Long-term Level III Measures on 3D Endovaginal Ultrasound After Vaginal Birth

Objectives: The perineal complex - levator ani muscles, perineal membrane, and perineal body - is not well studied but important in maintaining genital hiatal closure. An enlarged hiatus after vaginal delivery increases the risk of prolapse development later in life. All components of the perineal complex can be evaluated on 3D endovaginal ultrasound. The purpose of this study was to evaluate how hiatal measures change 6 weeks, 6 months, and 5+ years postpartum.

Methods: Women at high risk for pelvic floor injury who previously participated in a pelvic floor study after their first vaginal birth were recruited to participate at approximately 5 years out from delivery. Participants were included for analysis if they had a 3D endovaginal ultrasound performed at all three time points (6 weeks, 6 months, 5+ years postpartum). Participants underwent POP-Q and 3D endovaginal ultrasound exams. Participant's measures at 6 weeks, 6 months, and 5+ years were evaluated on their 3D endovaginal ultrasound images. The urogenital hiatus (UGH) diameter, UGH area, levator hiatus (LH) diameter, and LH area were measured using 3DSlicer software (Figure 1).

Results: Eight participants were included in the analysis (9 were eligible, 1 was excluded due to poor image quality). Participants were an average age of 37.9 years and 50% of the cohort had a subsequent birth after original study participation. None participants reported symptoms of vaginal prolapse. All participants had stable POPQ GH measures from 6 weeks to 6 months, while 62% (n=5) of participants had a POPQ GH that increased from 6 months to 5+ years (Figure 2). Of the 24 ultrasounds available for evaluation, from the 8 included women, 5 images did not capture the perineal body well enough for evaluation (probe too deep; inadequate contact between probe, gel, and tissue leading to poor image quality). All participants with included UGH measurements had an increase in UGH size from 6-month to 5+ years (diameter: 3.4 ±0.4 v 4.1 ±0.7 cm, area: 8.9±1.6 v 14.1 ±3.0 cm). All participants had enlarging LH measures (diameter: 4.3 ±0.5 v 5.6 ±0.6 cm, area: 12.1 ±1.7 v 19.0 ±2.8 cm).

Conclusions: The perineal complex can be evaluated using 3D endovaginal ultrasound, however standardized methods are needed to ensure superficial structures such as the perineal body can be visualized. Enlarging hiatal measures 5 years after first vaginal delivery were noted in this high risk group.

Figure 1. (a) Midsaggital image (b) axial image at level of LH (c) axial image at level of GH. PS: pubic symphysis; PB: perineal body; EAS: external anal sphincter; U: urethra; V: vagina; A: anus; PA: pubic arch; PVM: pubovisceral muscle; blue: levator area; orange: urogenital hiatus area