I see something that is very common in a marraige and kudos to you for recognizing it and wanting to do something about it. She is very lucky to have you. The stress and fear of an impending child is enourmous for both people as their independance and freedom is threatened. Your other friend signifies freedom and your wife is so incredibly vulnerable, she couldn't even run to save her own life. If I was in your shoes, I would say 'honey, this is going to be big and I'm concerned that we will lose the intimacy between each other" and go from there. As this thing begins to solve itself, your desire for the other woman will wane. All my best to you and your little family