The surprise takeover bid for A. H. Robins Co. by the French pharmaceutical group Sanofi may prompt other offers for Richmond, Va.-based Robins, but no U.S. company is likely to enter the fray, industry analysts say. Sanofi's bid, announced Thursday, came during talks between Robins and Rorer Group of Fort Washington, Pa., to revise their $2.6-billion merger agreement. "The (U.S.) drug industry is very gentlemanly. They may not want to come in because Rorer has put its cards on the table," said analyst Rita Freedman of Provident National Bank. Robins spokesman Roscoe Puckett said Sanofi's offer would provide the $2.5 billion in compensation required to cover legal claims associated with Robins' Dalkon Shield birth control device.