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

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