Monitoring the follicles will give an idea of the development of the follicles, the size of the ovaries, and will give an idea of the thickness of the lining of the uterus, which is very necessary for women with infertility. Based on the size of the follicles and the thickness of the lining, the doctor can instruct the patient on the timing of intercourse and what medications are needed. Follicle monitoring can also be useful for selective pregnancy, such as when a woman’s fallopian tubes are not working or are not open due to surgery or factors on one side of the tubes. Follicle monitoring can find out which side of the ovary ovulation, the fallopian tube is not good side in this month do not have intercourse, in the next month when the follicle is mature, the fallopian tube is open and then have intercourse, can improve the chances of conception, can reduce the occurrence of ectopic pregnancy. Therefore, in most cases of female infertility, doctors routinely require follicle monitoring, which can be performed on the 9th and 11th day of menstruation, ultrasound to monitor the development of follicles.