Colostrum is the thick, sticky yellowish milk that baby will receive in his first few days of breastfeeding. You might see colostrum leaking from your breasts in the final weeks of pregnancy, or you may never see it at all — even when baby is beginning to nurse.
Your baby will only drink a tiny bit of this wonder-fluid at each nursing session, but that's all he needs. Colostrum is powerful stuff. It's packed with protein, antibodies, antioxidants, and vitamins — truly the perfect first food. Be sure to nurse frequently (about every hour or two with a four- to five-hour sleep stretch) in those first few days. This gives baby plenty of servings of colostrum while prepping your body to make a healthy supply of milk for the coming weeks and months.
Over the first week of baby's life, you should notice a shift from colostrum to thinner, whitish mature milk.