Cheung Vincent Y T
Department of Obstetrics and Gynaecology, North York General Hospital, Toronto, ON.
J Obstet Gynaecol Can. 2005 Jul;27(7):674-81. doi: 10.1016/s1701-2163(16)30545-x.
To evaluate the accuracy of prenatal sonography in determining the lower uterine segment (LUS) thickness in women with previous Caesarean section and to assess the usefulness of measuring LUS thickness in predicting the risk of uterine rupture during a trial of vaginal birth.
Sonographic examination was performed in 102 pregnant women with one or more previous Caesarean sections at between 36 and 38 weeks' gestation to assess the LUS thickness, which was defined as the shortest distance between the urinary bladder wall-myometrium interface and the myometrium/chorioamniotic membrane-amniotic fluid interface. Of the 102 women examined, 91 (89.2%) had transabdominal sonography only, and 11 (10.8%) had both transabdominal and transvaginal examinations. The sonographic measurements were correlated with the delivery outcome and the intraoperative LUS appearance.
The mean sonographic LUS thickness was 1.8 mm, standard deviation (SD) 1.1 mm. An intraoperatively diagnosed paper-thin or dehisced LUS, when compared with an LUS of normal thickness, had a significantly smaller sonographic LUS measurement (0.9 mm, SD 0.5 mm, vs. 2.0 mm, SD 0.8 mm, respectively; P < 0.0001). Two women had uterine dehiscence, both of whom had prenatal LUS thickness of < 1 mm. Thirty-two women (31.4%) had a successful vaginal delivery, with a mean LUS thickness of 1.9 mm, SD 1.5 mm; none had clinical uterine rupture. A sonographic LUS thickness of 1.5 mm had a sensitivity of 88.9%, a specificity of 59.5%, a positive predictive value of 32.0%, and a negative predictive value of 96.2% in predicting a paper-thin or dehisced LUS.
Sonography permits accurate assessment of the LUS thickness in women with previous Caesarean section and therefore can potentially be used to predict the risk of uterine rupture during trial of vaginal birth.
评估产前超声检查在确定有剖宫产史女性子宫下段（LUS）厚度方面的准确性，并评估测量LUS厚度在预测阴道试产期间子宫破裂风险中的作用。
对102例有一次或多次剖宫产史的孕妇在妊娠36至38周时进行超声检查，以评估LUS厚度，LUS厚度定义为膀胱壁 - 肌层界面与肌层/绒毛羊膜 - 羊水界面之间的最短距离。在接受检查的102例女性中，91例（89.2%）仅接受了经腹超声检查，11例（10.8%）同时接受了经腹和经阴道检查。超声测量结果与分娩结局及术中LUS表现相关。
超声测量的LUS平均厚度为1.8mm，标准差（SD）为1.1mm。与正常厚度的LUS相比，术中诊断为纸样薄或裂开的LUS，其超声测量值明显更小（分别为0.9mm，SD 0.5mm，与2.0mm，SD 0.8mm；P < 0.0001）。两名女性发生子宫裂开，她们产前LUS厚度均<1mm。32名女性（31.4%）成功进行了阴道分娩，LUS平均厚度为1.9mm，SD为1.5mm；无一例发生临床子宫破裂。超声LUS厚度为1.5mm在预测纸样薄或裂开的LUS时，敏感性为88.9%，特异性为59.5%，阳性预测值为32.0%，阴性预测值为96.2%。
超声检查能够准确评估有剖宫产史女性的LUS厚度，因此有可能用于预测阴道试产期间子宫破裂的风险。
