I found myself in territory, similar, but nowhere near as 'permanently away' as your DH might be. my DH works on weekends and is usually away the whole time...and of course DD decided to come on the day that he was over 300km away

I guess it is important to give both of you (and especially yourself) the peace of mind that it will be ok if he misses it. it didnt cross either of our minds and it really threw me when it happened and i found myself all alone with no idea of who to call for support. i guess my hint would be to have a support person in place that can be there to hold your hand tell you that it's going to be ok...although they cant replace your DH, at least you wont be alone and (importantly) your DH can feel comfortable leaving his gorgeous wife and baby in trusting hands IYKWIM.

HTH