Are you sure it is actually due to give birth, or is she just very swollen from ovulating now?. Quite often people think boas are actually gravid when in fact they are ovulating so they can later be be fertilized by the male. This is a very common mistake for people to remove the male far too prematurely before the egg follicles are able to actually be fertilized by the male. Boas typically just start "courting" the female around Fall/winter time and can last for months sometimes until they actually copulate. They typically have young anywhere from early August into October.
Usually by the time the female is gravid, the males will have lost all interest.
~Doug
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"a snake in the grass is a GOOD thing" 
