Impact of levator trauma on pelvic floor muscle function.

INTRODUCTION AND HYPOTHESIS: Levator trauma is common after vaginal delivery, either as macrotrauma, i.e., levator avulsion, or microtrauma, i.e., irreversible overdistension of the levator hiatus. The effect of microtrauma on muscle function is unknown. We tested the hypothesis that levator trauma is associated with reduced contractile function of the levator ani.
METHODS: Pregnant nulliparous women were recruited and seen before and after childbirth. All underwent an interview, a clinical examination including pelvic floor muscle (PFM) assessment using the Modified Oxford scale (MOS) [as an optional component] and translabial ultrasound. Sonographic and clinical parameters of PFM function were assessed before and after childbirth.
RESULTS: Out of 560 women, 446 returned at a median of 5 months after childbirth and 433 were suitable for analysis. There was a significant reduction in all measures of PFM function except for MOS. Change in MOS was associated with delivery mode [analysis of variance (ANOVA) P = 0.006). Forty-seven (15 %) vaginally parous women were diagnosed with levator avulsion, which was associated with a reduction in PFM contractility on sonographic parameters and MOS. However, only clinical assessment reached statistical significance. Sixty-five of 312 (21 %) women were diagnosed with microtrauma. We found no evidence of impairment in PFM contractility on ultrasound, but there was a statistically significant reduction in MOS.
CONCLUSIONS: Both levator avulsion (macrotrauma) and irreversible overdistension (microtrauma) are associated with reduced contractile function. This effect is more easily detected by palpation than by sonographic indices of levator function.