Thing is, a lot of marriages founder when the first baby arrives due to the selfishness of the man. Because a lot of women don't really notice how much the Relationship (prior to having DC) revolves around the meeting of the man's needs. (I know, I know, not YOUR nigel, plenty of relationships are mutually beneficial and luvverly and all that). Women in relationships with selfish men, with men who can't fully comprehend that women are people but see them as there to make the man's life happy, have often got accustomed to letting him get his own way, letting him choose what film to see, where to go on holiday, what to watch on the telly, what to have for dinner, because, oh well, you know, it's only a little thing, no point having a row about it, I don't really mind. Etc.
And then there's a baby. Actually, sometimes it starts during pregnancy. DV, that is. The woman is being sick all the time, she's tired, she doesn't want to go out clubbing till 4 am any more and she's not in the mood for sex right now either. Nice men accept this even if they are a bit disappointed. Abusive men start to piss and moan about how she's 'changed'.
When the baby's actually arrived and the woman is, understandably, absorbed in taking care of it, and recovering from the birth, selfish men act up. Some go out and get pissed, some start affairs because the poor diddums feels neglected... Some actually get violent.
The main point is, OP, if your H is an arse, he isn't going to improve and the sooner you get rid, the better. Sorry love, but that really is the bottom line.