just found this
By the time you come to give birth, you'll be carrying quite a cargo! Just over a third of your extra weight will come from your baby, the placenta and the amniotic fluid. Here are some averages to give you an idea of how much they weigh:
* At birth, a baby weighs about 3.3kg (7.3lb).
* The placenta, which keeps your baby nourished, weighs 0.7kg (1.5lb).
* The amniotic fluid, which supports and cushions your baby, weighs 0.8kg (1.8lb).
But what about the other two thirds of extra weight? These can be accounted for by the changes that happen to your body while you're pregnant. Again, the figures are averages:
* The muscle layer of your uterus (womb) grows dramatically and weighs an extra 0.9kg (2lb).
* Your blood volume increases and weighs an extra 1.2kg (2.6lb).
* You have extra fluid in your body weighing about 1.2kg (2.6lb).
* Your breasts weigh an extra 0.4kg (0.9lb).
* You'll store fat, about 4kg (8.8lb), to give you energy for breastfeeding (Murray and Hassall 2009: 214).
By the end of pregnancy you may weigh about 12.5kg (27.6lb) more than you did before you became pregnant. Remember that this is only an average weight gain