Baby boy critical with head injuries

A nine-month-old boy is in a critical condition in a Western Sydney hospital with serious head injuries.

The boy was taken to Westmead Childrens' Hospital on Wednesday afternoon after emergency services received reports he had been injured at a Lalor Park home.

His de facto father told staff at the hospital he'd dropped the boy at the home, which has since become a crime scene, the Seven Network reports.

The boy is not expected to survive, they added.

"Officers ... are continuing their investigations into the incident," a police spokeswoman said.

No one has been arrested over the incident.

No further detail was available.