Strain ratio elastography of the uterine cervix and prediction of successful labor induction

Abstract

Background

Before labor induction, the uterine cervix is often evaluated by the Bishop score, or a modified Bishop score, to predict the duration and success of induction. However, more objective methods are wanted. Strain ratio elastography is a technique that evaluates the elastic modulus of a tissue. Using strain ratio elastography in combination with a reference material enables quantitative elastography of the uterine cervix.

Objective

To evaluate the associations between the apparent elastic modulus of the cervical tissue assessed by strain ratio elastography and the cervical dilation time after labor induction.

Methods

Twenty-two nulliparous pregnant women admitted for labor induction were included. A Bishop score, a cervical length measured by ultrasound and an elastic modulus evaluated by strain ratio elastography were obtained from all participants. Primary outcomes were cervical dilation time from labor induction to active labor and from active labor to full cervical dilation.

Results

The strain ratio was not associated with the time from labor induction to active labor R²: 0,024 (P = 0.492), but there was a small association between strain ratio and time from active labor to full cervical dilatation R²: 0.180, however not significant (P = 0.063). The cervical length was associated with time from labor induction to active phase R²: 0.134 (P = 0.003), but not with time from active labor to full dilatation R²: 0.015 (P = 0.610).

Conclusions

The results indicate a possible importance of the elastic modulus for predicting time from active labor to full cervical dilatation, whereas the cervical length seems to be of greater importance for time from labor induction to active labor.