Immediately after delivery and for the next several days, the uterus weighs about two pounds. You can feel it just below your navel as a firm mass about the size of a grapefruit. Large blood vessels bleed into the uterine cavity where the placenta was attached to the wall of the uterus. The uterus contracts firmly to prevent the uterus from filling with blood and clots and to prevent heavy blood loss. The following activities help the uterus contract