Re: Help us get through it
Can you email or speak to him by phone every day? Of course the safety of the baby has to be your first priority. You can also tell him when you write or speak on the phone about how sad you feel about what has happened--it will probably help him to hear that you are grieving about the accident too, even if you are far away.
Unless this is your 3rd or 4th baby and you have really fast deliveries, there should be some clues that you are getting close to time for the baby to come, and enough time for your husband to get back to you. If it would help you to feel more prepared, maybe ask a friend to plan to go to the hospital with you so if baby does come early you won't be alone.
Also, ask friends and family members to help you at home after the baby is born. That way your husband can come back for the baby's birth, but if his mother gets worse, he will be able to return to see her without leaving you stranded.