The incidence of endometriosis is increasing year by year, and the disease is usually seen in women of childbearing age, mostly in women aged 20-40. Endometriosis is closely related to infertility and is known as the “invisible killer” of infertility in women of childbearing age. The incidence of infertility among patients with endometriosis is 30% to 50%, which is 20 times higher than that of non-endometriosis patients. How does endometriosis cause infertility? Since pregnancy requires a “seed” (the ovaries are able to discharge an egg), a “clear road” (the pathway for the sperm to meet the egg and for the fertilized egg to be transported to the uterine cavity), and “fertile soil” (the endometrium and other embryos to grow), the endometrium is the most fertile place for pregnancy. The endometrium is the place where the embryo grows and develops.) Endometriosis causes infertility mainly because it affects the above mentioned links. Possible factors: 1. Mechanical factors: Patients with endometriosis often have pelvic adhesions. The causes of infertility in severe cases may be related to extensive adhesions of organs and tissues in the pelvic cavity that affect the discharge of eggs, weakened peristalsis of the fallopian tubes or even adhesions, resulting in the inability of the fallopian tubes to pick up eggs and the inability of fertilized eggs to run normally to the uterus. Endometriosis can be associated with a variety of ovarian abnormalities, such as abnormal LH peak, follicular development, anovulation, hyperprolactinemia, luteal insufficiency and luteinization syndrome of unruptured follicles (LUFS), the incidence of which is higher than that of non-endometriosis population. In case of LUFS, where the ovaries are anovulatory but the follicular cells appear luteinized, the patient has no possibility of conception because of anovulation, although the basal body temperature is biphasic and the endometrium shows secretory phase changes. There have been many reports in the literature confirming that the incidence of luteinization of unruptured follicles is significantly higher in patients with endometriosis compared to normal women, so infertility occurs more often. The number of LH receptors on follicles and luteal cells is significantly lower in patients with endometriosis than in normal women, resulting in insufficient hormone secretion from the corpus luteum during the luteal phase and affecting conception. 3. Autoimmune reaction: Lymphocytes in patients with endometriosis produce an anti-endometrial antibody, which can interfere with early fertilization egg transport and implantation, while the presence of endometriotic lesions in the abdominal cavity causes the accumulation of a large number of macrophages, which can engulf sperm and interfere with the division of fertilized egg cells, leading to infertility. Clinically, it has been found that even mildly affected patients with few pelvic endometriosis lesions and no obvious abnormalities in pelvic anatomy can be infertile. It may be related to this factor and pelvic inflammatory response. Endometriosis can affect early embryonic development, with abnormal corpus luteum function and abnormal intrauterine environment, interfering with early embryonic development and implantation, resulting in obstructed implantation and miscarriage. Clinically, the miscarriage rate of patients with endometriosis is higher than that of the general population. 5. Other causes: Patients with endometriosis experience deep painful intercourse during sexual intercourse, which more or less affects the patient’s mood and even inhibits ovulation. The causes of infertility due to endometriosis may be the result of multiple factors. If infertility in women of childbearing age is considered to be related to endometriosis, laparoscopic surgery is recommended as soon as possible. A lot of clinical practice shows that if endometriosis-related infertility is treated only with medication, it often fails to achieve the goal of pregnancy and wastes time, and it is advisable to conceive as soon as possible after surgery. “Of course, if you are old, have poor ovarian reserve function, fail to get pregnant as you wish after previous surgery, or have recurrent severe endometriosis, you can consider assisted reproductive technology to get pregnant, and applying drugs for 3 months before assisted reproductive technology can increase the chances of success.