Nothing was ever established about how long Vala's pregnancy was. I assumed it was nine months, although only seven moths of real time went by between her departure at the beginning of season 9 and her return at the end of season 9. Still, even the primitive Ren Faire towns in the Ori galaxy must know how long a normal pregnancy lasts, and if Vala's were accelerated someone would and it would likely have caused more people to fear her and be suspicious. Or at the very least, everyone would have caught on that Tomin wasn't really the father. No, no one questioned anything, therefore she must have gone a full nine months.