Just draw a line on the stomach, that's all. If you wanted to.
I think it'd be hilarious, she could keep her phone and purse and other stuff in it and whip it out at funny moments. Plus child-birth isn't as painful because marsupial-babies are born no bigger than your finger and just crawl up into the marsupial's pouch on their own and continue growing from inside the pouch, it's incredibly cute.