OP34.08: Building a wellness reference biometry of levator hiatus of Chinese women using 3D ultrasound imaging

To establish the normal range of the biometry of levator hiatus in nulliparous, multiparous and postmenopausal Chinese women using 3D perineal ultrasound. We enrolled 1.051 healthy Chinese women, including 513 nulliparous, and 538 multiparous (408 premenopausal and 130 postmenopausal. None of the subjects had any pelvic organ prolapse or symptom of pelvic floor dysfunction. The 3D ultrasound volume was sampled and the size and form of hiatus were measured in the axial plane set by interio-inferior edge of symphysis pubis, anal-rectal junction and urethra. In nullparous subjects, the anteroposterior diameter, lateral diameter, area and circumference of the levator hiatus were 5.40 ± 0.60 cm, 3.74 ± 0.43 cm, 14.06 ± 2.38 cm2 and 14.51 ± 1.23 cm, which were significantly smaller than multiparous subjects (5.57 ± 0.63 cm, 3.90 ± 0.46 cm, 15.52 ± 6.12 cm2, 15.03 ± 1.30 cm, respectively, all four with P < 0.05). Interestingly, we found lateral diameter, area and circumference of subjects who had vaginal delivery were significantly larger than those who had caesarean section (3.97 ± 0.47 cm vs. 3.78 ± 0.42 cm by lateral diameter, 16.17 ± 2.33 cm2 vs. 14.43 ± 2.11 cm2 by area, 15.23 ± 1.42 cm vs. 14.75 ± 1.13 cm by circumference, all three with P < 0.05). Moreover, the size of levator hiatus correlated with the times of vaginal delivery (correlation = 0.75). In multiparous postmenopausal subjects, the mean size of levator hiatus was 5.80 ± 0.99 cm by anteroposterior diameter, 3.94 ± 0.41 cm by lateral diameter, 16.41 ± 4.29 cm2 by area and 15.59 ± 2.14 cm by circumference, none of which was statistically significant compared to the multiparous premenopause group. We have collected morphological parameters of levator hiatus from a large set of healthy women with different reproductive history, which will serve as an important reference for studying levator hiatus related diseases in the future.