Switzerland's biggest health insurer CSS is supporting a young woman in her claim against Bayer, as the fall-out from alleged side effects of the German drugmaker's contraceptive pill Yasmin widens.

Bayer is already under fire in other markets over new-generation contraceptives. France will stop reimbursing prescription costs of some types from March, after a woman sued Bayer over alleged side effects.

CSS said on Wednesday it supported its client in her claim against Bayer and is acting as a joint plaintiff. The health insurer is demanding payment from Bayer to cover medical costs.

Swiss media reported the young woman suffered from a pulmonary embolism that left her severely disabled a few weeks after being prescribed the pill. The cost of medical treatment has amounted to some 600,000 Swiss francs ($648,600), according to reports.

A Bayer spokesman said the company could not comment on pending lawsuits but added the Yasmin group of pills had a positive risk-benefit profile based on extensive scientific data. He also said the decision which contraceptive to take rests with the patient and her doctor.

Bayer has so far agreed to pay a combined $750 million to settle 3,490 legal claims in the United States that Yasmin caused blood clots, and such injuries are alleged in a further 3,800 pending U.S. cases.

U.S. health regulators have added warnings to the labels on the pills to show they may raise the risk of blood clots.

Revenues from the Yasmin group of birth-control pills, Bayer's second-best selling pharmaceutical brand, are also in decline because of cheaper generic copies that are for sale in United States.