The endothelium is the soil in which the embryo is planted as well as develops, and plays an important role in the process of pregnancy. Clinical monitoring of the endothelial morphology, thickness and other indicators are used to guide treatment and embryo transfer. When monitoring ovulation in outpatient clinic, many people will ask: Why is my lining so thin? Can drinking soy milk and eating black beans make the lining grow? Under normal circumstances, the endometrium thickens with the development of follicles and the rise of estrogen, while some people’s endometrium is always very thin, and it cannot be thickened by follicular development or even external medication, which is called refractory endometrium. At present, there is no uniform standard for the thickness of endometrium in the international arena, and most of the opinions are inclined to be 7mm, and there is even no definite value for the thickness of the endometrium that is the most suitable for pregnancy. In 1997, Remohà et al. and in 2011, Cai et al. found that endometrial thicknesses ranging from 5 mm to more than 15 mm had similar chances of success, and even endometrial thicknesses of less than 5 mm have been reported in cases of successful pregnancy and delivery. Today, let’s talk about the causes of thin endometrium and the treatments available at this stage. Causes of thin endometrium The most common cause of thin endometrium is surgical adhesion of the uterine cavity. The repair process of endometrial damage will lead to the formation of fibrous connections between the endometrium. 90% of the cases of uterine adhesion are the result of scraping of the uterus after miscarriage, which manifests itself as a low menstrual flow and failure of embryo implantation, and also leads to recurrent miscarriage, preterm labor, and placenta adhesion. Similarly, various intrauterine operations including electrosurgery and postoperative uteroplasty such as mediastinum, bicornuate uterus etc. may cause adhesions in the uterine cavity leading to thinning of endometrium. In patients with recurrent miscarriages, it has been found that chronic endometrial inflammation may be the culprit. In these patients, hysteroscopy is valuable for diagnosis, and compared with untreated patients, patients treated with regular, adequate, and sufficient courses of antibiotics have a significantly better prognosis, with a significantly higher rate of implantation of the embryo, and combined with Chinese medicine treatments, such as acupuncture, they also have a favorable outcome. In some malignant tumors, radiotherapy can lead to smaller uterine cavity, thinner endometrium, reduction of uterine length as well as impaired endothelial blood flow. Endothelial damage caused by radiotherapy is dose- and age-dependent, and the younger the age, the more severe the damage and the less likely the recovery. The female reproductive tract develops from the molluscum contagiosum in the early embryonic stage and develops into the fallopian tubes, the uterus, and the upper part of the vagina, which usually occurs at 20 weeks of embryonic development. The incidence of abnormal molluscum contagiosum development is 5%, and most of the molluscum contagiosum develops into the mediastinum uterus, followed by the bicornuate uterus, which is difficult to diagnose because it develops due to a variety of reasons. Abnormal expression of some genes such as homologous frameshift genes (HOX) can also cause developmental abnormalities. The following treatments are currently recognized and largely proven to improve thin endometrium. In conclusion, the diagnosis and treatment of thin endometrium, especially refractory endometrium, has always been a difficult problem. The above treatments are not effective for everyone, and dietary therapy has not been proved to have a significant effect; hysteroscopy is necessary, but there is a lack of effective means of endometrial function testing and evaluation indexes.