Second-trimester sonographic comparison of the lower uterine segment in pregnant women with and without a previous cesarean delivery.

OBJECTIVE: To compare measurements of the lower uterine segment during a second-trimester sonographic examination in women with and without a previous cesarean delivery. METHODS: Women undergoing second-trimester sonographic examination, 24 with a history of cesarean delivery and 30 control subjects with no history of cesarean delivery, were recruited for transvaginal sonographic evaluation of the lower uterine segment with a high-frequency probe. The uterine niche or previous cesarean scar site was defined as a small triangular anechoic defect in the anterior wall of the uterus. The uterine wall thickness was measured successively at the level where the bladder dome meets the lower uterine segment. Measurements were obtained with cursors at the interface of the urine-bladder and the amniotic fluid-decidua. The study was approved by the Institutional Review Board, and P < .05 was considered significant. RESULTS: The uterine niche was identified in 14 (58%) of 24 women with a previous cesarean delivery. The lower uterine segment was significantly thinner in women with a previous cesarean delivery compared with control subjects (mean +/- SD, 4.7 +/- 1.1 versus 6.6 +/- 2.0 mm; P < .001). In the previous cesarean group, the mean lower uterine segment thickness was similar in the 5 women with 2 cesarean deliveries when compared with those with 1 cesarean delivery (4.6 +/- 1.0 versus 4.7 +/- 1.4 mm; P = .91). In a linear regression model, the only variable retaining significance in the prediction of uterine wall thickness was previous cesarean delivery (P= .002). Maternal age, parity, number of previous cesarean deliveries, and gestational age did not attain significance in the model. CONCLUSIONS: The lower uterine segment during a second-trimester sonographic examination is significantly thinner in women with a previous cesarean delivery. Identification of the scar niche is possible in most of these women.     

First-trimester diagnosis and management of pregnancies implanted into the lower uterine segment Cesarean section scar.

OBJECTIVE: To describe first-trimester ultrasound diagnosis and management of pregnancies implanted into uterine Cesarean section scars. METHODS: All women referred for an ultrasound scan because of suspected early pregnancy complications were screened for pregnancies implanted into a previous Cesarean section scar. The management of Cesarean section scar pregnancies included transvaginal surgical evacuation, medical treatment with local injection of 25 mg methotrexate into the exocelomic cavity and expectant management. RESULTS: Eighteen Cesarean section scar pregnancies were diagnosed in a 4-year period. The prevalence in the local population was 1 : 1800 pregnancies. Surgical treatment was used in eight women and it was successful in all cases. The respective success rates of medical treatment and expectant management were 5/7 (71%) and 1/3 (33%). Five women (28%) required blood transfusion and one woman (6%) had a hysterectomy. CONCLUSIONS: Cesarean section scar pregnancies are more common than previously thought. When the diagnosis is made in the first trimester the prognosis is good and the risk of hysterectomy is relatively low.     

超声自动全容积扫查系统测量晚孕期瘢痕子宫前壁下段肌层厚度

目的 通过与传统二维高频超声及术中超声的对比,探讨超声自动全容积扫查系统(AVSS)预测瘢痕子宫前壁下段肌层厚度的价值。方法 对24名预行剖宫产的晚孕期瘢痕子宫孕妇,于手术前一天分别进行AVSS成像及二维高频超声(2DHF)扫查,记录图像并分别测量子宫前壁下段肌层厚度;次日,将术中高频超声直接放置于子宫瘢痕区域测量肌壁厚度,并与术前AVSS及2DHF结果对比分析。结果 AVSS系统可以显示孕妇腹壁下段的皮肤、皮下脂肪及腹直肌结构;同时可以清晰显示子宫浆膜层、肌层与黏膜层的结构关系。AVSS的测值与术中超声测值呈正相关(r=0.76, P<0.01),与术中超声的测量差值集中在≤0.5 mm范围内。结论 AVSS测量晚孕期瘢痕子宫前壁下段肌层厚度重复性好,其测值更接近术中实际厚度。     

Sonographic evaluation of the wall thickness of the lower uterine segment in patients with previous cesarean section

In pregnant women with a history of cesarean section, wall thickness of the lower uterine segment may help determine the risk and safety of vaginal delivery. Determination of wall thickness may help identify the potential risk of uterine rupture in pregnant women who do not wish to have another cesarean section or who are not eligible for surgery due to other systemic disorders. In this study, 50 pregnant women with previous cesarean sections were evaluated with ultrasound preoperatively, and measurements of the lower uterine segment wall thickness were compared with intraoperative assessment of uterine thinning. These findings correlated highly with each other (sensitivity: 100%; specificity: 82% positive predictive value: 87%; negative predictive value: 100%), suggesting the reliability and safety of ultrasound in evaluating uterine wall thickness. © 1996 John Wiley & Sons, Inc.     

