You may not think your baby is getting enough breast milk during the first few days of life when you're only making 1 to 2 ounces of colostrum a day, and that's an understandable concern. You do not have to — and shouldn't — wait until your breast milk come in to start breastfeeding your baby. The production of colostrum begins as early as the beginning of your second trimester of pregnancy. American Academy of Pediatrics. Colostrum is higher in protein and lower in fat and sugar when compared to transitional and mature breast milk, so it's easier to digest. Centers for Disease Control and Prevention. Verywell Family uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles.