Police are investigating how a nine-month-old baby was critically injured at Lalor Park in Sydney's west.
Police and ambulance paramedics were called to the Koorool Avenue home just before 5pm on Wednesday following reports the boy had been injured.
He was taken to the Children's Hospital at Westmead in a critical condition with head injuries, police said in a statement.
Police from Quakers Hill are investigating.
A spokeswoman for the hospital said on Thursday night she could not say what the baby's condition was without parental consent.