It is more accurate to check the number of follicles in both ovaries on the second day of menstruation. After the onset of menstruation in women of childbearing age, the levels of estrogen, progesterone and inhibin A are at their lowest during the entire menstrual cycle, and the follicles in both ovaries have not yet developed and are of uniform size. Therefore, the number of ovarian follicles in both ovaries on the second day of menstruation accurately reflects the reserve function of women’s ovaries, and ultrasound checking of follicle number at this time is more accurate. Ovarian reserve function refers to the number and quality of follicles retained in the ovaries, and is an important indicator of a woman’s fertility. Checking the follicle count on the second day of menstruation is an important indicator of female fertility. To accurately assess the ovarian reserve function, in addition to follicle count, it is necessary to complete the examination of female sex hormones and anti-mullerian hormones. In order to determine the number of follicles, a woman needs to visit a regular hospital where a physician will formulate an examination and treatment plan based on the patient’s own condition. In the process of examination and treatment, it is necessary to follow the doctor’s instructions to avoid adverse consequences.