The calorie stuff is true, I just want to point out you're growing more than just the baby during a pregnancy, though, which is why the weight gain recommendation for a healthy woman is 25-35lb, not just 8lb. Here's a breakdown quoted from The Bump. The fat deposits will be to prepare for nursing, and obviously there will be some variance from person to person on amounts.  1.5 pounds: the placenta 7 pounds: maternal stores of fat, protein, and other nutrients 7.5 pounds: your average full-term baby 2 pounds: breast tissue (we know it feels like so much more!) 4 pounds: increased fluid volume 4 pounds: increased blood volume 2 pounds: the uterus 2 pounds: amniotic fluid Total = 30 pounds