The OB/GYN department chief of a Connecticut hospital resigned a day after The Post reported he has been accused of having sex with his mistress in a sterile area of the hospital and taking explicit photos of himself there.

Dr. Stephen Carolan, 51, retains his privileges to treat patients at Greenwich Hospital, but remains the subject an internal inquiry.

“He stepped down on Tuesday,” said a hospital spokesman.

Meanwhile, The Post has learned that court papers from Carolan’s divorce from his second wife indicate he was arrested in Newport, RI, in August 2000 after he allegedly attacked her on their yacht. He pleaded no contest.