title: Changes in shear wave speed pre- and post-induction of labor: a feasibility study.
abstract: OBJECTIVE
  To explore the feasibility of using shear wave speed (SWS) estimates to detect differences in cervical softening pre- and post-ripening in women undergoing induction of labor.
  
  
  METHODS
  Subjects at 37-41 weeks' gestation undergoing cervical ripening before induction of labor were recruited (n = 20). Examinations, performed prior to administration of misoprostol and 4 h later included Bishop score, transvaginal ultrasound measurement of cervical length, and 10 replicate SWS measurements using an ultrasound system equipped with a prototype transducer (128 element, 3 mm diameter, 14 mm aperture) attached to the clinician's hand. Subjects were divided into two groups, 'not-in-labor' and 'marked-progression', based on cervical evaluation at the second examination. Measurements were compared via individual paired hypotheses tests and using a linear mixed model, with the latter also used to compare groups. Spearman's rank correlation coefficient was used to compare SWS with Bishop score. The linear mixed model can take into account clustered data and accommodate multiple predictors simultaneously.
  
  
  RESULTS
  The Wilcoxon signed-rank paired test established a significant difference in pre- and post-ripening SWS, with mean SWS estimates of 2.53 ± 0.75 and 1.54 ± 0.31 m/s, respectively (P < 0.001) in the not-in-labor group (decrease in stiffness) and 1.58 ± 0.33 and 2.35 ± 0.65 m/s for the marked-progression group (increase in stiffness). The linear mixed model corroborated significant differences in pre- and post-ripening measurements in individual subjects (P < 0.001) as well as between groups (P < 0.0001). SWS estimates were significantly correlated with digitally-assessed cervical softness and marginally correlated with Bishop score as assessed by Spearman's rank correlation coefficient.
  
  
  CONCLUSIONS
  In-vivo SWS estimates detected stiffness differences before and after misoprostol-induced softening in term pregnancies. This ultrasonic shear elasticity imaging technique shows promise for assessing cervical softness.
authors.affiliation: Medical Physics Department, University of Wisconsin, Madison, WI, USA.
authors.forename: L C
authors.initials: LC
authors.lastname: Carlson
authors.affiliation: Division of Maternal Fetal Medicine, Intermountain Healthcare, Murray, UT, USA.
authors.forename: S T
authors.initials: ST
authors.lastname: Romero
authors.affiliation: Biomedical Engineering Department, Duke University, Durham, NC, USA.
authors.forename: M L
authors.initials: ML
authors.lastname: Palmeri
authors.affiliation: Medical Physics Department, University of Wisconsin, Madison, WI, USA.
authors.forename: A
authors.initials: A
authors.lastname: Muñoz Del Rio
authors.affiliation: Division of Maternal Fetal Medicine, Intermountain Healthcare, Murray, UT, USA.
authors.forename: S M
authors.initials: SM
authors.lastname: Esplin
authors.affiliation: Biomedical Engineering Department, Duke University, Durham, NC, USA.
authors.forename: V M
authors.initials: VM
authors.lastname: Rotemberg
authors.affiliation: Medical Physics Department, University of Wisconsin, Madison, WI, USA.
authors.forename: T J
authors.initials: TJ
authors.lastname: Hall
authors.affiliation: Medical Physics Department, University of Wisconsin, Madison, WI, USA.|Maternal Fetal Medicine Department, Intermountain Healthcare, Provo, UT, USA.
authors.forename: H
authors.initials: H
authors.lastname: Feltovich
mesh_terms: D020070:Cervical Ripening / Q000502:physiology; D002584:Cervix Uteri / Q000000981:diagnostic imaging*; D005240:Feasibility Studies; D005260:Female; D006801:Humans; D007751:Labor, Induced / Q000379:methods*; D016595:Misoprostol / Q000627:therapeutic use; D010120:Oxytocics / Q000627:therapeutic use; D011247:Pregnancy; D014463:Ultrasonography
chemical_list: D010120:Oxytocics; D016595:Misoprostol
keywords: cervix; induction of labor; shear wave speed