The reason for not having menstrual cramps after having children may be due to the following reasons: 1. Before having children, menstrual cramps occur before pregnancy because the endocervix is relatively narrow and tight, causing relatively difficult menstrual blood flow, the uterus will contract so that the menstrual blood in the uterine cavity is discharged, there will be pain in the lower abdomen, after having children the state of the endocervix being too tight will be improved and the symptoms of menstrual cramps will disappear. 2. For example, due to the abnormal position of the uterus, menstrual blood cannot be discharged from the uterus as soon as possible because of the forward-flexed position or the backward-flexed position of the uterus, and if menstrual blood has to be discharged, the uterus will contract, which will cause menstrual pain.