Thin endometrium will lead to hypomenorrhea，infertility and recurrent pregnancy loss and there are few effective methods to increase the endometrial thickness and improve the fertility outcomes. Patients with thin endometrium will be divided into three groups and receive estrogen therapy, stem cell therapy and growth factor therapy respectively. This randomized controlled clinical study is carried out to explore the optimal treatment method and best indications for thin endometrium.

Inclusion Criteria:

1.Patients with thin endometrium (4mm≤ EMT <7mm )or scarred endometrium (scarred area≤70%) which is nonresponsive to estrogen stimulation 2.Infertile patients with clear fertility desires 3.20-42 years old 4.Normal ovarian function or with frozen embryos 5.Willing to participate in follow-up

Exclusion Criteria:

1. Endometrial thickness <4mm or scarred endometrial area>70%
2. Uterine cavity out of shape and the cavity depth<6.5mm
3. Abnormal chromosome karyotype
4. Uterine diseases including large intramural myomas, severe endometriosis, severe adenomyosis, severe congenital uterine malformations, endometrial tuberculosis, vaginitis and endometritis
5. Systemic diseases: hypertension, diabetes, and so on
6. Contraindications to pregnancy
7. Contraindications to hormone replacement therapy
8. Medical history of pelvic tumors or receiving pelvic radiotherapy 9 .Involved in other clinical studies

10. Unable to adhere to the follow-up

female