Vaginal ultrasound during menstruation looks at the number of sinus follicles, which examines the basal state of the ovaries. If ovarian function is normal the number of sinus follicles is ≥9 bilaterally and <12 unilaterally. If the combined number of sinus follicles is less than 7, it is a sign of ovarian hypoplasia. If the number of sinus follicles is ≥12 unilaterally, it is considered polycystic ovary syndrome (PCOS) in conjunction with the patient's endocrine examination and the patient's symptoms of irregular menstruation and infertility, and ovulation induction is needed to get pregnant when suspected of having polycystic ovary syndrome. The endometrial lining of the uterus during menstruation is relatively thin, usually 2-3mm thick, if the endometrial lining of the uterus is thicker during menstruation, ultrasound should be rechecked after menstruation is cleaned up, and hysteroscopy is needed if endometrial polyps are suspected, and it is necessary to do ultrasound frequently during menstruation for infertile patients.