Ultrasonographic evaluation of lower uterine segment to predict the integrity and quality of cesarean scar during pregnancy: a prospective study

[Usefulness of ultrasound measurement of the lower uterine segment before delivery of women with a prior cesarean: Literature review]

Identifying women with a history of cesarean delivery and at real risk for uterine rupture is an important aim in obstetric care. It is with this objective that different authors have evaluated the interest of ultrasound for predicting the risk of a cesarean scar defect by measuring the thickness of the lower uterine segment. The literature is sparse and subject to numerous biases because they are mainly prospective cohort studies with small numbers. However, the results are concordant: Ultrasound measurements of lower uterine segment thickness are strongly correlated with the operative findings observed during cesarean delivery. Moreover, the thinner the lower uterine segment on ultrasound, the higher the likelihood of a uterine defect. Two randomized trials have recently been published. The PRISMA cluster randomized controlled trial evaluated a multifaceted intervention including an ultrasound estimation of the risk of uterine rupture by ultrasound measurement of the lower uterine segment thickness and aimed at helping women in their choice of mode of delivery after a previous cesarean delivery. This multifaceted intervention resulted in a significant reduction in the rates of major perinatal and maternal morbidity, without any increase in the rate of cesarean delivery or uterine rupture. However, due to its design, it is impossible to specifically specify the benefit of lower uterine segment measurement in reducing major maternal and perinatal morbidity since the trial combined several interventions. The LUSTrial randomized controlled trial evaluated the impact on maternal-fetal morbidity and mortality of proposing a mode of delivery based on ultrasound measurement of the lower uterine segment thickness compared to usual care among women with a history of cesarean delivery. Ultrasound measurement of lower uterine segment thickness was not associated with a statistically significant reduction in maternal-fetal morbidity and mortality compared to usual care. In this literature review, we will mainly detail and analyze the results of this trial.

Perinatal morbidity among women with a previous caesarean delivery (PRISMA trial): a cluster-randomised trial

BACKGROUND

Women with a previous caesarean delivery face a difficult choice in their next pregnancy: planning another caesarean or attempting vaginal delivery, both of which are associated with potential maternal and perinatal complications. This trial aimed to assess whether a multifaceted intervention, which promoted person-centred decision making and best practices, would reduce the risk of major perinatal morbidity among women with one previous caesarean delivery.

METHODS

We conducted an open, multicentre, cluster-randomised, controlled trial of a multifaceted 2-year intervention in 40 hospitals in Quebec among women with one previous caesarean delivery, in which hospitals were the units of randomisation and women the units of analysis. Randomisation was stratified according to level of care, using blocked randomisation. Hospitals were randomly assigned (1:1) to the intervention group (implementation of best practices and provision of tools that aimed to support decision making about mode of delivery, including an estimation of the probability of vaginal delivery and an ultrasound estimation of the risk of uterine rupture), or the control group (no intervention). The primary outcome was a composite risk of major perinatal morbidity. This trial was registered with ISRCTN, ISRCTN15346559.

FINDINGS

21 281 eligible women delivered during the study period, from April 1, 2016 to Dec 13, 2019 (10 514 in the intervention group and 10 767 in the control group). None were lost to follow-up. There was a significant reduction in the rate of major perinatal morbidity from the baseline period to the intervention period in the intervention group as compared with the control group (adjusted odds ratio [OR] for incremental change over time, 0·72 [95% CI 0·52-0·99]; p=0·042; adjusted risk difference -1·2% [95% CI -2·0 to -0·1]). Major maternal morbidity was significantly reduced in the intervention group as compared with the control group (adjusted OR 0·54 [95% CI 0·33-0·89]; p=0·016). Minor perinatal and maternal morbidity, caesarean delivery, and uterine rupture rates did not differ significantly between groups.

INTERPRETATION

A multifaceted intervention supporting women in their choice of mode of delivery and promoting best practices resulted in a significant reduction in rates of major perinatal and maternal morbidity, without an increase in the rate of caesarean or uterine rupture.

FUNDING

Canadian Institutes of Health Research (CIHR, MOP-142448).

