Sorry, wrote a long post, and lost it.
OK. I'm not a counsellor, and I don't know you, so I'm going to throw things.
One possibility is that having children, even with a straightforward birth, throws relationships into relief, and hidden stresses come to the fore; could it be that that's what this touches on?
Another possibility is that it has touched on your deepest wishes and desires in an intimate relationship, and your fears. Possibly the need to believe your partner can be utterly relied on if you ever find yourself utterly vulnerable or incapable of preserving yourself/those you love, indeed, relied on to "rescue" and "save" you?
I suppose I'm thinking about how you've written your post. You asked "why" you can't forgive him, as though you really feel the need to, but can't.
I guess, the logical answer would be to recognise that he was vulnerable, too, and was not gifted with a special power to make it safe, and to forgive him from that position.
As you know, attending ante-natal classes wouldn't have made the difference.
but it's also possible that the whole episode has made you question how your partner operates in the world, how he interacts with you, his overall level of care and concern, and so on.
for all I know, the reason you can't forgive him is because he was a bit rubbish - I don't know.
May I ask you something - what are the power-relationships like in your partnership? Do you cede him a lot of control, in return for a (hope-for) care and protection, and delivering the goods at the end of the day?