After ovulation, what is seen by ultrasound should not be called follicle, but corpus luteum, because the corpus luteum is formed after the rupture of the follicle and the discharge of the egg. It can be seen by ultrasound, and it will be known that there is a localized collapse, which indicates that ovulation has just occurred soon, and by ultrasound, it will be known that there is follicular fluid in the uterorectal fossa, which indicates that ovulation has already taken place. After ovulation, the corpus luteum will atrophy over time, if there is no pregnancy, the corpus luteum will atrophy after the basal body temperature will drop, when the basal body temperature drops about 24 hours after the menstruation, so after ovulation through the ultrasound to see is not the so-called follicle, strictly speaking, this is the corpus luteum, and sometimes the corpus luteum does not atrophy is known as the corpus luteum cysts, the diameter of which will not be more than 5cm, without special treatment. The diameter will not exceed 5cm, so there is no need for special treatment.