Ok, I stand corrected with the qantas allowance and assumed it was the same as other airlines. It does say they will carry a collapsible pram and car seat for children under 12.

All airlines are required to carry carseats due to the new car seat laws. However I know Virgin Australia does not carry a pram for a child (infant yes, but not a paying child), free of charge. It has to be part of your paid baggage allowance..

However, it is something I suggest people check with each airline. It is within the small print and can vary from each one.