Sonographic evaluation of the lower uterine segment in patients with previous cesarean delivery.

OBJECTIVE: To evaluate the appearance of the lower uterine segment (LUS) in pregnant women with previous cesarean delivery and to compare the LUS thickness with that in women with unscarred uteri. METHODS: In a prospective study, sonographic examination was performed on 53 pregnant women with previous cesarean delivery (cesarean group), 40 nulliparas (nullip-control), and 40 women who had 1 or more childbirths with unscarred uteri (multip-control) between 36 and 38 weeks' gestation to assess the appearance and compare the thickness of the LUS. In the cesarean group, the sonographic findings were correlated with the delivery outcome and the intraoperative LUS appearance. RESULTS: In the cesarean group, 44 patients (83.0%) had a normal-appearing LUS indistinguishable from that of control groups; 2 patients (3.8%) had an LUS defect suggestive of dehiscence; and 7 patients (13.2%) had thickened areas of increased echogenicity with or without myometrial thinning. Although the cesarean group had a thinner LUS (1.9 +/- 1.4 mm) when compared with both the nullip-control group (2.3 +/- 1.1 mm; P > .05) and the multip-control group (3.4 +/- 2.2 mm; P < .001), only the latter difference achieved statistical significance. One of the 2 patients who had a sonographically suspected LUS defect had confirmed uterine dehiscence during surgery. An intraoperatively diagnosed paper-thin LUS, when compared with an LUS of normal thickness, had significantly smaller sonographic LUS measurements (1.1 +/- 0.6 versus 2.0 +/- 0.8 mm, respectively; P = .004). CONCLUSIONS: Prior cesarean delivery is associated with a sonographically thinner LUS when compared with those with prior vaginal delivery. Prenatal sonographic examination is potentially capable of diagnosing a uterine defect and determining the degree of LUS thinning in patients with previous cesarean delivery.     

Ultrasonography of the lower uterine segment after multiple caesarean sections

Transvaginal ultrasonic monitoring of the lower uterine segment was performed in 15 pregnancies in which the mother had previously had three or more caesarean sections. The typical findings were thinning of the myometrium, asymmetric isthmal structures and ventral ballooning of the isthmus. An image of the other of the two isthmal fenestrations was obtained by ultrasound. The antepartum ultrasonic findings and those found at operation correlated well. Maternal antepartum symptoms, on the other hand, poorly reflected the physical state on the scarred uterine isthmus.     

子宫下段剖宫产切口部位早期妊娠的临床研究

目的探讨子宫下段剖宫产切口部位早期妊娠的临床表现、超声特征、诊断、治疗及其预后。方法收集1996年至2006年间收治的病例,对17例子宫下段剖宫产切口部位早期妊娠的临床诊治经过进行回顾性分析。结果17例子宫下段剖宫产切口部位早期妊娠患者均有停经后的无痛性阴道不规则少量出血及血β-HCG升高的临床表现。剖宫产至发病时间最短0·5年,最长为12年,平均(6·9±3·5)年。多普勒超声显示子宫下段剖宫产切口部位明显膨大,并可见孕囊或混合性团块附着于该处,孕囊与膀胱壁间的子宫肌层菲薄。其中12例经结晶天花粉宫颈注射、口服米非司酮或肌内注射氨甲喋呤等治疗,血β-HCG降至正常。2例经药物治疗后在超声监视下行清宫术,术后血β-HCG降至正常。2例因阴道大出血而行全子宫切除。另1例因误诊为滋养细胞肿瘤行全子宫切除。结论子宫下段瘢痕子宫妊娠应常规行超声检查,对于子宫下段剖宫产切口部位早期妊娠的早期诊断和有效的药物保守治疗能减少子宫破裂的发生。     

Pre-induction sonographic measurement of cervical length in prolonged pregnancy: the effect of parity in the prediction of the need for Cesarean section.

