There is no uniform standard for follicular development on the 16th day of menstruation, each patient has a different menstrual cycle, different ovulation time, the speed of follicular development is not the same, the individual variability is very large. Due to the influence of emotions or the impact of exercise, weight loss, or work and study stress and other factors. The size of the follicle development standard is also different in different months, according to the specific circumstances to determine whether the follicle development is standard or not. Follicle monitoring is a continuous process, if the menstrual cycle is 30 days, it is recommended to monitor the follicles from the 9th day of menstruation, with dominant follicles, the follicle growth rate of about 2mm per day, it is considered normal. The normal development of follicles on the 16th day of menstruation should be determined in conjunction with the entire testing process.