Comparison of Clinical and Radiological Findings for the Prediction of Scar Integrity in Women With Previous Lower Segment Cesarean Sections

INTRODUCTION

We aimed to compare the clinical and radiological findings to predict scar integrity in term antenatal mothers with a previous lower segment cesarean section (LSCS).

METHODOLOGY

This prospective study was conducted in the obstetrics and gynecology department of LN Medical College, Bhopal, India, from August 2020 to August 2021. We included all pregnant women with term gestation (37+0 to 42+0 weeks) who were admitted either for elective repeat LSCS or for emergency LSCS and had a history of a previous LSCS. A detailed history and clinical examinations were performed. We noted the presence of scar tenderness and conducted transabdominal ultrasound (USG) to assess the integrity of the uterine scar in all women. During surgery, the surgeon identified the lower uterine segment scar and graded it as normal, thinned-out, dehiscent, or ruptured. We calculated sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) for both clinical findings (scar tenderness) and ultrasound findings as predictors of scar integrity.

RESULTS

A total of 60 pregnant women were included in the study. During a repeat cesarean section, we found a thinned-out scar in 26 women out of 60 (43.3%). Out of 60 women, 13 had scar tenderness, and among these 13 women, 12 had thinned-out scars intraoperatively. Forty-seven women had no scar tenderness; 14 had thinned-out scars intraoperatively. The sensitivity of scar tenderness as a predictor of a thinned-out scar was 46.2%, specificity was 97.1%, PPV was 92.3%, and NPV was 70.2%. Whereas the sensitivity of ultrasound scar thickness as a predictor of a thinned-out scar was only 19.2%, with a specificity of 94.1%, a PPV of 71.4%, and an NPV of 60.4%. Thus, we documented a significant correlation between intraoperative and clinical findings (κ = 0.46; p<0.05), but no agreement could be found between ultrasound and intraoperative findings (p>0.05).

CONCLUSIONS

Clinically evident scar tenderness continues to be a useful parameter to predict intraoperative scar status.

Predicting Uterine Rupture Risk Using Lower Uterine Segment Measurement During Pregnancy With Cesarean History: How Reliable Is It? A Review

Importance

Uterine rupture during labor is a calamitous event that can result in maternal/neonatal morbidity/mortality. Lower uterine segment (LUS) thickness measurement is a proposed method to determine the risk factor of uterine rupture in women undergoing trial of labor after cesarean. Does this measurement predict uterine rupture risk?

Objectives

This review examines current evidence to determine if a thin LUS ultrasound diagnosis during pregnancy with prior cesarean delivery(s) can reliably predict uterine rupture risk while attempting vaginal birth after cesarean (VBAC).

Evidence Acquisition

Electronic databases (PubMed and CINAHL) were searched with one limitation of abstracts in English. Search terms used were "lower uterine segment" AND "risk(s)" AND "rupture" OR "dehiscence.

Results

After reviewing 164 identified articles, 15 were used in this review. Of the studies including LUS thickness measurement, notable differences were found: gestational age at time of measurement, full thickness measurement versus myometrial thickness, number of sonographers involved, ultrasound technique (transabdominal vs transvaginal), and blinding. Other factors influencing LUS thickness include fetal weight, amniotic fluid volume, and gestational age. The most recent systematic review and meta-analysis suggests that an LUS > 3.65 mm should be safe for a VBAC, 2-3.65 mm is probably safe, and <2 mm identifies a patient at higher risk for uterine rupture/dehiscence.

Conclusions

Study heterogeneity, absence of an agreed upon thickness threshold, poor correlation between ultrasound and MRI measurements, or physical cesarean measurements currently make VBAC uterine rupture risk prediction uncertain.

Relevance

Our aim is to analyze existing literature to determine if evidence supports LUS measurement in women undergoing VBAC after cesarean to determine risk of uterine rupture.

New ultrasonographic risk assessment of uterine scar dehiscence in pregnancy after cesarean section

PURPOSE

We performed a new ultrasonographic risk assessment of uterine scar dehiscence, which is a potential risk factor for uterine rupture, in pregnancy after cesarean section. We attempted to shed light on the natural course of the change in the lower uterine segment by means of a longitudinal investigation through quantitative and qualitative evaluations.

