Comparison of transabdominal versus transvaginal ultrasound to measure thickness of the lower uterine segment at term

Accuracy of sonographic lower segment thickness and prediction of vaginal birth after caesarean in a resourced-limited setting; Prospective study

OBJECTIVES

To assess the accuracy of ultrasound measurement of the lower uterine segment (LUS) thickness against findings at laparotomy, and to investigate its correlation with the success rate of vaginal birth after one previous caesarean delivery (CD) in a resource-limited setting.

DESIGN

Prospective study.

SETTING

Obstetrics and Gynaecology department in a tertiary hospital in Ghana.

POPULATION

Women with one previous CD undergoing either a trial of labour (TOLAC) or elective CD.

METHODS

Myometrial lower uterine segment thickness (mLUS) and full lower uterine segment thickness (fLUS) were measured with transvaginal ultrasound (TVUS). The women were managed according to local protocols with the clinicians blinded to the ultrasound measurements. The LUS was measured intraoperatively for comparison with ultrasound measurements.

MAIN OUTCOME MEASURES

Lower uterine segment findings at laparotomy, successful vaginal birth.

RESULTS

A total of 311 pregnant women with one previous CD were enrolled; 147 women underwent elective CD and 164 women underwent a TOLAC. Of the women that underwent TOLAC, 96 (58.5%) women had a successful vaginal birth. The mLUS was comparable to the intraoperative measurement in the elective CD group with LUS thickness <5 mm (bias of 0.01, 95% CI -0.10 to 0.12 mm) whereas fLUS overestimated LUS <5 mm (bias of 0.93, 95% CI 0.80-1.06 mm). Successful vaginal birth rate correlated with increasing mLUS values (odds ratio 1.30, 95% CI 1.03-1.64). Twelve cases of uterine defect were recorded. LUS measurement ≤2.0 mm was associated with an increased risk of uterine defects with a sensitivity of 91.7% (95% CI 61.5-99.8%) and specificity of 81.8% (95% CI 75.8-86.8%).

CONCLUSION

Accurate TVUS measurement of the LUS is technically feasible in a resource-limited setting. This approach could help in making safer decisions on mode of birth in limited-resource settings.

Transabdominal versus transvaginal ultrasound to assess the thickness of lower uterine segment at term in women with previous cesarean section

OBJECTIVE

This study aims to compare transvaginal (TVS) and transabdominal (TAS) ultrasonography precision in to evaluate the lower uterine (LUS) thickness in women with a previous Cesarean section at the term pregnancy; to be an effective method for assessment of previous cesarean scar strength.

MATERIAL AND METHODS

An observational cross-sectional study was conducted at kasr el-ainy Hospital in Egypt. From May to November 2020, we admitted 130 pregnant women at term with a previous cesarean section for an elective cesarean delivery. Lower uterine segment thickness was obtained using both transvaginal ultrasound and transabdominal ultrasound before the cesarean. The exact thickness of the lower uterine segment was recorded using a sterile metal ruler before the neonate had been delivered.

RESULTS

The mean thickness of the lower uterine segment obtained by transabdominal ultrasound was 5.2 ± 1.6 mm and 4.8 ± 1.33 mm by transvaginal ultrasound, then compared each of them to the mean actual thickness, which was 4.5 ± 1.22 mm. The lower uterine segment thickness with transabdominal ultrasound showed a good correlation (r = 0.722) with the actual thickness, the correlation with transvaginal ultrasound was better (r = 0.944). A cut-off value transvaginal ultrasound of 3.65 mm with 90.8% sensitivity and 65.6% specificity.

CONCLUSION

Transvaginal ultrasound is more accurate in assessing the thickness of the lower uterine segment than transabdominal ultrasound. A total lower uterine segment thickness of <3.65 is considered a thin scar, and <2.85 mm is associated with a higher risk of uterine dehiscence. The trial was registered in ClinicalTrials.gov registry with clinical trial. https://clinicaltrials.gov/ct2/show/NCT04687891.

Diagnosing early scar pregnancy in the lower uterine segment after cesarean section by intracavitary ultrasound

BACKGROUND

Early scar pregnancy (CSP) in the lower uterine segment after cesarean section is a type of ectopic pregnancy that can cause major complications if left untreated. Transabdominal ultrasound is a common procedure but is influenced by external factors. Thus, intracavitary ultrasound may have better diagnostic efficiency for CSP.