OBJECTIVE: To examine the effect of parity on the relationship between pre-induction cervical length and the risk of Cesarean section in women undergoing induction of labor for prolonged pregnancy. METHODS: In 382 singleton pregnancies, induction of labor was carried out at 41 + 3 to 42 + 1 weeks of gestation. The cervical length was measured by transvaginal sonography before induction. In 71 of these cases a Cesarean section was required for either fetal distress or failure to progress and 311 women delivered vaginally. The effect of parity and pre-induction cervical length on the risk of Cesarean section was examined. RESULTS: In nulliparous women the incidence of Cesarean section was significantly higher than in multiparous women (28.1% vs. 8.9%). In both nulliparae and multiparae there was a significant association between pre-induction cervical length and the rate of Cesarean section. Logistic regression analysis demonstrated that cervical length and parity provided significant independent prediction of all Cesarean sections and Cesarean sections for failure to progress. The odds of Cesarean section increased by about 10% with each increase of 1 mm in cervical length, over the mean cervical length of 20 mm for nulliparae and 18 mm for multiparae, and the odds was about 75% lower in multiparae, compared to nulliparae with the same cervical length. Receiver-operating characteristics curves (ROC) demonstrated that cervical length was better than the Bishop score in the prediction of all Cesarean sections (area under ROC = 0.72 vs. 0.68) and Cesarean sections for failure to progress (area under ROC = 0.76 vs. 0.69). CONCLUSION: In women undergoing induction of labor for prolonged pregnancy, cervical length and parity provide significant independent prediction of the likelihood of Cesarean section.     

剖宫产后2年内宫内足月妊娠时子宫前壁下段的超声表现

目的探讨剖宫产后2年内宫内足月妊娠时子宫前壁下段的超声表现。方法回顾性分析102例剖宫产术后2年内再次妊娠女性孕晚期的子宫前壁下段超声表现,并分析再次剖宫产患者术中切开瘢痕情况,探讨两者的相关性。结果超声各观察指标：子宫前壁下段厚度≥3 mm、子宫前壁下段各层结构分界清晰、子宫前壁下段肌层回声连续、肌层最薄处的厚度≥2 mm及子宫前壁下段出现点状血流评价瘢痕愈合良好灵敏度分别为89.1%、83.6%、75.6%、67.5%和94.5%,其中子宫前壁下段肌层最薄处厚度≥2 mm的特异度最高,达80.0%。结论超声能较准确地反映瘢痕情况,可为剖宫产术后2年内再次宫内足月妊娠女性分娩方式选择提供重要依据。     

Assessment of the intraobserver variability in the measurement of fetal cardiothoracic ratio using ellipse and diameter methods.

OBJECTIVE: To assess the variability of fetal heart and thoracic area and circumference measurements using the ellipse and diameter methods at different gestational ages. DESIGN: This was a prospective cross-sectional study of 200 singleton pregnancies, with no apparent fetal abnormalities. The gestational age ranged between 19 and 42 weeks. At each examination, two transverse frames of the fetal chest at the level of the four-chamber view during diastole were obtained. For each frame, the area and the circumference of the heart and thorax were obtained by the ellipse and diameter methods. In the diameter method, cardiac and thoracic areas and circumferences were derived from the measured anteroposterior and transverse diameters. All measurements were made by the same observer. RESULTS: For the same method, intraobserver variability was good. Coefficient of variation for all measurements varied between 3-11%. The ellipse method tended to give larger measurements than did the diameter method, the absolute difference increasing with fetal age. The mean ellipse/diameter ratio was 1.10, 1.04, 1.05 and 1.02 for heart area, thorax area, heart circumference and thorax circumference, respectively. In most cases, intraobserver variability of the thorax measurements was independent of gestational age. In contrast, there was a greater variability of heart measurements with increasing gestational age. CONCLUSIONS: Both the ellipse and diameter methods of measuring cardiothoracic ratio are clinically useful and fairly reproducible at certain gestations, but are not interchangeable as the ellipse method overestimates measurements compared to the diameter method. The less reproducible measurement of heart size in later gestation should be taken into account when assessing cardiothoracic ratios.     

Sonographic imaging of cervical scars after Cesarean section.

OBJECTIVE: To investigate whether uterine contractions at the time of a Cesarean section have an impact on future presence and location of a cervical Cesarean scar. METHODS: A targeted transvaginal ultrasound examination of the fetus, uterus and cervix was done in 2973 consecutive women at 14-16 weeks' gestation. The sonographer was blinded to the women's previous obstetric histories. The presence and location of a sonographic cervical hypoechogenic line, which probably represented a Cesarean scar, was recorded. RESULTS: There were 180 women with a previous Cesarean section performed before the start of uterine contractions and 173 with a Cesarean section performed during contractions in labor. The cervical hypoechogenic line was more common in sections performed during contractions (75.7% vs. 52.7%; P < 0.001) and was more distally located from the internal os (17.9 +/- 9.4 vs. 14.6 +/- 9.1 mm; P = 0.01). A hypoechogenic line was observed in 21/2620 women without a previous Cesarean section, representing a false-positive rate of 0.8%. CONCLUSION: Cesarean sections, especially those done during uterine contractions, are actually performed through cervical tissue. This finding is in agreement with the physiological process of cervical effacement during contractions.