Paramedics were called to a Stanhope Gardens house at 10:05am where they took over resuscitation efforts from the boy's parents.

A NSW Ambulance Service spokeswoman said the boy had suffered a cardiac arrest.

"It looks to be a traumatic cardiac arrest suffered as a result of injury," the spokeswoman said.

CareFlight's trauma team including a specialist doctor landed at the Blacktown Leisure Centre 300 metres away from the boy's home and were transported by police.

The team continued resuscitation as the boy was driven to the Children's Hospital at Westmead.