A male nurse has been arrested in Arizona for the sexual assault of a woman who gave birth while in a long-term vegetative state, police in the US state said on Wednesday.

The 29-year-old victim — who police said “was not in a position to give consent” — gave birth late last month to a baby boy, sparking an investigation.

The suspect's DNA was matched to that of the baby, leading to the arrest, according to police.

The 36-year-old suspect faces charges of one count of sexual assault and one count of vulnerable adult abuse, Phoenix police Sergeant Tommy Thompson told a news conference.

He is a “licenced practical nurse who was responsible for providing care to the victim during this time the sexual assault occurred”, Phoenix Police Chief Jeri Williams said.

The police chief said she had not encountered a similar case during 30 years in law enforcement.

The victim's family said in a statement carried by US media that she “has significant intellectual disabilities as a result of seizures very early in her childhood”.

The victim “does not speak but has some ability to move her limbs, head and neck” and “responds to sound and is able to make facial gestures,” the statement said.

“The baby, I am told, is doing good,” said Thompson.

“We can't always choose how we come into this life, but what we can choose to do as a community is love this child, and that's what we have the opportunity to do,” he said.

A lawyer for the woman's family has said the infant “has been born into a loving family and will be well cared for,” according to The New York Times.

The CEO of the nursing facility resigned following the scandal, according to a statement sent to media.

“This is a facility that you should be safe in and someone wasn't,” Phoenix Mayor Thelda Williams said.