A woman's breasts increase in size and fullness during pregnancy. Tender and painful breasts with a tingling sensation in the nipples is often one of the first signs of pregnancy. As the due date approaches, hormone changes will cause your breasts to get even bigger to prepare for breastfeeding. Your breasts may feel full, heavy, or tender.
In the third trimester, some pregnant women begin to leak colostrum from their breasts. Colostrum is the first milk that your breasts produce for the baby. It is a thick, yellowish fluid containing antibodies that protect newborns from infection.