On the fourth day after a medical abortion, if there is pain in the stomach and also back pain, it is mainly considered to be due to uterine contractions. When the gestational sac is expelled, the uterus has to return to its pre-pregnancy state through constant contractions, which can lead to abdominal pain, which is similar to menstrual cramps. The presence of back pain is also related to pelvic congestion and decreased hormone levels. If the pain is only mild, no special treatment is usually needed. However, if the pain in the stomach is particularly severe, it is necessary to consider whether there is incomplete abortion or infection. In this case, it is necessary to review the ultrasound to understand the recovery of the uterus, and if necessary, it is necessary to perform an emergency operation to remove the uterus.