Police believe a baby boy was sitting on a driver’s lap when their car had a head-on crash in Sydney’s south-west last night.

Just before 6pm, a 31-year-old man and his 11-month-old son were driving along Clingan Avenue at Lurnea.

Their BMW sedan crashed head-on with a Mercedes, setting off the driver’s airbag.

Child remains critical following crash – Lurneahttps://t.co/mFaY6Rim2Z

— NSW Police Force (@nswpolice) February 25, 2019

A neighbour on the quiet residential street heard the crash and went outside, finding the man holding his infant son and crying for his wife.

Clingan Avenue at Lurnea

The baby boy suffered critical head and facial injuries and had to be airlifted to Westmead Children’s Hospital.

He remains there fighting for life.

Medical equipment left at the scene

Neither of the drivers were hurt, but have undergone mandatory testing.

Chief Inspector Bob Tunks has told Macquarie National News it looks as though the baby was sitting behind the wheel.

“It would appear to be the case that the child was unrestrained, sitting on the father’s lap.”

The crash investigation unit is continuing its inquiries.