The deaths are among about 600 adverse reactions reported among women taking the contraceptives between 2007 and Feb. 28 of this year, Health Canada confirmed Tuesday.
Doctors and pharmacists who submitted the reports to the Canada Vigilance Program said Yaz and Yasmin are suspected in the 23 deaths. The reports say most of the women died suddenly after developing blood clots, a known risk with the pills.
Since 2007, Health Canada said the program has received reports of adverse reactions among 333 women taking Yasmin and 267 women prescribed Yaz.
Among those cases were 15 deaths linked to Yasmin and eight to Yaz. More than half of the women who died were under age 26, with the youngest being a 14-year-old girl. Most deaths reportedly occurred soon after the women starting taking the drugs.
Yaz and Yasmin are both made by Bayer and are often characterized as "newer-generation" birth-control pills. The contraceptives are produced using drospirenone, a synthetic progestin exclusively produced by Bayer.
In 2011, Health Canada issued a warning about the Bayer products, saying that although the risk of blood clots is rare, it is still 1.5 to three times higher with the drospirenone-containing pills than with some other birth control products.
An estimated one in 10,000 women on older-generation contraceptives will develop blood clots; with Yaz and Yasmin, that risk is estimated at three in 10,000.
While Yaz and Yasmin are suspected in the 23 deaths, Health Canada said reports of adverse reactions cannot be interpreted as showing cause and effect.
"Often it is not possible to determine if an adverse reaction (AR) reported to Health Canada is a result of using a specific health product," the department said by email. "Other factors contributing to the AR could be a person's health conditions or other health products they are using at the same time."
Bayer says the pills are safe and effective when used as directed.
There are a number of lawsuits either settled or pending against Bayer over the pills, both in the U.S. and Canada.
The first class-action suit against Bayer certified in Canada is being led by lawyer Matthew Baer. He and his law firm, Siskinds, are representing 13 families of women who they say died while taking Yaz or Yasmin, as well as hundreds of other Ontario women who say they suffered adverse reactions while on the pills.
Baer said his law firm has been contacted by more than 1,300 people inquiring about inclusion in the lawsuit.
The class-action suit alleges that the contraceptives increase the risk of serious side-effects, including blood clots. The suit further alleges that women died or were injured by Yaz and Yasmin.
One of the plaintiffs in the class-action is Stephanie Kerr of Tillsonburg, Ont., who said she took Yasmin for a month at about age 16 and developed blood clots in her lungs.
None of the allegations have been proven in court.
Kerr recalled she had been out running and suddenly was severely short of breath.
"I almost collapsed. I couldn't breathe. I couldn't take a full breath at all, and I kind of was starting to see spots. I knew I was going to go down pretty soon," she said. "I was really scared."
Kerr managed to get home and to the hospital, where doctors determined her blood was severely thickened and scans showed the bottoms of her lungs were full of clots.
She had to take blood-thinning drugs for six months, during which time she missed school. Her lungs were too weak to allow her to continue competitive dancing, which she was eventually forced to give up.
"It was painful for a long time. I couldn't walk very far without having to sit and take breaths," said Kerr, 20, who now teaches yoga.
Another lawsuit case is that of Miranda Scott, an 18-year-old University of B.C. Okanagan student who collapsed and died while working out in the gym three years ago.
Her mother, Chip McClaughry says she had been healthy all her life and it was a shock to the family when she died. She says she wants to see Health Canada and the manufacturer Bayer take the product off the shelf.
Bayer has already paid about $1.2 billion to settle, without admission of liability, thousands of lawsuits related to the products in the United States, but the company said Tuesday it stands by its products.
"Combined oral contraceptives, like Yaz and Yasmin, are among the most systematically studied and widely used medical products available today," the company said in a statement.
"Based on a thorough assessment of the available scientific data by regulatory authorities, outside independent experts and Bayer scientists, Yaz and Yasmin are safe, effective and have a favourable benefit-risk profile when used as directed in the Health Canada-approved product monograph."
The company also said: "It’s important to note that reported adverse events do not necessarily denote a direct causation with the product."
Certification of the Ontario lawsuit does not constitute a finding of fault against Bayer, but allows the case to go forward before the courts as a class action.
The company has filed a request for leave to appeal that certification, and that motion will be heard in an Ontario court on Sept. 4.
Meanwhile, Bayer said it is evaluating its legal options.
"No decision has been made on the merits of the case ... As a matter of policy, we will not comment further on next steps."
Baer of Siskinds said that after speaking to medical experts, he suspects the numbers of deaths and other adverse effects associated with Yaz and Yasmin are much higher than the figures reported to Health Canada.
"I would definitely think that there are way more than 23," he said of the reported fatalities. "Our firm has talked to the families of 13 people who have died and I certainly don't think that we've scratched the surface.
"I do think that there's significantly more than that out there that haven't been reported."