Everything you asked up until --my wife is pregnant made sense.
At that point I think all you have written is just rubbish as there is NO WAY Australian Immigration is going to issue a student visa to a pregnant foreigner.
No one gets in to have babies there is NO visa for that. If you did NOT declare the pregnancy to Immigration in the application and you must NOT have or they wouldn't have granted any visa then when you rock up at the airport you will have a nice look out the window on the way back down the concourse to the first plane heading back to your country as you WILL both be be deported either that same day or the next. No way are you and she getting Customs and Immigration clearance if she is pregnant--it ain't happening mate. I can only assume you have omitted that detail on your application and think you can get away with it? Im telling you now, you don't have a prayer.
ADDED LATER--Normally I have learnt whatever Ozmaniac posts is pretty much correct. NOT this time and I challenge anyone to post positive proof Australian Immigration issues visas to pregnant overseas students when the birth of a child onshore in Australia allows that person more rights to citizenship. If this was correct, every pregnant 3RD world foreign student would be on a plane tomorrow. Even if it WAS possible--every 3rd world teen ager would be getting pregnant and applying knowing that once her child was born, she would end up with Australian citizenship. This is either the biggest back door loop hole to Australian citizenship or total bull sheet.
I say it is bull sheet. We just ain't that dumb as to let in pregnant girls, then have to be responsible for their hospital care and the child's right s to claim citizenship. Sorry Ozmaniac, on pretty much the majority of stuff you know the rules but on this one I will argue with you till Im blue.
Aussie is NOT going to bring in pregnant women who can then claim citizenship by having a child.
If that is the case , every 3rd world woman, pregnant , would be filling the planes on a daily basis.I have always had availability here for other Yappers to email me through Yahoo . Oz--pls do so with your proof. Normally I would bow to your advice but on this--no way. Dont for one minute tell me Australia has a ''back door'' to citizenship by coming here as a pregnant student. I dont believe it.