AIM

To assess the value of intracavitary ultrasound for diagnosing CSP in the lower uterine segment after cesarean section.

METHODS

Patients diagnosed with CSP in our hospital from October 2019 to April 2021 were recruited. Transabdominal and intracavitary ultrasound examinations were performed to compare the diagnostic differences for CSP and its types.

RESULTS

Sixty-three patients were diagnosed during the study period. The diagnostic accuracy for CSP was higher in intracavitary ultrasound (96.83%) than in transabdominal ultrasound (84.13%) (P < 0.05). The missed diagnosis and misdiagnosis rates did not differ among the ultrasound types (intra: 0.00% and 3.17%; trans: 4.76% and 11.11%, respectively; P > 0.05). For the diagnostic rates for the CSP types, the rates for gestational sac (100.00% vs 90.48%), heterogeneous mass (93.75% vs 75.00%), and part of the uterine cavity (80.00% vs 60.00%) were higher in intracavitary ultrasound than in transabdominal ultrasound, but the difference was not statistically significant (P > 0.05). For gestational sac CSP patients, intracavitary ultrasound showed that the gestational sac was located in the lower uterine segment scar with abundant peripheral blood flow; the distance between the gestational sac and the serosal layer was 2.42 ± 0.50 cm. Intracavitary ultrasound for heterogeneous mass CSP patients indicated that the mass mainly occurred in the lower anterior uterine wall, protruding into the bladder, and was surrounded by abundant internal and peripheral blood flow; the distance between the mass and serosal layer was 1.79 ± 0.30 cm. For CSP type partly located in the uterine cavity, the gestational sac was partly located in the lower uterine cavity and partly in the scar with abundant internal and peripheral blood flow; the distance between the gestational sac and the serosal layer was 2.29 ± 0.28 cm.

CONCLUSION

Intracavitary ultrasound had a higher diagnostic accuracy and application value for diagnosing CSP than transabdominal ultrasound, with reduced risk of missed diagnoses and misdiagnosis, thereby preventing delayed treatment.

Evaluation of uterine scar healing by transvaginal ultrasound in 607 nonpregnant women with a history of cesarean section

BACKGROUND

Caesarean scar defect (CSD) seriously affects female reproductive health. In this study, we aim to evaluate uterine scar healing by transvaginal ultrasound (TVS) in nonpregnant women with cesarean section (CS) history and to build a predictive model for cesarean scar defects is very necessary.

METHODS

A total of 607 nonpregnant women with previous CS who have transvaginal ultrasound measurements of the thickness of the lower uterine segment. The related clinical data were recorded and analyzed.

RESULTS

All patients were divided into two groups according to their clinical symptoms: Group A (N = 405) who had no cesarean scar symptoms, and Group B (N = 141) who had cesarean scar symptoms. The difference in frequency of CS, uterine position, detection rate of CSD and the residual muscular layer (TRM) of the CSD were statistically significant between groups; the TRM measurements of the two groups were (mm) 5.39 ± 3.34 versus 3.22 ± 2.33, P < 0.05. All patients were divided into two groups according to whether they had CSDs: Group C (N = 337) who had no CSDs, Group D (N = 209) who had CSDs on ultrasound examination. The differences in frequency of CS, uterine position, TRM between groups were statistically significant (P < 0.05). In the model predicting CSDs by TRM with TVS, the area under the ROC curve was 0.771, the cut-off value was 4.15 mm. The sensitivity and specificity were 87.8% and 71.3%, respectively.

CONCLUSIONS

Patients with no clinical symptoms had a mean TRM on transvaginal ultrasonography of 5.39 ± 3.34 mm, which could be used as a good reference to predict the recovery of patients with CSDs after repair surgery.

The B-mode sonographic evaluation of the post-caesarean uterine wall and its methodology: A study protocol

AIM

The aim of this study is to utilize the niche measurement guidelines outlined by Jordans et al. in order to establish normal values and accurate description of caesarean section scars in a normal population. After defining the normal distribution, abnormal pregestational scar characteristics will be identified for predicting adverse pregnancy outcomes.