METHODS

This retrospective single-center study involved 31 women with a normal singleton pregnancy delivered by elective cesarean section between 2020 and 2021, with all women showing a "niche" in the lower uterine segments. The lower uterine segments were assessed qualitatively and quantitatively using transvaginal ultrasonography at 16-21, 22-27, and 28-33 weeks of gestation, and subjects were divided into two groups: those with uterine dehiscence (12 women) and those without uterine dehiscence (19 women), depending on the gross findings of the lower uterine segments at cesarean section. Analyses were performed using Wilcoxon's rank-sum and Mann-Whitney U test with a significance level of P < 0.05.

RESULTS

The lower uterine segments changed from V-shaped to U-shaped to thin as gestation progressed and was more prominent in the uterine dehiscence group, occurring mostly at 22-27 weeks. At 22-27 weeks, the median myometrial thickness in the uterine dehiscence group was lower than in the group without uterine dehiscence (P = 0.0030). Thinning of the lower uterine segments had moved the cephalad at 22-27 and 28-33 weeks in cases with and without uterine dehiscence.

CONCLUSION

A model of morphological changes in the niche was constructed based on qualitative and quantitative assessments. The morphological changes and actual thinning of the lower uterine segments were prominent in the second trimester in women considered to have uterine scar dehiscence.

Subsequent Pregnancy Outcome in Women with Prior Complete Uterine Rupture: A Single Tertiary Care Centre Experience

Limited data is available to assess the burden of maternal morbidity, mortality, and perinatal outcome after subsequent pregnancy in women with prior uterine rupture. Therefore, this retrospective descriptive study was conducted to determine subsequent pregnancy outcomes in a larger series of women with prior complete uterine rupture. All pregnant women who had complete uterine rupture were managed according to the standard Institute protocol. The women who conceived following a uterine repair from July 2011 to June 2020 were recruited into the study. Outcome measures included severe maternal morbidities and perinatal outcomes. Fifty-three women with prior complete uterine rupture were conceived subsequently. Two women had an abortion in the first and second trimester, respectively. None of the women developed recurrence of uterine rupture. However, three women developed uterine dehiscence in a total of 16 women who went into spontaneous labour before elective cesarean delivery at 32, 36, and 37 weeks, respectively. None of the women had placenta previa, placenta accreta, bowel injury, bladder injury and none required a hysterectomy. However, 16.7% of women needed a blood transfusion. None of the women required mechanical ventilation, inotropic support, and intensive care unit stay. Seventeen babies required neonatal intensive care admission, and prematurity (90%) was the most common reason, followed by low APGAR scores. In conclusion, subsequent pregnancy outcomes in women with prior uterine rupture appear acceptable in institutionalized care. Timing of cesarean delivery may have to be weighed against the risk of prematurity-associated neonatal morbidity and mortality.

Evaluation of the usefulness of ultrasound measurement of the lower uterine segment before delivery of women with a prior cesarean delivery: a randomized trial

BACKGROUND

The main reason to avoid trial of labor after cesarean delivery is the possibility of uterine rupture. Identifying women at risk is thus an important aim, for it would enable women at low risk to proceed with a secure planned vaginal birth.

OBJECTIVE

To evaluate the impact of proposing mode of delivery based on the ultrasound measurement of the lower uterine segment thickness on a composite outcome of maternal-fetal mortality and morbidity, compared with usual management, among pregnant women with a previous cesarean delivery.

STUDY DESIGN

This multicenter, randomized, controlled, parallel-group, unmasked trial was conducted at 8 referral university hospitals with a neonatal intensive care unit and enrolled 2948 women at 36 weeks 0 days to 38 weeks 6 days of gestation with 1 previous low transverse cesarean delivery and no contraindication to trial of labor. Women in the study group had their lower uterine segment thickness measured by ultrasound. Those with measurements >3.5 mm, were encouraged to choose a planned vaginal delivery, and those with measurements ≤3.5 mm, were encouraged to choose a planned repeat cesarean delivery. This measurement was not taken in the control group; their mode of delivery was decided according to standard management. The primary outcome was a composite criterion comprising maternal mortality, uterine rupture, uterine dehiscence, hysterectomy, thromboembolic disease, transfusion, endometritis, perinatal death, or neonatal encephalopathy. Prespecified secondary outcomes were repeat cesarean deliveries, elective or after trial of labor.

