A few days after your baby’s birth, your milk production increases or comes in. It is normal to feel some breast fullness, but engorgement, which can happen during the first week after birth, goes beyond normal fullness. When a mother is engorged, her breasts become full, firm, hard, hot, and sometimes painful.
Some think breast engorgement is caused by too much milk. But it is really caused by fluid build-up in the breast. If the milk is not drained often and well, extra blood, lymph, and other fluids build-up in the breast, too. Lots of IV fluids during labor can also be a factor.