OK, read the SA website as it explains all :)
Originally Posted by Helchops
No one single bag can be over 32kg for H&S reasons between Aus and UK. So you can have 2 bags each, say 20kg per bag for ease and be fine. Then 10kg for baby :) Or 25kg and 15kg for one of you, however it works, so long as its two bags, with neither one exceeding 32kg.
Pushchair. SA are good but expect for it to be checked into the hold somewhere along the line and to possibly not get it back till you land in Adelaide. You may, if it goes well get to keep it till the gate and then have it go in the hold and get it back in Singapore, but don't bank on it. Some people seem to, others don't. If its a bulky pushchair it will probably have to go in the hold as there may not be anywhere to store it in the cabin of the plane. So long as it folds down you should be good. Again, the SA website says about pushchairs so have a read and if in doubt, email them direct and get confirmation. I found this on the page I linked to
Infants are allowed 10kg of baggage. Additionally, a fully collapsible stroller or pushchair, carry-cot and infant food items may be checked in without charge.
It is not counted as part of your baggage that I know of. Nor does it state this. I think they balance the 10kg baggage with 10kg of pushchair so it evens out to 20kg.
FWIW I'd always say invest in a sling of baby carrier for airports and long haul travel. They are fab as give you hands free, no need to cart pushchair and you can also keep baby close and walk them up and down the plane without having to carry them in your arms. Soooooo much easier all round.