Transperineal ultrasound assessment of maternal pelvic floor at term and fetal head engagement

Abstract

Objectives To evaluate the association between pelvic floor dimensions in nulliparous women at term and fetal head engagement, as assessed by transperineal ultrasound. Methods This was a prospective observational study of nulliparous women at term. Before the onset of labor, transperineal ultrasound was used to measure the anteroposterior diameter (APD) of the levator hiatus and the angle of progression (AoP) at rest, on maximum pelvic floor muscle contraction and on maximum Valsalva maneuver (before and after visual feedback). We assessed the correlation between pelvic floor static and dynamic dimensions (levator hiatal APD and levator ani muscle coactivation) and AoP, which is an objective index of fetal head engagement. Results In total, 282 women were included in the analysis. Among these, 211 (74.8%) women had a vaginal delivery while 71 (25.2%) had a Cesarean delivery. AoP was narrower in the Cesarean‐delivery group at rest, on maximum pelvic floor muscle contraction and on maximum Valsalva, whereas no differences in levator hiatal APD were found between the two groups. We found a negative correlation between levator hiatal APD at rest, on maximum pelvic floor muscle contraction and on maximum Valsalva and the duration of the second stage of labor. There was a positive correlation between AoP and levator hiatal APD on maximum Valsalva maneuver after visual feedback (r = 0.15, P = 0.01). Women with levator ani muscle contraction on Valsalva maneuver (i.e. coactivation), both pre and post visual feedback, had a narrower AoP at rest and on maximum Valsalva. After visual feedback, women with levator ani muscle coactivation had a longer second stage of labor than did those without (80.8 ± 61.4 min vs 62.9 ± 43.4 min (P = 0.04)). Conclusions Smaller pelvic floor dimensions and levator ani muscle coactivation are associated with higher fetal head station and with a longer second stage of labor in nulliparous women at term. Copyright © 2020 ISUOG. Published by John Wiley & Sons Ltd.

The dynamic change of the anteroposterior diameter of the levator hiatus under Valsalva maneuver at term and labor outcome

“…16,20 Smaller pelvic floor dimensions were found to be associated with a longer second stage of labor, whereas the relationship between pelvic floor dimensions and the mode of delivery is less clear with conflicting data. [15][16][17]21,22 The proportional change of the ADP of the levator hiatus has been found to be a reproducible -----) indicator of pelvic floor contraction. 10 To the best of our knowledge, this is the first study to assess the significance of the proportional change of APD as measured by TPU and labor outcome.…”

“…Moreover, pelvic floor muscle relaxation seems essential for childbirth. LAM coactivation was recently found to be associated with longer second, active second stage of labor and with less engaged fetal head at term 15,17,22 . In a recent study conducted on women undergoing vacuum delivery, LAM coactivation was assumed to be the cause of lack of fetal head descent with maternal pushing 23 …”

Fetal head progression and regression on maternal pushing at term and labor outcome

“…The authors speculated that fetal head regression on Valsalva maneuver may be due the phenomenon of pelvic floor contraction rather than relaxation on Valsalva, known also as levator ani muscle coactivation 45,46 . Levator ani coactivation was found previously to be associated with a less engaged fetal head at term and with a longer second stage of labor 42,43,47 . However, fetal head regression on maternal pushing before the onset of labor has not been studied previously.…”

The usefulness of ultrasound before induction of labor

“…[78][79][80][81] Furthermore, independent groups studied the behavior of the levator ani muscle on maximal Valsalva in pregnant women on transperineal ultrasound scanning. [79][80][81][82] The antero-posterior diameter of the levator hiatus can be assessed, quantitatively, using two-dimensional transperineal ultrasound where it is measured in the mid-sagittal view as the distance between the inferior border of the symphysis pubis to the anterior border of the puborectalis muscle. 83 Levator hiatus can also be used reliably with volumetric transperineal ultrasound assessment.…”