I am 23 weeks and just started growing a little more and my husband loves me in a 2 piece!! Even more than before I got pregnant, I say go for the 2 piece!
I've been wearing a tankini my entire pregnancy, 39weeks now. I was never completely comfortable with a 2 piece before pregnancy, but if you are then i say wear the 2 piece!
I'm 37 weeks and still wear a 2 piece swim suit. I started wearing spandex shorts instead of bikini bottoms though. It's more comfortable.
I personally would wear a two piece because I won't feel as constricted and plus it really matters what is more comfortable to u...honestly I would say go for the two piece. ...I don't know about it baby but when something is to tight she kicks like crazy lol