The U.S. Supreme Court backed the rights of pregnant workers, reviving a lawsuit by a former United Parcel Service Inc. driver who left her job when the company wouldn’t provide the less strenuous work recommended by her doctor.The justices, voting 6-3, sent the case back for a possible trial, which would center on UPS’s reasons for refusing to accommodate Peggy Young’s needs while giving temporary assignments to workers recovering from on-the-job injuries.