Sonographic Features Of Lower-segment Cesarean Section Scars In Second-Third Trimester Pregnant Women With Previous Cesarean Delivery

Objective:To examine the sonographic features of lower-segment cesarean section scars in pregnant women with previous cesarean delivery.Material and Methods:This is a prospective study. Sonographic examination was performed on365second-trimester pregnant women, including249pregnant women with previous cesarean delivery,77nulliparas, and39pregnant women who had1or more childbirths with unscarred uteri. Both the transabdominal scan and the transperineal scan were performed for the every case. Measurements were obtained with cursors at the interface of the urine-bladder and the amniotic fluid-decidua, then assess the sonographic appearance and compare the thickness of the lower uterine segment. In the cesarean group, the sonographic findings were correlated with the delivery outcome and intraoperative appearance. Results:1. In the most cases, the sonographic examinations are successful. On ultrasound, the lower uterine segment appears as a three layered structure consisting of the chorioamnionitic membrane with a decidualized endometrium, the middle layer of the myometrium, and the uterovesical peritoneal reflection juxtaposed to the muscularis and mucosa of the baldder on the outer side.2. During the444times examinations, their transabdominal sonographic images were better than their transperineal images. The agreement between the different scan methods was satisfied (correlation coefficient0.943), while the results from the transabdominal scaning were greater than the results from the transperineal scaring (p=0.000).3. In the study group,43times examinations (11.7%) the scar location were identified. During the other324times examinations, the lower uterine segment were scanned in the sagittal section to localize the thinnest area and measured.4. With the gestational age increasing, the measurements of each group cases were gradually thinning.5. During the different gestational ages, the uterine segment in the study group was the thinnest and the result of the multip group was the thickest.6. In the study group, all the cases were repeated the cesarean. During the surgery,144cases were confirmed having the well-developed lower uterine segment,83cases were confirmed having the thin lower uterine segment,5cases were confirmed having the Translucent lower segment (the content were visible). There was no uterine rupture case.7. During the509times examinations, the color doplor flow signs rate in thinnest area of the lower uterine segment was26.7%. Conclusion:1. In the most cases, the sonographic examinations are successful, and their transabdominal sonographic images were better than transperineal images. While transperineal scaning were necessary for the cases whose thinnest area in the lower uterine segment were near to the cervix.2. With the gestational age increasing, the lower uterine segment were gradually thinning in each group. And the uterine segment in the study group was the thinnest and the result of the multip group was the thickest.3. Using the cut-off value of1mm in assessing women with previous CS, we can determine the degree of LUS thinning. When the lower uterine segment＜1mm, we should alarm for the rupture.4. Although the lower uterine segment measurement has potential to predict uterine rupture, but we still cannot use it confidence in the management of vaginal birth after caesarean section.