You don't want them back if they can leave you when you are pg, honestly.
You can pretend it means something to them to let them to the birth, but really it will just make everything far more complicated.
I still get angry when I think of exp because he promised so much, in particular for DD - what he was going to teach her and where we would go to visit, how his brothers would love her and his mum. DD is coming up to 3 and he hasn't seen her since she was 6mo and won't even see her in a contact centre. Much as you can try to forget, every time your child asks about 'daddy' or does something that reminds you of them they come back to haunt you. I danced around him for nearly 2 years, letting him live with us after he left, letting him come to the birth, believing him when he said we would emigrate and I would become 'Mrs S*d' and even trying to continue with contact after he missed contact meetings and turned up hours late and drunk. It all culminated with him taking us to court so he could wriggle out of maintenance. It was not worth it at all. DD obviously doesn't remember him and he doesn't want the hassle of his child now. She simply doesn't exist for him any more.
We are going on holiday today and I've just had another call from CSA! Ex thinks they are stalking him on my behalf but honestly I just couldn't give a shit about him cheating DD out of money any more. However because it has now become a fraud issue they seem to be wanting me to join in for more evidence. I don't think I have the energy after 3 years and certainly didn't need a reminder before our holiday.
If our ex visits and actually gives 2 shits about your DC it may be easier to be forgiving or indifferent, as at least then you get some down time and your child has a relationship with at least one other person who loves them. Well, you'd hope so anyway!
Good luck OP.