According to documents obtained from Health Canada, doctors and pharmacists say Yaz and Yasmin are suspected in the deaths of the women, who mostly died suddenly from blood clots.
One of the women, 18-year-old Miranda Scott, was working out on an elliptical machine at the Okanagan gym at the University of British Columbia when she collapsed and died three years ago, said her mother, Chip McClaughly, who is involved in a class-action lawsuit against Bayer, the maker of the birth-control pills.
"She fell backwards into the person behind her and then, I guess, when she was on the ground she said, 'I can't breathe,' and then, you know, she was gone," McClaughly said at her home in Delta, B.C.
McClaughly had no idea what had happened to her athletic, healthy young daughter, but she started to investigate.
"As soon as I heard that she had been on Yasmin, I thought, 'I'm just going to look that up,' and I did, and I thought: 'Oh my God, this is what's killed her," she said.
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Risk of blood clots rises
According to Scott's autopsy, she died of "disseminated intravascular coagulation," which means that blood clots formed inside blood vessels throughout her body.
Matthew Baer, of the Siskinds law firm, represents hundreds of Ontario women in a certified class-action lawsuit against Bayer that alleges Yaz and Yasmin have an increased risk of serious side-effects, including blood clots.
"[Scott's] autopsy report did say that there was a pulmonary embolism, which again is a blood clot in the lung," he said. "The major side-effect that we're alleging is worse with Yasmin than with the other oral contraceptives, [which] is an increase of blood clots."
Certification of the class action is not a finding of fault against Bayer.
While Bayer has already paid more than $1 billion to settle thousands of lawsuits in the U.S., the drug company tells CBC News it stands by its products.
Both Yaz and Yasmin, which are sometimes called "newer-generation" birth control pills, includes a synthetic progestin, drospirenone, which is exclusive to Bayer.
Teen girls as young as 14
In 2011, Health Canada issued a warning about Yaz and Yasmin, saying the risk of blood clots, which is rare overall, is 1.5 to 3 times higher with the drospirenone-containing pills than with some other birth control pills.
While one in 10,000 women on older birth control pills will develop blood clots, as many as three in 10,000 will develop blood clots on Yaz or Yasmin.
According to the documents obtained from Health Canada, between 2007 and February 2013, doctors and pharmacists have reported 600 adverse reactions and 23 deaths where Yaz or Yasmin were suspected. More than half of the reported deaths were women under 26, with the youngest age 14.
Most of the deaths reported occurred soon after starting the pills. In Scott's case, it was just over a month.
"And that was all it took, five weeks start to finish, and that was the end of a beautiful, beautiful girl," her mother said.
Lawyer says deaths underreported
Tony Merchant, a lawyer representing 1,000 women outside Ontario — including McClaughly — is seeking to certify a second class-action lawsuit in Canada against Bayer this fall.
Merchant said the number of deaths potentially associated with Yasmin or Yaz may be largely underreported because doctors may not realize there is a link between the cause of death and the risks of the pills.
"There are about 30 or 40 deaths that we think are known, but that is usually just the tip of the iceberg because all sorts of people will have died.... [Their families] don't know anything about the litigation, they don't know anything about the problem," he said.
Merchant said hundreds of patients who have approached his firm have had gallbladders removed, or have had strokes or blood clots and now must take blood thinners for the rest of their lives.
None of the allegations has been proven in court.
Bayer stands by Yasmin, Yaz
In a written statement to CBC News, Bayer said it is fighting the certification of the first Canadian class-action suit, the one in Ontario, which alleges women died or were injured by Yaz and Yasmin:
"We are very disappointed in Justice Crane's decision to certify a class in Ontario in an ongoing lawsuit regarding Yaz and Yasmin. No decision has been made on the merits of the case. We have filed a request with the Court for leave to appeal the decision and are evaluating our legal options... At Bayer patient safety comes first and we fully stand behind, Yaz and Yasmin."
Bayer is scheduled to appear in court in Ontario on Sept. 4.