Your own weight must have gone down as baby would weigh around 4lbs let alone placenta, water, boobs, extra blood etc. Your body has probably just been giving everything to baby so when you give birth you will weigh about a stone less than you did to start with, unless your under weight then def speak to you midwife, you don't want your body to suffer too much. If your planning to breast feed you might need a bit of fat stores to help with that too, thats normally another few pounds that women gain as well in preparation. I lost over a stone in tri 1 from all the nausea but I'm thinking of that as my starting weight now otherwise I've only put 3lbs from pre-pregnancy weight which I know is wrong as baby wieghs more than that by now! Plus I don't stop eatting now so def put some fat back on!