A Baltimore County grand jury charged a Towson obstetrician yesterday with 125 counts of Medicaid fraud as well as obstruction of justice, theft and altering medical records, including an allegation that he billed for dozens of diaphragm fittings he hadn't performed.

Dr. Carter J. Williams, 42, practices at the Greater Baltimore Medical Center and has an office at the Physicians Pavilion there, said prosecutor Gale Rasin Caplan, director of the Medicaid fraud unit of the state attorney general's office.

Dr. Williams, of Wonderview Court in Timonium, has agreed to surrender Monday at the Golden Ring State Police barracks, Ms. Caplan said.

His attorney, Steven A. Allen, said yesterday that Dr. Williams had "always conducted himself properly and according to law. We are confident that when this case comes to trial, he will be found not guilty."

The grand jury charged Dr. Williams with falsely billing the medical assistance program for services to 124 patients.