* France to stop reimbursing some contraceptive pills
* Bayer says will react once has detailed information (Adds Bayer comment)
PARIS, Jan 3 (Reuters) - 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, who 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 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 Sept. 30.
The moves comes weeks after Marion Larat, 25, sued Germany's Bayer and a French official over a stroke she suffered following use of the third-generation contraceptive pill Meliane.
An inquiry found her use of the pill could have been responsible for her stroke, which led to partial paralysis. Larat's lawyers argue Bayer should have withdrawn its pill from the market.
A spokeswoman for Bayer France said on Thursday: "We will assess any allegations once we have received detailed information and we will react appropriately."
In October, Bayer said it had set aside 200 million euros in the third quarter for litigation in the United States 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 gynaecologists, midwives and nurses are authorised 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. (Reporting By Chine Labbe, Thierry Leveque and Elena Berton; Writing by Nicholas Vinocur; Editing by Jon Boyle and Jason Webb)