INDIANAPOLIS — A retired Indianapolis fertility doctor said he used his own sperm around 50 times instead of donated sperm that his patients were expecting, impregnating several women decades ago, but later denied it, according to court documents.

Dr. Donald Cline, 77, pleaded not guilty Monday to two felony obstruction of justice charges for misleading authorities who were investigating complaints from two of the now-adult children against him.

Cline is accused of being the biological father of at least eight people, the youngest of which would be about 30.

Cline, who now lives in the suburb of Zionsville, told six adults who believed they were his children that he had donated his own sperm about 50 times starting in the 1970s, a probable cause affidavit said. He had told his patients they were receiving sperm from medical or dental residents or medical students and that no single donor’s sperm was used more than three times.

One of the adult children took a saliva-based DNA test and found that she was related to at least eight other people in its database, the affidavit said. Meanwhile, two others also took DNA tests and learned their mothers both were patients of Cline and that they were related to 70 relatives of Cline, it said.