Endometrial detachment may cause severe pain in the lower abdomen, mainly due to the following reasons: 1, incomplete endometrial detachment: incomplete detachment causes uterine contraction, resulting in pain in the lower abdomen; 2, endometrial inflammation: for example, when endometrial detachment occurs during menstruation, it leads to pain in the lower abdomen due to the influence of inflammation; 3, the patient’s own underlying co-morbidities: uterine fibroids, endometrial polyps, endometriosis in adenomyosis, and so on, can also lead to severe pain in the lower abdomen during the detachment of the endometrial lining.