I had a 7 and a half lb baby. Placenta was probably 2 lb. probably lost 2 lbs of fluid. That gives me 9 extra lbs for some brown fat and an increased blood volume.  My baby is exclusively breastfed because I'm not a dumb fatass who pours formula down their kids throat because they're too lazy to nurse. Second baby. 5 years working in obstetrics. Pretty sure I've got this.