You probably won't return to your pre-pregnancy weight for some time, but you will lose a significant amount of weight immediately after delivery. Subtracting one 7- to 8-pound baby, about a pound or so of placenta, and another few pounds of blood and amniotic fluid leaves most new moms about 12 pounds lighter.he weight keeps coming off, too. All the extra water your cells retained during pregnancy, along with fluid from the extra blood you had in your pregnant body, will be looking for a way out. So you'll produce more urine than usual in the days after birth – an astounding 3 quarts a day. You may perspire a lot, too.