Objective: To investigate the relationship between the previous cesarean scar thickness, previous cesarean scar defect and the occurrence of uterine rupture for pregnancy women after previous cesarean section and to predict the occurrence of uterine rupture in the third trimester for pregnancy women after previous cesarean section by analyzing the lower uterine segment (LUS) situation or quantitatively measure LUS myometrium thickness. Methods: A total of 154 pregnant women who have a prior cesarean from January 2015 to March 2016 were selected, all of them regularly did the prenatal examination in the pregnancy period and finally gave birth in hospital. By the transvaginal sonograph, the LUS myometrium thickness (transverse and longitudinal thickness) and the size of the previous cesarean scar defect were measured in the first trimester, the LUS myometrium thickness (longitudinal thickness) and qualitatively analysis LUS condition were measured in the third trimester. They were divided into two groups according to the pregnancy outcome: uterine rupture group (found in the cesarean operation or during the pregnancy) and without uterine rupture group (including the vaginal delivery women and those without uterine rupture in the cesarean operation period). The sensitivity and specificity of LUS myometrium thickness in the first trimester and the qualitative analysis LUS situation, the quantitative measurement of LUS myometrium thickness in the third trimester were compared in the prediction of occurrence of uterine rupture (dehiscence or complete rupture). Results: The group without uterine rupture included 134 women (6 vaginal delivery and 128 cesarean delivery), and the group with uterine rupture included 20 women (all of them cesarean delivery). The LUS myometrium thickness in the third trimester in the group without uterine rupture was (1.6±0.5) mm, and was (1.1±0.7) mm in the uterine rupture group (P= 0.004). There were no significant difference between two groups in the mean value of age, height, weight, the interdelivery interval, the LUS myometrium thickness (transverse and longitudinal thickness) in the first trimester. Qualitative analysis of LUS condition had higher specificity (99%), higher positive predictive value (92%), higher negative predictive value (94%) and slightly lower sensitivity (60%) than quantitative measure of LUS myometrium thickness in predicting uterine rupture. Conclusions: Measurement of the LUS myometrium thickness in the first trimester is helpful for predicting the occurrence of uterine rupture, so it is not necessary to terminate the pregnancy because of the thin LUS or the little prior cesarean scar defect in the first trimester. However it should be paid close attention to the LUS situation during the whole gestation. Qualitatively analyzing LUS situation is more meaningful than quantitatively measuring LUS myometrium thickness in predicting the uterine rupture in the third trimester.
目的： 探讨剖宫产术后再次妊娠孕妇妊娠早期剖宫产术后子宫瘢痕的厚度、剖宫产术后子宫瘢痕憩室（CSD）与发生子宫破裂的关系，并定性观察妊娠晚期子宫下段（LUS）肌层的连续性及测量其厚度以预测剖宫产术后再次妊娠孕妇发生子宫破裂的价值。 方法： 收集2015年1月至2016年3月在北京大学第一医院进行规律产前检查并分娩、既往有剖宫产术史的孕妇154例，超声测量其妊娠早期剖宫产术后子宫瘢痕的厚度（横切厚度及纵切厚度）、CSD大小及妊娠晚期LUS肌层的厚度（纵切厚度）及定性观察其连续性。根据妊娠结局将孕妇分为两组：子宫未破裂组（自然分娩或剖宫产术中未发现子宫破裂者）134例及子宫破裂组（剖宫产术中发现子宫不完全性破裂或妊娠期子宫破裂）20例，比较两组孕妇妊娠早期LUS瘢痕最薄处的肌层厚度，比较妊娠晚期定性观察LUS肌层连续性与测量LUS肌层厚度以评价子宫破裂的敏感度及特异度。 结果： 134例子宫未破裂组孕妇中，自然分娩者6例、行剖宫产术者128例；子宫破裂组20例，均为行剖宫产术分娩。子宫未破裂组及破裂组孕妇妊娠晚期LUS的肌层厚度分别为（1.6±0.5）、（1.1±0.7）mm，两组比较，差异有统计学意义（P=0.004）。两组孕妇的年龄、身高、体重、距前次剖宫产术的间隔时间、妊娠早期LUS瘢痕的肌层厚度分别比较，差异均无统计学意义（P均>0.05）。与测量LUS肌层厚度相比，定性观察LUS肌层连续性在妊娠晚期提示子宫破裂的特异度（99%）、阳性预测值（92%）、阴性预测值（94%）均较高，敏感度（60%）略低。 结论： 妊娠早期剖宫产术瘢痕的厚度与剖宫产术后再次妊娠孕妇发生子宫破裂的相关性不大，无必要因剖宫产术后子宫瘢痕薄或存在较小CSD而终止妊娠，但应在妊娠期密切超声监测LUS情况。妊娠晚期定性观察LUS肌层连续性较常规测量厚度，对于提示发生子宫破裂更有意义。.
Keywords: Cesarean section; Cicatrix; Pregnancy trimester, first; Uterine rupture.