In this prospective, multicenter, large-scale study，the investigators wish to examine the accuracy of several three-dimensional ultrasound anatomical and vascular parameters in diagnosing IUA when compared to the gold standard of hysteroscopy，and to assess the value of 3D US applying in prognosis of intrauterine adhesions.

1. Study Design This is a prospective, multicenter, large-scale diagnostic testing. We use hysteroscopy finding as standard reference.
2. Study population 600 patients from three tertiary hospitals suspected of having IUA will be prospectively recruited. Thorough assessment including previous reproductive and surgical history as well as menstrual pattern will be performed.
3. Study Procedure 3.1 Diagnosis

IUA will be diagnosed in coronal plane, based on a suggestion reported by a Taiwanese study. The morphological characteristics of the endometrium suggesting IUA include as follow:

• marginal irregularity (in coronal plane)
• defects (interrupted endometrial line)
• obliteration (undetectable endometrium suggesting extensive adhesion)
• fibrosis or calcification (hyperechoic lesion without posterior shadowing, or with posterior shadowing) 3.2 Ultrasound
• Transvaginal Ultrasound will be performed in luteal phase.
• Using E10 Voluson GE with 3D/4D TV probe.
• Scan and rendering will be performed in a standardized technique (omniview mode).
• Several parameters will be measured including endometrial volume, uterine volume, vascularization (VI FI VFI).

3.3 Hysteroscopy

• Hysteroscopic exam will be used as the gold standard for the diagnosis of intrauterine adhesions.
• hysteroscopy will confirm the presence, extent, and morphological characteristics of adhesions and the quality of the endometrium.

3.4 Surgical technique

• Hysteroscopic surgery will be performed in a standardized manner.
• The severity and extent of intrauterine adhesions will be scored according to different classification systems. (ESGE/AFS/China consensus)
• a Foley-catheter filled with 3.0ml normal saline will be inserted into the uterus for 5-7 days after surgery.

3.5 Postoperative treatments

• All subjects will be treated with Hormone therapy for at least 8 weeks
• A second-look hysteroscopy will be carried out 4 weeks after surgery, a third-look hysteroscopy will be carried out 12 weeks after surgery
• A second-look 3D US will be carried out in luteal phase after two menstrual peroid postoperatively.

3.6 Follow up

• Follow-up styles: the doctor's outpatient review, telephone, WeChat and so on.
• Follow-up time:3 months, 6months, 12 months after the operation.
• Follow up the results of hysteroscopy and 3D US at 3 months after the operation and the menstrual improvement at 6months after the operation and pregnancy outcomes at 12 months after the operation

Inclusion Criteria:

• women aged 20-40
• oligomenorrhea or amenorrhea
• BMI 18-30
• regular menstruation
• written consent obtained

Exclusion Criteria:

• Hypothalamic amenorrhea, pituitary amenorrhea and ovarian amenorrhea
• Patients with uterine fibroids, adenomyosis, uterine malformation and endometrial polyps
• Patients with uterine artery embolization
• History of endometrial hyperplasia
• Irregular menstruation
• Patients with severe complications
• Patients with hypoovarian function

600 patients from three Tertiary hospitals suspected of having IUA will be prospectively recruited