I've so been there. (More to my horror, now that I look back.) I suggest line up female friends or family that you feel totally safe with to be with you at the birth, as well as supporting you and the kids afterwards. Focus your energies on that. If you chase this bloke for contact, he'll just run and run.
This won't end up in the fantasy scenario you are hoping for (sorry, I know it's harsh at this stage, but..) There is no more vulnerable a position than labour and birthing, and if he were there it won't have the 'magic' effect you may be wishing for either. It'll just compound his sense of too much responsibility (and yes, of course, he's running away from exactly what he wished for and he should grow up. But let's think about your needs here.. )
His behaviour may be very unstable right now, so I suggest you create your own stability. He may come back as swiftly as he left, but he will probably leave again too. I suggest you get the locks changed, and take charge of your household. Do all the wonderful nesting stuff - get the food in, set up the nappy changing things upstairs and down, wash the babygros, pack your bag if you need one, etc, and have your friends on speed dial. You really can do it. I did, and though it was a pretty surreal time, the baby was just gorgeous.
(And, if you're wondering, the sire in question followed one of my friends to find out where I was, and barged round trying to come in on some weak excuse, etc. I wasn't there - still in hospital - so he was confronted with a friend who was getting the house ready. He played a lot of mind games round that time that really did my head in. I now realise I should have just focused on myself, and let the CSA do the rest. I did realise fairly quickly, though, and got on the right track. Life on my own was totally fine once I got the hang of it. It's much much lonelier in a bad relationship, I promise you.)
I look back now and I wonder if I had rocks in my head to stay with such a strange person for so long. However, onwards and upwards.