During the first week after delivery, as the colostrum is changing to mature milk, your breasts will become full. This normal postpartum fullness usually diminishes within 3-5 days. Engorgement may develop if your baby does not adequately remove the milk from your breasts. During this time, your breasts will feel hard, painful and hot.
To learn how to prevent and treat breast engorgement, download the following pdf file:
Breast Engorgement by Medela (165k pdf)