A lot of trouble: a lot of trouble is to use some instruments and equipment to do inspection and testing. At present, the commonly used method is to observe the size of follicular growth by ultrasound. Generally speaking, when the follicle forms about 2 cm, it may be close to ovulation day. After a series of measurements, we can know when the follicle will disappear in the ovary, so we can determine the ovulation date on the same day. By using this method, we can accurately judge the date of ovulation and calculate the time of menstrual cramps.
Furthermore, you can also buy small reagents in western pharmacies to detect ovulation days. If the concentration of luteinizing hormone is quite strong, it means that ovulation will occur after 24 hours, so it can also be inferred when menstruation will come.