RESULTS

The study group included 1472 women, and the control group included 1476 women. These groups were similar at baseline. The primary outcome occurred in 3.4% of the study group and 4.3% of the control group (relative risk, 0.78; 95% confidence interval, 0.54-1.13: risk difference, -1.0%; 95% confidence interval, -2.4 to 0.5). The uterine rupture rate in the study group was 0.4% and in the control group 0.9% (relative risk, 0.43; 95% confidence interval, 0.15-1.19). The planned cesarean delivery rate was 16.4% in the study group and 13.7% in the control group (relative risk, 1.21; 95% confidence interval, 1.00-1.47), whereas the rates of cesarean delivery during labor were 25.1% and 25.0% (relative risk, 1.01; 95% confidence interval, 0.89-1.14) in the study and control groups, respectively.

CONCLUSION

Ultrasound measurements of lower uterine segment thickness did not result in a statistically significant lower frequency of maternal and perinatal adverse outcomes than standard management. However, because this study was underpowered, further research should be encouraged.

Uterine dehiscence in pregnant with previous caesarean delivery

BACKGROUND

The main risk factor for uterine scar dehiscence is a previous caesarean section. Better characterisation of the ultrasonographic features of uterine scar dehiscence may improve preoperative diagnostic accuracy in pregnant women with a caesarean scar. This study aimed to evaluate the ultrasonographic features of uterine scar dehiscence in pregnant women and maternal and neonatal outcomes.

MATERIALS AND METHODS

This was a retrospective review of the records of 23 women with a previous caesarean section found to have uterine scar dehiscence during surgery. The integrity and thickness of the lower uterine segment were recorded, ultrasonographic features were evaluated, and maternal and infant outcomes were analysed.

RESULTS

Of the 23 cases of uterine scar dehiscence, six were detected by preoperative ultrasonography, while 17 were missed. The ultrasonographic features of the 23 cases of uterine dehiscence included anechoic areas protruding through the caesarean section scar with an intact serosal layer (4/23), disappearance of the muscular layer (2/23), and a thinner lower uterine segment (17/23). There were no cases of maternal or neonatal mortality. One woman chose to undergo pregnancy termination.

CONCLUSION

Preoperative detection of uterine scar dehiscence in women with previous caesarean delivery helps prevent maternal and neonatal morbidity and mortality. However, the maximum benefit can only be obtained by scanning at appropriate intervals during pregnancy and accurate recognition of the ultrasonographic features of uterine scar dehiscence.KEY MESSAGESPreoperative detection of uterine scar dehiscence in women with previous caesarean delivery helps prevent maternal and neonatal morbidity and mortality.Scanning at appropriate intervals during pregnancy and accurate recognition of the ultrasonographic features of uterine scar dehiscence could be beneficial.Even when uterine dehiscence is detected by ultrasound during the second trimester, conservative management via strict observation alone is also feasible.

Safety and feasibility of trial of labor in pregnant women with cesarean scar diverticulum

OBJECTIVE

Literature on trial of labor after cesarean section (TOLAC) in women with isthmoceles is scarce because of complications associated with the procedure. This study investigated TOLAC's safety and feasibility in patients with isthmoceles.

METHODS

The study group comprised 34 pregnant women with isthmoceles who vaginally delivered. The control group comprised 102 pregnant women without isthmoceles who vaginally delivered during the same period. Scar diverticula were measured using color Doppler ultrasonography; between-group delivery outcomes were compared.

RESULTS

Of the study group patients, 27/34 had isthmoceles diagnosed by ultrasound before pregnancy. Nineteen (70.37%) of these patients had mild defects and eight (29.63%) had moderate defects. The scar diverticula's mean length, depth, and width were 1.05 ± 0.62, 0.54 ± 0.28, and 1.20 ± 0.70 cm, respectively. The residual muscle layer's mean thickness was 0.27 ± 0.07 cm. The mean diverticulum depth/residual muscular thickness ratio was 2.39 ± 2.58. The duration of the first stage of labor was significantly shorter and the neonatal weight was significantly lower in the study group than control group.

CONCLUSION

Successful vaginal delivery is possible for women with mild and moderate isthmoceles. Further large-scale studies are needed to improve TOLAC's safety in pregnant women with isthmoceles.

