Technique of sonographic assessment of lower uterine segment in women with previous cesarean delivery: a prospective, pre/intraoperative comparative ultrasound study

Abstract

Objective: The purpose of this study was: (A) to establish the effects of different ultrasound measurement methods (linear versus curved array) and measuring conditions [impact of pressure by fetal head/pelvis on the lower uterine segment (LUS)] during LUS-muscular-thickness measurement, (B) to introduce the intraoperative ultrasound measurement of LUS-muscular thickness (reference measurement method), and (C) to evaluate the correlation between different combinations of LUS-muscular-thickness measurement ultrasound techniques at birth planning and preoperative versus intraoperative measurements.

Methods: A prospective clinical observational study of women with the previous cesarean delivery was conducted. LUS-muscular thickness was measured: first at birth planning and second preoperatively using linear and curved probes (transabdominal) and an endocavitar probe (transvaginal), examined with and without pressure by fetal head/pelvis on LUS during measurement and third intraoperatively during repeat cesarean. Bland-Altman plots, paired t tests, Pearson's correlation coefficient, and scatter plots were used.

Results: Thirty-three women were included in the study (ultrasound measurements: n = 601). There was no systematic difference between LUS-muscular-thickness measurements with linear versus curved array (mean difference = 0.06 mm; p = 0.24; n_m = 133) but between measurements with pressure by the fetus versus without (mean difference = - 0.37 mm; p < 0.001; n_m = 243). The highest correlation coefficients were detected for the preoperative (at the day of cesarean section), transabdominal-vaginal approach combined ultrasound measurements versus the intraoperative ultrasound measurements of LUS-muscular thickness-as long as the measurements were made without pressure from the fetal head/pelvis on the LUS [0.86, p < 0.001, n = 24, 95% CI (0.70, 0.94)].

Conclusions: The systematic application of predetermined measuring conditions, standardized setup criteria improves the performance of LUS thickness measurement by ultrasound near term. CLINICALTRIALS.

Gov identifier: NCT02827604.

Keywords: Intraoperative measurement; Lower uterine segment; Myometrial thickness; TOLAC; Ultrasound; VBAC.