If you don't have advanced notice or prefer not to use hormones or medications, you can still make milk for your baby! (lactationlink.com)
Your milk duct system becomes fully developed sometime during your second trimester, so you can make milk for your baby even if he arrives prematurely. (babycenter.com)
Learn how your breasts prepare for breastfeeding during pregnancy, and how you'll make milk for your baby after he or she is born. (babycenter.com)