Gynecological outcomes of uterine niche after cesarean section: A descriptive study

Objectives:

Our aim was to study the prevalence of isthmocele in cases with previous cesarean section scar presented to El Shatby maternity university hospital and its association with gynecological complications.

Material and Methods:

After approval of the ethics committee of Alexandria faculty of medicine, a sample of 300 patients delivered by cesarean section since 6 months or more presented by one or more of the following symptoms: Abnormal uterine bleeding (AUB) dysmenorrhea, secondary infertility, and lower abdominal pain were selected from the gynecology clinic of El Shatby maternity university hospital. All patients were subjected to history taking, clinical, and gynecological examination. Post-menstrual 2D transvaginal ultrasonography was done. Where the niche or isthmocele was seen as triangular or dome- shaped echo-free space. Data were collected and entered to the computer using Statistical Package for the Social Science program for statistical analysis.

Results:

Niche was found in 44 cases. Most of them were symptomatic. Duration from the last (CS) was statistically significant. Symptoms were related to number of previous cesarean sections.

Conclusion:

The incidence of post-cesarean section niche in El Shatby Maternity hospital was 14.67%. Most common symptoms were AUB and dyspareunia.

The INTEGRITY Trial: Preservation of Uterine-Wall Integrity 12 Months After Transcervical Fibroid Ablation with the Sonata System

Objective: The aim of this research was to evaluate uterine-wall integrity 12 months after transcervical fibroid ablation (TFA) of uterine fibroids with the Sonata^® system (Gynesonics Inc., Redwood City, CA).

Materials and Methods: INTEGRITY is a secondary analysis of the FAST-EU clinical trial, a prospective, longitudinal, multicenter single-armed trial involving women with heavy menstrual bleeding secondary to fibroids who were treated at 7 academic and community hospitals in the United Kingdom, the Netherlands, and Mexico with transcervical, intrauterine, ultrasound-guided radiofrequency ablation (the Sonata system). TFA was performed on up to 5 fibroids per subject ranging from 1–5 cm in diameter as determined by magnetic resonance imaging (MRI). All measurements and comparisons, including uterine-wall thicknesses were derived from baseline and 12-month MRI scans by an independent core MRI center. Scans were analyzed to assess preservation of uterine-wall integrity and reviewed for uterine-wall anomalies after TFA with the Sonata system.

Results: Twenty-nine patients had baseline and 12-month MRI with contrast enhancement. Minimum uterine-wall thicknesses in all visible slices were >2.5 mm in diameter. No areas on MRI indicated any loss of uterine-wall integrity, compared with baseline imaging; comparison of baseline and postablation uterine-wall thicknesses revealed no significant changes.

Conclusion: Transcervical fibroid ablation with the Sonata system was associated with preservation of uterine-wall integrity in this patient cohort.

Isthmocele: an overview of diagnosis and treatment

An isthmocele, a cesarean scar defect or uterine niche, is any indentation representing myometrial discontinuity or a triangular anechoic defect in the anterior uterine wall, with the base communicating to the uterine cavity, at the site of a previous cesarean section scar. It can be classified as a small or large defect, depending on the wall thickness of the myometrial deficiency. Although usually asymptomatic, its primary symptom is abnormal or postmenstrual bleeding, and chronic pelvic pain may also occur. Infertility, placenta accrete or praevia, scar dehiscence, uterine rupture, and cesarean scar ectopic pregnancy may also appear as complications of this condition. The risk factors of isthmocele proven to date include retroflexed uterus and multiple cesarean sections. Nevertheless, factors such as a lower position of cesarean section, incomplete closure of the hysterotomy, early adhesions of the uterine wall and a genetic predisposition may also contribute to the development of a niche. As there are no definitive criteria for diagnosing an isthmocele, several imaging methods can be used to assess the integrity of the uterine wall and thus diagnose an isthmocele. However, transvaginal ultrasound and saline infusion sonohysterography emerge as specific, sensitive and cost-effective methods to diagnose isthmocele. The treatment includes clinical or surgical management, depending on the size of the defect, the presence of symptoms, the presence of secondary infertility and plans of childbearing. Surgical management includes minimally invasive approaches with sparing techniques such as hysteroscopic, laparoscopic or transvaginal procedures according to the defect size.

