Germany drug company Bayer AG says it intends to buy California-based Conceptus to expand its birth control offerings. Bayer said Monday it would launch a public offer to pay $31.00 per share for all the stock in Conceptus, Inc. That means Bayer would pay $1.1 billion. Conceptus makes Essure, an irreversible birth control method in which metal and polyester coils are inserted to block a woman's fallopian tubes.