Hysteroscopic surgery is usually done at the early stage of the follicle when the endometrium is thinnest, usually when the period is 3-7 days clean is better. Because the endometrium is very thin just after menstruation at this time, some lesions can be seen more clearly and will not be blocked by the endometrium. For example, if you look at endometrial polyps, fibroids and subendometrial fibroids, you will be able to judge the location and size of the polyps without the obstruction of the endometrium, and you will be able to see them more clearly. However, not every disease must be done 3-7 days after menstruation, for example, the review after hysterectomy depends on the recovery of the endometrium, you can choose the luteal phase to do hysteroscopy, which is the second half of the menstrual cycle. There are also some cases such as fetal residue and those who did not have a period after abortion, it is difficult to wait for menstruation and then do hysteroscopy, these patients can choose the appropriate period to do hysteroscopy. Therefore, it is up to the specific doctor to decide on the specific disease. For patients with residual fetus, some of them have residue in the ultrasound after abortion, and they have not had their period for two months, so they can have hysteroscopy at any time to find out where the residue is, and as long as it goes to the myometrium, they need further hysteroscopic electrodesis.