Comparison of the lower uterine segment in pregnant women with and without previous cesarean section in 3 T MRI

BACKGROUND

Prenatal risk stratification of women with previous cesarean section (CS) by ultrasound thickness measurement of the lower uterine segment (LUS) is challenging. There is a wide range of proposed cutoff values and a valuable algorithm for selection before birth is not available. Using 3 T magnetic resonance imaging (MRI), we aimed to identify possible shortcomings of the current protocols used for birth selection after CS. Therefore, we evaluated anatomic and morphologic differences of the LUS and its thickness in patients with CS and those without. Possible impact factors on LUS thickness were studied.

METHODS

We retrospectively analyzed 3 T MRI scans of 164 pregnant women in their second or third trimester, with (patient group, n = 60) and without previous CS (control group, n = 104). Sagittal T2-weighted images were studied. Normal findings of the LUS in MRI, reliability of MRI measurements, as well as factors influencing LUS thickness were assessed. MRI findings were compared to intraoperative findings.

RESULTS

MRI provided good intra- (ICC 0.872) and fair inter-rater reliability (ICC 0.643). The relationship of the LUS and the cesarean scar to the surrounding anatomical structures and also its morphology varied strongly in patients and controls. Scar identification was possible in only 9/60 (15.0%) patients. The LUS was thinner in patients (1.9 ± 0.7 mm) than in controls (2.7 ± 1.3 mm). An LUS thinning up to 1 mm was observed in 23% of women without a previous CS and in 34% of women with normal intraoperative findings. Suspicion of a uterine dehiscence (LUS thickness < 1 mm) was only found in the patient group (5/59 (8.5%)) and was intraoperatively confirmed. In controls, LUS thickness was influenced by fetal weight, gestational age and amniotic fluid amounts.

CONCLUSION

Variability in anatomy, thickness and morphology seem to limit common prenatal LUS imaging diagnostics. Therefore, we consider that diagnostic protocols must be re-evaluated and imaging should be adjusted to the individual patient conditions. Due to its independency of ultrasound limitations, an additional MRI might be useful for altered anatomy and impaired ultrasound conditions. An LUS thinning up to 1 mm might be a normal finding and should be further investigated as reference value.

Comparative accuracy of magnetic resonance morphometry and sonography in assessment of post-cesarean uterine scar

Objective

To compare the diagnostic accuracy of magnetic resonance imaging (MRI) with that of ultrasonography (USG) for the measurement of lower segment cesarean scar during trial of labor after cesarean (TOLAC).

Materials and Methods

This was a prospective case-control observational study conducted with a cohort of 30 participants being considered for TOLAC but eventually proceeding to lower segment cesarean section (LSCS) at a university-based teaching institute over a period of 2 years. Measurement of scar thicknesses were done by MRI and USG preoperatively and validated by surgical findings. Comparison of diagnostic accuracy as well as the cut-off values (to differentiate a normal scar from an abnormal scar) was done between the two modalities.

Results

Insignificant systematic error between the measurements obtained by the two modalities was noted by a Bland-Altmann analysis. The diagnostic accuracy of USG for differentiating a normal from an abnormal uterine scar was 96.7% while that of MRI was at a slightly lower level of 90%. A strong level of agreement between the two modalities was observed.

Conclusion

MRI offers no advantage in diagnostic accuracy for the measurement of LSCS scar thickness during consideration of TOLAC.

Advances in Knowledge

Measurement of uterine scar by MRI has a good correlation with that done on USG in the setting of post-cesarean pregnancy. The results hold good both for normal (grades 1 and 2) and abnormal (grades 3) scars. MRI, however, does not offer any added advantage over sonographic scar thickness measurement for the differentiation of a normal (grades 1 and 2) from an abnormal (grade 3) scar.

