To explore the risk factors of endometrial lesions in patients with abnormal uterine bleeding and establish prediction models which can discriminate between different endometrial etiologies of abnormal uterine bleeding(AUB).

Inclusion Criteria:

• 1) non-pregnancy related abnormal uttering bleeding（AUB） in women of 18-60 years old; 2)women who had indications for hysteroscopy and endometrial histology in the study period

Exclusion Criteria:

• 1) postmenopausal women, 2) AUB due to other causes such as hormones or medications, coagulation disorders, and vascular malformation of the uterus; 3) final diagnosis outside the scope of this study.

This cross-sectional study was approved by the Institutional Ethics Committee and conducted in the Beijing Friendship Hospital, Capital Medical University in China