Do some levator avulsions improve over time?

Objective: To determine whether the sonographic appearance of levator ani muscle avulsion after vaginal birth can improve significantly over the first few years postpartum.

Methods: This was a retrospective study of women seen in the context of two prospective perinatal imaging studies. All subjects had undergone an interview, clinical examination and four-dimensional translabial ultrasound on average 4.3 months and 3.1 years postpartum. Volume datasets were analyzed at a later date, with the examiner blinded against all other data. The number of abnormal slices at both timepoints was compared using the Mann-Whitney U-test. Patients in whom findings had changed over time were reviewed separately, in parallel, in order to reduce the impact of differences in slice location and imaging settings. The symmetry test was used to analyze changes between the two postnatal visits.

Results: Of 1148 women recruited originally, 315 attended at least two postnatal visits. Forty-two were excluded, leaving 273 women for the final analysis. The mean time of first follow-up was 4.3 (range, 2.6-9.8) months after their first birth and the mean time of last follow-up was 3.1 (range, 1.4-8.0) years postpartum. Cohen's κ for the category of avulsion (normal, partial avulsion and full avulsion) at the two assessments was 0.89, with agreement in 97% (264/273) of cases. At the first visit, full levator ani muscle avulsion was diagnosed in 20, partial avulsion in 32 and no avulsion in 221 women. While seven partial avulsions appeared sonographically normal at the second visit, there were no statistically significant changes in avulsion category between visits (P = 0.4).

Conclusions: Tomographic pelvic floor imaging obtained 3-10 months after childbirth may be used as a proxy for long-term outcomes. Ultrasound findings at a mean of 3.1 years postpartum showed 97% agreement with findings obtained on imaging at a mean of 4.3 months postpartum. There was a non-significant reduction in abnormal slices at the second follow-up visit, affecting at most 3/12 slices. This may be explained by compensatory hypertrophy of the remaining intact muscle. Sonographic normalization of full levator ani muscle avulsion was not observed. © 2024 International Society of Ultrasound in Obstetrics and Gynecology.