METHODS

This is a prospective observational multicenter clinical study where women with a history of only one caesarean section and yet open family planning are enrolled. The uterine length, cervical length, niche length, niche depth, niche width, residual myometrial thickness, endometrial thickness, scar to internal os distance, anterior myometrial thickness superior and inferior to the scar and the posterior myometrial thickness opposite the scar, superior and inferior to it are measured in a pregestational uterus. The lower uterine segment is measured over a length of 3 cm during subsequent pregnancy and followed up until delivery.

RESULTS

Data from 500 patients will yield normal distribution curves for all predefined measurements. Establishing a correlation between deviations from the normal measures and adverse events would be instrumental for counseling women regarding subsequent pregnancy and mode of delivery.

CONCLUSION

This study will demonstrate the changes of the post-caesarean scar from a non-pregnant uterus until delivery and can confirm the importance of the scar characteristics in predicting pregnancy outcome.

Comparison of scar thickness measurements using trans-vaginal sonography and MRI in cases of pregnancy with previous caesarean section. Do they correlate with actual scar thickness?

The aim of this study was to evaluate scar thickness in cases of pregnancy with previous caesarean section, by trans-vaginal sonography (TVS) and magnetic resonance imaging (MRI), and to correlate precision of radiologically-measured scar thickness with actual measurement of scar thickness. A total of 35 pregnant patients with previous caesarean section planned for elective caesarean section, were evaluated prospectively. Their scar thickness was measured by TVS and MRI on the day of elective repeat caesarean section. These measurements were correlated with each other and with scar thickness measured during elective repeat caesarean section by using a caliper. The correlation coefficients between scar thickness measured by TVS and MRI with peroperative evaluation with a caliper, were +0.72 and +0.59, respectively. The study concluded that as MRI is a costlier modality and TVS has better correlation coefficient with actual scar thickness, TVS can be considered to be the better modality for antenatal scar thickness measurement.

Effective anatomical and functional status of the lower uterine segment at term: estimating the risk of uterine dehiscence by ultrasound

OBJECTIVE

To define the role of lower uterine segment (LUS) evaluation at term.

DESIGN

Observational case-control study.

SETTING

University hospital.

PATIENT(S)

Ninety-four patients were divided into two groups. Group A consisted of 45 multiparous single fetus pregnant women with up to two previous cesarean sections (CS). Group B consisted of 49 multiparous pregnant women with up to three vaginal deliveries and no uterine scars.

INTERVENTION(S)

Total LUS and myometrial thickness were measured by sonogram in all patients before undergoing a CS.

MAIN OUTCOME MEASURE(S)

The primary outcome is a correlation between echographic measurements and features of the LUS at the time of CS. The secondary outcome is a definition of a correlation between the number of previous CS, interdelivery interval time, and features of the LUS (grades I-IV).

RESULT(S)

Sonographic measurements revealed significant differences in LUS size and myometrial thickness between the two groups. Grades III and IV of LUS were only observed in group A. An interdelivery interval <18 months, LUS thickness ≤ 3.0 mm, and myometrial thickness < 1.5 mm were statistically significant predictors of LUS grades III and IV. Number of previous CS showed no correlation with surgical LUS status.

CONCLUSION(S)

Sonographic evaluation of the LUS may be a noninvasive, reproducible, and safe technique for defining the risk of uterine dehiscence, with a sensitivity of 100% and specificity of 85% (positive predictive value, 45%; negative predictive value, 100%).

Pitfall in ultrasound evaluation of uterine scar from prior preterm cesarean section

We report two cases of women with a previous cesarean performed before active labor at 29 weeks of gestation who underwent sonographic measurement of the lower uterine segment (LUS) at 36 weeks' gestation in their subsequent pregnancy. In both cases, uterine scar defect was detected on the upper part of the LUS, at ∼9 to 11 cm from the cervical os, and was only visualized by the transabdominal approach. We suggest that early gestational age and the absence of labor at previous cesarean can lead to a higher uterine scar location on the LUS and, therefore, increase the risk of uterine rupture in subsequent pregnancy. The heterogeneity of uterine scar location could explain discrepancies observed in studies using the transabdominal versus the transvaginal approach or both regarding the predictive value of LUS measurements for uterine rupture.