- If they are categorized as Maternity AND townified, it seems quite likely that the sim will "acquire" a custom Maternity outfit upon age up, like they do in all the other categories.
I tested that a while ago, and it didn't work. I didn't look deeper into it though.
Oh, and deleting through bodyshop is not a problem unless:
a) The outfit you are deleting is linked to a maxis texture, or otherwise connected to game files. This goes for things like unlocked career outfits, age conversions, and similar stuff.
b) This is the only outfit linked to its mesh. This will not cause any problems, but it leaves an unlinked mesh in your downloads, and that takes up space.
In fact, deleting outfits from within the game also deletes its thumbnail, which deleting it outside the game doesn't. So it keeps your thumbnail file from being full of crap you don't need.
Of course, if you're deleting a lot of stuff, you can just delete the thumbnail file.