Cramps in the lower abdomen after menstruation are signs of what?

Normal. During your menstrual period, your uterus contracts to help expel its lining. Hormone-like substances (prostaglandins) involved in pain and inflammation trigger the uterine muscle contractions. Higher levels of prostaglandins are associated with more-severe menstrual cramps. This may continue even after bleeding has stopped. If severe, see MD about endometriosis.