Haha...great question!
Not a thong girl, personally. Strings are now cutting off my circulation on my hips and they hurt...sorry, DH!

I'm still wearing my same-sized bikini hipsters or bikini low-cuts well under my (low) belly...I also sometimes wear my size-up, old bikinis and they feel like granny panties to me, but they're a heck of a lot more comfy. I'm sticking with pretty much all cotton at this point, too. I never have worn maternity undies with any of my pgs, but came close with Kiley and Ellie...hopefully I won't be that big at the end this time since I started out smaller. I don't think I could do high-cut or boy shorts...that would drive my crazy on my belly.