A normal couple with a normal sex life has a 90% success rate of pregnancy within one year. A normal menstrual cycle lasts 28 days and includes the menstrual phase, the follicular phase and the luteal phase. During the late luteal phase of the previous menstrual cycle, a group of follicles have started to grow until the follicular phase. On day 7 of the menstrual cycle, only one follicle in this batch can eventually continue to grow because of the hormonal effects in the body, the rest of the follicles will be atretic until day 11-13 of the menstrual cycle when this follicle can grow up to 18mm, i.e. to the pre-ovulatory state. At this time, a hormone called luteinizing hormone will reach its peak, which signals the rupture of the follicle and the expulsion of the egg. During the natural cycle of ovulation monitoring, the urine LH test is used to determine if ovulation is imminent. If the test paper is positive, the patient is instructed to have intercourse, after which the egg and sperm meet in the fallopian tube to form a fertilized egg, which then travels through the fallopian tube into the uterine cavity for implantation. If you do not get your period when it is due this month, you can have a blood test for HCG to determine if you are pregnant. However, sometimes the growth and development of the follicle does not go so well for various reasons. Some women have early follicle recruitment and selection, which is reflected in a shorter menstrual cycle; some women have follicles that are less than 18mm in size before they are expelled; and some women have no follicle growth and development during their menstrual cycle, which is called anovulation. At this time, it is necessary to consider the use of medications to help them so that the follicles can grow and develop normally. In the process of ovulation promotion, the commonly used ovulation drugs are clomiphene and letrozole, which have different mechanisms to promote ovulation, but they all share the same goal: by adjusting the hormones in the body, the follicles that would otherwise grow abnormally are recruited and selected to enter the normal growth track and mature. Because each person has different sensitivity to the drug and there are individual differences, some women will have 2 or more follicles after ovulation, but this is not an early consumption of follicles for later use. As mentioned earlier, normally, a batch of follicles will be raised each cycle, but eventually only one follicle matures and the others are occluded. During the ovulation promotion process, the follicles that would otherwise be atretic are only fully utilized to keep them from atreting and allow them to grow and mature. Therefore, ovulation promotion does not lead to premature ovarian failure.