[Correlation between uterine scar condition and uterine rupture for pregnancy women after previous cesarean section]

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.