French health regulators are studying limiting the use of contraceptive pills that carry health risks and will stop reimbursing prescription costs of some types from March, after a woman sued drugmaker Bayer over alleged side-effects.

An inquiry launched this week by the ANSM health regulator will review prescription practices by doctors, whom it says may be over-prescribing higher-risk third and fourth-generation pills.

While all oral contraceptives are associated with a risk of blood clots, a number of studies suggest the most recent brands, known as third and fourth-generation pills, carry a higher risk than their predecessors.

The European Medicines Agency says the risk of an embolism, or blood clot, is twice as high for women using third and fourth-generation pills than for those using earlier versions, although it remains low. The risk of a stroke is the same.

On Wednesday, France's health ministry said it would stop reimbursing prescription costs of third-generation pills from March 31, bringing forward a cut-off date from September 30.

The move comes weeks after Marion Larat, 18, sued Germany's Bayer and a French official over a stroke she suffered in 2006 following use of the third-generation contraceptive pill Meliane.

An inquiry found that her use of the pill could have been responsible for her stroke, which led to partial paralysis. Larat's lawyers argue that Bayer should have withdrawn its pill from the market.

Bayer declined to comment on the lawsuit on Thursday.

In October, Bayer said it had set aside 200 million euros in the third quarter for litigation in connection with its Yasmin/Yaz birth control pills, having already agreed to pay $750 million to settle 3,490 legal claims that Yasmin caused blood clots. Clots are alleged in a further 3,800 pending cases.

U.S. health regulators in April added warnings to the labels on newer birth-control pills sold there, saying they may raise the risk of blood clots.

France's health regulator said new-generation pills, which caught on because they reduced side effects from previous versions such as weight gain and acne, should only be prescribed by specialist doctors.

Currently gynecologists, midwives and nurses are authorized to prescribe them or renew prescriptions.

France, which reimburses 100 percent of prescription costs for regular birth-control pills, is under pressure to cut costs and reduce a 8.6- billion-euro deficit in its health system.