Clinical Study of Umbilical Cord Mesenchymal Stem Cells Combined With Collagen Scaffold in the Treatment of Thin Endometrium

Inclusion Criteria: 1. According to the GCP regulations, obtain the informed consent of the subject, volunteer for the test, and have signed the informed consent form. 2. Women aged 20-40 years with fertility requirements 3. Infertility patients who are treated in this hospital 4. After more than 2 times of hysteroscopic adhesion separation surgery, the uterine cavity morphology has basically returned to normal. The patient has a normal menstrual cycle or an estrogenic dose of 6 mg per day, and the highest thickness of the endometrium is 5.5 mm in 6 cycles by ultrasound. 5. or receive adjuvant reproductive treatment, the endometrial thickness is less than 5.5mm for unknown reasons, the treatment of estrogen, colony stimulating factor, aspirin, sildenafil and other drugs up to 8mg / day is invalid. 6. HBVAg negative, HCV negative, HIV negative, syphilis negative 7. Normal bone marrow morphology, normal blood routine 8. Previously failed to receive relevant stem cell therapy Exclusion Criteria: 1. Those who cannot accept the treatment observation process required by the test 2. There are contraindications for hysteroscopic surgery; 3. congenital uterine malformation; severe adenomyosis; uterine fibroids that may affect embryo implantation; the investigators judged that there are other uterine factors that are not suitable for embryo implantation 4. Patients with chromosomal abnormalities 5. contraindications to estrogen therapy; systemic diseases such as thrombosis, cardiopulmonary disease, hematopoietic diseases, malignant tumors, etc. 6. Patients without fertility requirements