No experience here from me other than being a mother twice and having a daughter recently diagnosed BP. My advice would be to make sure that you take good care of yourself because if you do then Bubby will be taken care of as well.
Anyway.....it is a given that any stress will throw things off and I would imagine that you have been off of your meds and things from what you describe have been unstable. There is legitimate concern about what may happen after the baby is born until you are further stabilized.
I would make sure that you line up as much help as you can for the first few months that you are home with the baby. Is there anybody in your family that you can trust, who has been supportive of your BP that you can call on to do this??? In fact several people would be even better.
Your best chances of being stabilized after having the baby are your getting enough sleep (and we all know how difficult that is when you have a newborn

), eating right, getting good exercise, and avoiding as much stress as possible. OF course getting back on your meds and into therapy would be important as well.
Having somebody lined up to come in on a daily basis to help would be ideal....even having somebody live in even better. That way there will be somebody there to get up during the night with the baby in order to assist you. Of course, if hubby is able to do this then having somebody during the daytime will be all that is needed.
My advice would be to sleep/rest anytime bubby is sleeping. Having a baby without being BP takes a toll on women so it is imperative that you make whatever plans you can to have the help that you need so that you can avoid a postpartum depression.
It is a wonderful time having a new baby but also a very stressful time for a first time mother. And we all know what stress can do!!

So, lining up anything and everything you can to make sure that the stress levels are kept at bay and that you are able to get the proper rest that you need is vital during the postpartum months to follow.
Good luck....and keep getting the rest that you an bubby need ~ Goody