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.