I think that's really depend. I will be "sister" of my friend's wedding in September....and my friend asked her family and they are all ok about it...
But last time my friend just delivered in June, and I didn't go to hospital to visit. Well...that's really just because it's too far away and secondly, it's only 3 1/2 months still not that stable. If it's about 相沖, I think the pregnant mama should be 仲驚過佢.