During a natural miscarriage, abdominal pain occurs due to uterine contractions. This pain is caused by localized ischemia and hypoxia in the uterus and is a common occurrence. During a miscarriage, the uterus needs to continually contract to expel the gestational sac and decidual tissues. However, this pain is generally slightly less severe than the pain experienced during childbirth. After the gestational sac is expelled, the pain usually diminishes. Post-miscarriage, abdominal pain typically persists for two to three days. Once the residual tissues are expelled, the extent of uterine contractions gradually decreases, and the abdominal pain will also ease.