Open Access

Aim: The aim of this study is to utilize the niche measurement guidelines outlined by Jordans et al. in order to establish normal values and accurate description of caesarean section scars in a normal population. After defining the normal distribution, abnormal pregestational scar characteristics will be identified for predicting adverse pregnancy outcomes. Methods: This is a prospective observational multicenter clinical study where women with a history of only one caesarean section and yet open family planning are enrolled. The uterine length, cervical length, niche length, niche depth, niche width, residual myometrial thickness, endometrial thickness, scar to internal os distance, anterior myometrial thickness superior and inferior to the scar and the posterior myometrial thickness opposite the scar, superior and inferior to it are measured in a pregestational uterus. The lower uterine segment is measured over a length of 3 cm during subsequent pregnancy and followed up until delivery. Results: Data from 500 patients will yield normal distribution curves for all predefined measurements. Establishing a correlation between deviations from the normal measures and adverse events would be instrumental for counseling women regarding subsequent pregnancy and mode of delivery. Conclusion: This study will demonstrate the changes of the post-caesarean scar from a non-pregnant uterus until delivery and can confirm the importance of the scar characteristics in predicting pregnancy outcome.

Purpose: We aim to describe the sonographic uterine anatomy after a cesarean section (CS), test the reproducibility of predefined measurements from the BSUM study, and report the distribution of these measurements. Methods: This is a descriptive observational study where 200 women with a history of only one CS were recruited 12–24 months postoperatively. A 5–13 MHz micro-convex transvaginal transducer was used for the acquisition of volumetric datasets for evaluating the CS scars. We defined 15 distinct measurements including the residual myometrial thickness (RMT). RMT ratio was calculated as a percentage of RMT to the assumed pre-cesarean anterior uterine wall thickness. A P value below 0.05 is utilized for significant statistical analysis. Results: Patients were included on average 18.5 months post-cesarean. The uterus was anteflexed in 82.5% and retroflexed in 17.5%. Myometrial defects at the site of CS manifest in two forms, either as a niche or as fibrosis. Patients are classified into four groups: those with isolated niches (45%), combined niches and fibrosis (38.5%), isolated fibrosis (11%), and lacking both (5%). The median RMT ratio for these groups was 63.09, 40.93, 59.84, and 100% with a standard deviation of 16.73, 12.95, 16.59, and 0, respectively. The interclass correlation coefficient (ICC) remained above 0.9 for all distinct measurements among these groups except for those of RMT, where ICC varied between 0.47 and 0.96. The RMT ratio shows a constant ICC at 0.94 regardless of the group. Conclusion: The post-cesarean uterus is often anteflexed, and a myometrial loss of about 50% is normally expected. The pattern of this loss is in the form of a predominantly sharp-edged and echogenic niche, fibrosis, or a combination of both. The proposed RMT ratio takes these changes into consideration and results in a reproducible quantification. We hypothesize that different adverse outcomes could be attributed to the different scar patterns.

Objective: To assess the effect of cesarean section (CS) timing, elective versus unplanned, on the residual myometrial thickness (RMT) and CS scars. Methods: This is a prospective single-blinded observational cohort study with 186 observations. Patients indicated to undergo first singleton CS were preoperatively recruited. Exclusion criteria were history of repeated CS, vertical hysterotomy, diabetes, and additional uterine surgeries. Sonographic examination was performed for assessing the RMT ratio, the presence of a niche, fibrosis, and the distance from the scar to the internal os (SO) 1 year after CS. Power analysis was performed with 0.05 α, 0.1 β, and all statistical analyses were conducted with Stata®. Results: Wilcoxon rank-sum test for the association between CS timing, RMT ratio and SO showed Z values of −0.59 and −4.94 (P = 0.553 and P < 0.001), respectively. There was no association between CS timing and niches and fibrosis (P > 0.99 and P = 0.268, respectively). Linear regression between SO and the extent of cervical dilatation showed a −0.45 β (95% confidence interval −0.68 to −0.21) and a 10.22-mm intercept (P < 0.001). Conclusion: RMT is independent of the timing of CS, but the SO distance shows a negative linear relationship with the cervical dilatation.