On top of that, he is seeking and receiving attention outside the marriage.
SW and kids were gone for several weeks and when the cat was away, he could play.
Even as energized as SW was, perhaps she came home exhausted or moody - maybe the homecoming was a drag instead of a celebration. Then, as soon as they return home, SW leaves for a conference, and CW is in charge of the kids on his own. That can be a jolting transition to go from a carefree time with no family to having both kids all day (who might also be tired and out of sorts after traveling and switching scenery, etc.)
I
I think he wanted out from the financial responsibilities of the growing family. The pregnancy might have been "welcomed" but also a reminder of money issues, and being tied down....when he had side action that reminded him he still had game.
I do think the pregnancy was part of his decision and he knew full well he was killing yet another life when he killed his wife.
In my observation, opinion only, men usually don't leave their wives unless there in another woman to go to. But, husbands will kill wives over money. (Yes, you can point out exceptions, I know.)
jmopinion