Three-dimensional ultrasound imaging of the pelvic floor: the effect of parturition on paravaginal support structures.

OBJECTIVE: It is assumed that support of the female urethra and bladder is maintained by paraurethral and paravaginal fascial structures, with hypermobility resulting from delivery-related trauma. This study used three-dimensional translabial ultrasound to assess these structures and document peripartal changes. DESIGN: A clinical observational pilot study was performed on 26 nulliparous women recruited in the third trimester of pregnancy. They underwent translabial two- and three-dimensional ultrasound. Twenty-three women were again seen 2-5 months postpartum. The assessor was blinded against two-dimensional ultrasound and delivery data. Vaginal tenting was rated as being present, indeterminate or absent at each of three levels, and was correlated with bladder neck descent (BND) and urethral rotation on Valsalva maneuver. RESULTS: Tenting was visible at all levels in 21 of 26 women antepartally. In three women tenting was absent on one level; in two cases tenting was rated indeterminate. There was no significant difference in BND between women with visible tenting and those without. The BND range for women with intact tenting was 5.4-41.6 mm. Twenty-one of the 26 women were included in the postpartum analysis. Of these, obvious peripartal changes were documented in five. Loss of tenting did not correlate significantly with changes in BND. CONCLUSIONS: Most nulliparous women showed evidence of intact paravaginal support structures. Tenting occurred in women with widely varying BND, implying that excess bladder neck mobility may be due to increased fascial compliance. Postnatally, fascial disruption was suspected in a minority of patients only. In some women delivery-related changes may be due to attenuation rather than disruption of structures.