsuit alleges that users of Yasmin, and its counterpart Yaz, are at a greater risk of developing clotting than users of other oral contraceptives and that Bayer didn't provide adequate warnings.

More than two million prescriptions filled in Canada in 2009

"This isn't a car accident," said Siskinds partner Mike Peerless. "This is Bayer, one of the largest companies in the world. They have many resources."

The difference between Yasmin and Yaz and other birth control pills is that it contains drospirenone, a new synthetic derivative of progesterone included in the drug to regulate the menstrual cycle.

Yasmin and Yaz were approved for use as oral contraceptives by Health Canada in 2004 and 2008 respectively. More than two million prescriptions for the contraceptives were filled in Canada in 2009, according to IMS Health Canada, a company that tracks prescribing.

Baer said there are 270,000 to 300,000 women in Ontario who could be eligible for financial compensation. About a thousand individual cases between Bayer and a plaintiff have already been settled in the U.S., averaging a  $218,000 pay-out, he said.

'There's no other explanation'

Marija Mandic, spokesperson for Bayer Canada, confirmed there are 13 proposed class-action lawsuits filed in Canada, plus one individual lawsuit. The hearing in Hamilton is the only active case.

"No class has been certified nor has any decision been made on the merits of the case," Mandic said.

That includes Lukasik's.

"There's no other explanation," Lukasik said, of the medical events she experienced.

Baer said if the case is certified, Siskinds will go forward with more plaintiff research to determine the medical causation between using Yasmin or Yaz and developing blood clots.

Despite the attention to this case, the drug is still on the market in the U.S. and Canada, a fact that is unnerving for Lukasik.

"More than anything else, [I want] that they do not sell this birth control anymore," she said.

The hearing will continue until Wednesday. Baer expects to hear if the judge will certify the class-action about four to eight weeks later.