Reducing pelvic floor injury by induction of labor

Abstract

Introduction and hypothesis: We hypothesized that elective induction of labor (eIOL) at 39 weeks is protective of levator ani muscle injury (LAMI) and is associated with decreased pelvic symptoms at 6 weeks postpartum compared to expectant management of labor.

Methods: Prospective cohort pilot study of uncomplicated, primiparous women with a singleton, vertex gestation enrolled immediately post-vaginal delivery (VD). Subjects were dichotomized into two groups based on labor management: eIOL without complication defined by the ARRIVE trial versus spontaneous VD between 39 weeks^0/7 and 42 weeks^5/7 or no indication for IOL prior to 40 weeks^5/7. The primary outcome was LAMI at 6 weeks postpartum as evidenced by any of the following ultrasound measures: (1) increased levator hiatal area (LHA) > 2500 mm², (2) increased elasticity index (EI, > 75th quartile) or (3) levator enthesis avulsion.

Results: Analysis represents 45/102 consented women from July 2019-October 2020 (eIOL n = 22 and spontaneous VD, n = 23). Neither maternal, clinical, sociodemographic characteristics nor pelvic symptoms differed between groups. Fewer women had LAMI as defined by the primary outcome with eIOL (n = 5, 23.8%) compared to spontaneous VD (n = 15, 65.2%), p = 0.008. Levator enthesis was more deformable (increased EI) with spontaneous VD as compared to the eIOL [10.66 (8.99) vs. 5.68 (2.93), p = 0.046]. On univariate logistic regression women undergoing spontaneous VD had unadjusted OR of 6.0 (1.6-22.5, p = 0.008) of sustaining LAMI compared to those undergoing eIOL.

Conclusions: Composite measures of LAMI though not pelvic floor symptoms were markedly increased in women undergoing spontaneous VD compared to those undergoing eIOL at 39 weeks.

Keywords: Birth injury; Elastography; Elective induction; Obstetric injury; Pelvic floor disorder; Transperineal ultrasound.

Fig. 1

CONSORT (Consolidating Standards of Reporting Trials) Diagram

Fig. 2

Primary outcome: composite pelvic floor injury was more common in the spontaneous delivery group. The primary outcome was composite marker for pelvic floor injury; a composite score of (1) increased LHA > 2500 mm², (2) decreased tissue modulus or increased elasticity index > 75% quartile or (3) presence levator avulsion on TPUS. Figure represents composite and individual dichotomous components. LHA = levator hiatal area

Fig. 3

Transperineal ultrasound axial plane images with urethra (U), vagina (V) and rectum (R) labeled. A Normal postpartum without LHA enlargement or injury. B Postpartum injury with left-sided levator avulsion (LA) and enlarged levator hiatal area (LHA)