"Upon arrival, the aircraft was met by a team of medical specialists and the relevant authorities, including the WA Police.
"We are unable to comment further on the infants' medical situation, however our thoughts are with the infant and family involved."
The plane was due to depart Perth again for flight D7237 at 6.50am but has been delayed.
"Looks like the doctor/paramedic and police officers have come out from the aircraft," wrote one traveller on Twitter while waiting for the next flight.
The airline has apologised for any inconvenience caused by the delay and said it would assist guests in re-booking.
Police will prepare a report for the coroner.