If a woman’s menstrual cycle is usually 30 days or more, then ovulation will not occur on the 11th day of menstruation, as the follicles are still relatively small and have not yet reached maturity, but the menstrual cycle is different for each woman. Some women have a relatively short menstrual cycle, which may only last about 25 days, so ovulation may occur earlier, on the 11th day of menstruation, when the follicles may have already reached maturity and ovulation may occur. This situation varies with each person’s menstrual cycle and the ovulation period may also be different. You can observe the development of the follicles through ultrasound examination. Or you can monitor the ovulation test to make a clear diagnosis.