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

Police said 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 suspect, who has been identified as 36-year-old Nathan Sutherland, faces charges of one count of sexual assault and one count of vulnerable adult abuse.

Sutherland is a "licensed 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".

A lawyer for the woman's family 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 the media.

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

The unidentified victim, who is a member of the San Carlos Apache Tribe, had been at the facility for roughly a decade.

Her caregivers have said they were not aware she was pregnant.

The care centre issued a statement saying that Sutherland was fired on news of his arrest.

"Every member of the Hacienda organization is troubled beyond words to think that a licensed practical nurse could be capable of seriously harming a patient," the statement said.

In a statement issued through their attorney, the victim's family sought to clarify her condition, saying that she was not in a coma but had "significant intellectual disabilities as a result of seizures very early in her childhood".