A three-year-old boy has shot and wounded his father and pregnant mother with a handgun which he pulled out of the woman's handbag while searching for an iPad, US police say.

Both parents needed hospital treatment for non-life threatening injuries after the bullet went through his father's buttocks and into his mother's shoulder, Albuquerque Police Department officer Simon Drobik said.

The boy's mother, who is eight months pregnant, was kept at the hospital for observation.

The father has been released, said Mr Drobik, who was first to arrive at the scene of the incident at an Albuquerque motel on Saturday afternoon (local time).

"On the kid's side, it's a horrible accident that happened, but the parents are still culpable," Mr Drobik said.

"They should have secured the gun."

The couple could face felony negligence charges but the child will not face criminal charges, Mr Drobik said.

He said the woman told police she had purchased the 9mm gun the day before the incident.

The man is not legally allowed to have a firearm because he has previously been convicted of a felony crime.

The family, including a two-year-old girl and the children's grandmother, had been living in a motel for about a week with their two pit bull dogs when the incident occurred.

Following the shooting, the children were placed with child protection services for at least 48 hours.

The dogs were taken by animal control staff.

Reuters