Our bub hated being naked when he was little - so t-shirts and pants were much better for us than any sort of suit. We could change whichever half he had grotted on and he wouldn't be sad. Some hospitals are quite cold, so take a jacket or cardigan as well in case they have hyperactive air-conditioning.

If you can find pants-with-feet they were much better than socks, which would not stay on.

And if you or your DH have big hands then consider wider rather than narrower sleeves. There was no way my DH could get a wondersuit on DS! Target make pyjamas which have wide sleeves and snaps on one shoulder - they were the easiest things to get on.