What is the earliest that breast milk will come in during pregnancy?

Actually, women don't lactate during pregnancy. That doesn't occur until after delivery, usually a few days or so. The production of colostrum -- a "premilk" -- occurs around week 20 of pregnancy and continues for a few days after delivery until real milk is produced. Wrong. Colostrum CAN be the first sign of pregnancy. ------ Though breast tenderness and swelling are usually the most obvious signs.