A nurse at a Phoenix nursing home who had been assigned to care for a woman in a vegetative state who was raped and later gave birth to a child was charged on Wednesday with sexual assault, the police said.

Detectives at the Phoenix Police Department took the nurse, Nathan Sutherland, 36, in for questioning in the case on Tuesday, the police said, and collected a DNA sample from him that matched that of the child, a boy who was born on Dec. 29. Mr. Sutherland was booked on Wednesday morning at the Maricopa County Jail on one charge of sexual assault and one charge of vulnerable adult abuse, the police said.

“Through a combination of good old-fashioned police work, combing through evidence, talking to people and following up on information, combined with the marvels of DNA technology, we were able to identify and develop probable cause to arrest a suspect,” Jeri L. Williams, the Police Department’s chief, said at a news conference on Wednesday.

Detectives started to focus on Mr. Sutherland because he was among the medical staff members at the nursing home, Hacienda HealthCare, who were assigned to care for the woman around the time last year that the police believe she was assaulted. The woman had been at the nursing home since 1992 and since then had been in the same condition, unable to communicate or move, according to medical records. A lawyer for the family on Wednesday said they were aware of the arrest but had no comment.