Exclusion criteria
First, each patient’s history was reviewed. Patients who met one of the following criteria were excluded: (1) a previous history of total or subtotal hysterectomy or cervical excision; (2) previous pelvic floor surgery for prolapse or urinary incontinence; (3) a history of prolapse or urinary or faecal incontinence; (4) pregnancy with a gestational age ≥ 8 weeks or within 12 months after delivery; and (5) malformation of the female genital tract, such as Mayer-Rokitansky-Küster-Hauser syndrome, although uterine mediastinum was not excluded. Then, the MR images and MRI reports were reviewed. Patients who met one of the following criteria were excluded: (1) a maximum uterine diameter ≥ 7 cm, such as multiple uterine fibroids or adenomyosis; (2) any mass or cysts in the pelvis with a diameter ≥ 6 cm, such as fibroids, ovarian cysts, or hydrosalpinx; (3) any mass or cysts in the cervix or the cervical canal with a diameter ≥ 2 cm; (4) any mass or cysts on the vaginal wall, in the vaginal lumen, or in the area around the vagina with a diameter ≥ 2 cm; (5) a maximum diameter of the rectum ≥ 3 cm or maximum bladder diameter ≥ 6.5 cm on any sagittal images; and (6) poor visibility of the anatomic structures of the landmarks. Finally, the pelvic examination records were carefully reviewed, and any patients with POP were excluded. If surgical treatment was conducted in our hospitals, the corresponding record was also reviewed. Patients with dense, extensive adhesions between the uterus and abdominal wall suggestive of an obvious change in the position of the uterus were excluded.