The child was pronounced dead at the John Hunter Hospital.
The male truck driver was taken to the same hospital for mandatory blood and urine testing.
One person is also dead after a bus and two cars collided at an intersection in western Sydney.
Emergency workers were called to the junction at Cabramatta West just before 5pm on Friday, police say.
The driver of one of the cars involved in the smash was pronounced dead at the scene.
No one else was harmed in the collision, including passengers who were on the bus.
The two surviving drivers were taken to hospital for mandatory testing.