Uterine rupture at 28 weeks of gestation after laparoscopic myomectomy - a case report

There are many reasons for sterility, and uterine malformations are of the greatest concern. Among uterine disorders, myomas play a significant role and are present in 27% of infertile women. The occurrence of myomas is frequent - 20-40% in women of reproductive age. Thus, for those infertile patients surgical treatment may be needed to preserve an opportunity to conceive. This case report refers to an uterine rupture at 28 weeks of gestation after laparoscopic myomectomy (3 months before conceiving). The myomectomy was conducted correctly and two layers of sutures on the myometrium were performed. The purpose of the myomectomy in a young woman should be well considered. In cases of infertility, removal of the lesions is usually necessary to give the patient a chance of pregnancy. At the same time, the risk of uterine rupture is increased. There are some suggestions referring to myomectomy to reduce the risk of uterine rupture in a subsequent pregnancy. It seems that the method of sewing the uterine closure is crucial. For example, multilayer uterine stitches, preservation of the endometrial cavity, and avoidance of using electrosurgery to prevent devascularization (to avoid haematoma formation) should be taken into consideration to prevent weakness of the wall of the uterus. Uterine scars differ histologically and biochemically.

Utility of multiparametric MRI in Caesarean section scar characterization and preoperative prediction of scar dehiscence: a prospective study

Background Post-Caesarean uterine scar rupture during vaginal birth after Caesarean section (VBAC) is a potentially life-threatening complication. Prediction of scar dehiscence and scar rupture is vital in treatment planning and selecting candidates of trial of labor after a Caesarean section (CS). Purpose To assess the accuracy of magnetic resonance imaging (MRI) for evaluation of post-Caesarean uterine scar and to predict scar dehiscence during repeat CS. Material and Methods Thirty patients with a history of at least one previous CS underwent pelvic MRI for assessment of uterine scar during a subsequent gestation, all of whom underwent lower segment Caesarean section (LSCS) subsequently due to one of the established indications of CSs. Thickness, T1, T2 signal intensity ratio (SER), and apparent diffusion coefficient (ADC) value of scar site were charted. The lower uterine segment was assessed and graded intraoperatively and findings were correlated with MRI findings. Results A total of 30 participants were included in this study, of which nine were classified as having an abnormal scar (of various grades) based on surgical observations. T2 SER with a cutoff value of 0.935 showed the highest sensitivity of 100% and scar thickness value of 3.45 mm showed highest specificity of 91% in prediction of abnormal scar. On drawing a receiver operating characteristic (ROC) curve, T2 signal intensity ratio showed the highest area under the curve (AUC) closely followed by scar thickness values. Conclusion MRI derived parameters may be utilized for differentiation of an abnormal post-Caesarean uterine scar from a normal one. Both scar thickness and T2 SER measured on MRI can be used to predict scar dehiscence. However, T2 SER can serve as a more standardized and objective criterion.

Ultrasound Assessment of Lower Uterine Segment Thickness During Pregnancy, Labour, and the Postpartum Period

OBJECTIVES

To evaluate the normal ranges of lower uterine segment (LUS) thickness throughout pregnancy in women without a previous cesarean and to evaluate the relationship between ultrasound and intraoperative LUS thickness.

METHODS

We assessed LUS thickness using transabdominal and transperineal longitudinal scan at each week of gestation, during labour, and in the postpartum period in 1000 pregnant women without previous CS. Secondly, we assessed LUS thickness immediately before CS (using ultrasound) and intraoperatively (using ophthalmic calipers) immediately before delivery of the fetus in 35 women with a previous CS and 29 women without previous CS undergoing elective CS before labour.

RESULTS

We performed 20 307 LUS thickness measurements in between 119 and 944 women at each week of gestation, in 944 women during labour, and in 936 women after delivery. We observed a strong relationship between transabdominal and transperineal ultrasound (P < 0.001) and an inverse correlation between LUS thickness and gestational age (P < 0.001), with a mean thickness of 5.1 ± 1.4 mm at 20 weeks, 3.6 ± 1.3 mm at 30 weeks, and 2.3 ± 0.6 mm at 40 weeks of gestation. In women undergoing elective CS, we observed a strong relationship between antepartum and intraoperative LUS thickness (P < 0.001), with mean thicknesses of 2.2 ± 0.7 mm in 28 women without thinning of LUS; 0.8 ± 0.1 mm in four women with grade II uterine scar dehiscence; and 0.4 ± 0.1 mm in three women with grade III dehiscence. A LUS myometrial thickness less than 1.2 mm could have predicted all grade II and grade III uterine scar dehiscences without false-positive cases.

