congratulations to you first.
my first tip is:

1. PATIENCE.With all the hormonal changes your wife will go through your patience will really be tried.
   2.After the baby is born,buy your wife the best lingerie you can afford cos dressing up after delivery is pretty hard.bras dont fit,pants dont fit blouses noting fits.Actually that the best gift you can give your wife.
   3.Constantly remind your wife that shes beautiful and not fat.Go with her to the gym.
   Just enjoy each step of the way its pretty fun and youll learn a lot.
   Congratulatios to the both of you again.