If you were a healthy, lean weight prior to pregnancy, you should gain about 25 to 35 pounds during pregnancy. About half of that is baby, placenta, and amniotic fluid, which is lost at birth. The remainder (12 to 16 pounds for a lean woman and all the rest if you went into pregnancy overweight or gained more during pregnancy) of weight is in the mother’s tissues, including fluid (much of this is lost during the first few days after the baby is born, but the amount varies widely depending on how much fluid the mother retained in the last few weeks), blood, and muscle/fat stores. Most of the weight labeled as “mother’s stores” is fat weight, but some is muscle needed to carry around the excess weight. The fat is a calorie reserve for both pregnancy and breastfeeding.