For what it's worth: A friend of mine's wife just gave birth, she has been athletic all her life, with usually two/three days a week spent in the weight room. She lifted heavy once a week. After the first trimester she switched to advance Yoga movements (which she was totally familar with...these can be demanding on anyone, even experience trainee's) with a lot of attention to posture/stretching and breathing patterns/control (she got her breathing and heartbeat down to 3 or 5 times a minute during home Yoga sessions). She even did neck bridges daily to help keep the spine in line and flexable, she told me. Everything went very well with the birth, short labor period witn no trouble at all. Doctor said it was a text book birth. She switched to becoming a vegetarian but did include dairy products in her diet. She got her fine figure back with-in a matter of three weeks after the birth, her husband happily said.
Of course all contact sports should be avoided , that's how she got pregnant in the first place. Good Luck.