CONCLUSION

LUS thickness decreases with gestational age and correlates strongly with the intraoperative LUS thickness in women with a previous CS.

Sonographic prediction of scar dehiscence in women with previous cesarean section

PURPOSE

To estimate the risk of uterine dehiscence/rupture in women with previous cesarean section (CS) by comparing the thickness of lower uterine segment (LUS) and myometrium with trans-abdominal (TAS) and trans-vaginal sonography (TVS).

METHOD

In this case-control study, in 100 pregnant women posted for elective CS (with or without previous CS; group 1 and group 2 respectively), the thickness of LUS and myometrium was measured sonographically (TAS and TVS). Intra-operatively, LUS was graded (grades I-IV), and its thickness was measured with calipers. The primary outcome of the study was correlation between echographic measurements (TAS and TVS) and features of LUS (grades I-IV) at the time of CS. Secondary outcomes were correlation between myometrial thickness, number of previous CS, and inter-delivery interval with LUS (grades I-IV).

RESULTS

Sonographic measurements of LUS and myometrium were significantly different between the two groups (both TAS and TVS p value = 0.000 each). However, the number of previous CS (p = 0.440) and inter-delivery interval (p = 0.062) had no statistically significant correlation with thickness of LUS.

CONCLUSIONS

Sonographic evaluation of LUS scar and myometrial thickness (both with TAS and TVS) is a safe, reliable, and non-invasive method for predicting the risk of scar dehiscence/rupture. Specific guidelines for TOLAC, after sonographic assessment of women with previous CS, are need of the hour.

Variables influencing the integrity of lower uterine segment in post-cesarean pregnancy

BACKGROUND

There is significant increase in proportion of cases with previous cesarean delivery requiring obstetric care. The available literature fails to provide uniform opinion on each woman's characteristics to identify risk of uterine rupture while planning trial of labor after cesarean.

OBJECTIVE

To study the association of abnormal lower uterine segment with some of the present and previous obstetric variables including patient characteristics and surgical techniques at previous cesarean operation.

MATERIALS AND METHODS

Consenting consecutive 96 post-cesarean singleton pregnancies admitting after 36 weeks gestation at the same facility from July 2011 to December 2012 for repeat cesarean, were studied. Only the cases with cephalic presentation and vertex as presenting part, having no placenta previa, polyhydramnios, uterine anomaly or fibroid and those who had previous one lower segment cesarean were recruited. Based on the intra-operative finding the lower uterine segment (LUS) was categorized into those having a normal and abnormal (grades 2-4) LUS. Sonographic assessment of LUS thickness and any abnormalities if any were noted. The findings of abnormal LUS (direct observation at surgery and sonographic impression within a week before surgery) were looked for association with some of the present and previous obstetric variables including patient characteristics and surgical techniques at previous cesarean operation using Student t, Chi square or Fisher's exact test for analysis as appropriate. Receiver operating curve analysis was used to determine the optimal cut off value for prediction of LUS integrity by ultrasound.

RESULTS

Of the women recruited for the study, 36 were admitted in early labor and ultrasound evaluation of LUS was performed in 48 of the remaining 60 women admitted antenatal for elective cesarean delivery. There were 38 abnormal LUS (39.6%) with 22 of them (57.9%) graded as 'thinned out LUS'. The incidence of scar dehiscence (grade 3, cases 5) was 5.2% of 96 cases and there were no cases of scar rupture. Proportion of cases with abnormal LUS was significantly high when primary cesarean was done in preterm (p = 0.02); it was a single layer uterine closure (p = 0.02), and inter-cesarean interval was 54 months (p = 0.01). Abnormal LUS was also seen to be associated with maternal age beyond 35 years (p = 0.2), when cesarean was performed in labor (p = 0.5), following 18 h of rupture of membranes (p = 0.75), for a baby weight more than 3 kg (p = 0.4), and different suture materials (polyglactin 910 and chromic catgut) were used to close uterus at primary cesarean delivery (p = 0.1), and also if they had post-partum fever (p = 0.3). Ultrasound measurement of LUS by abdominal scan correlated with the intra-operative LUS grading and a thickness of more than 3.2 mm within a week before delivery and was seen to be the safe cut off above which most of the women had a normal LUS (sensitivity 92.3%, specificity 81.1%).

CONCLUSION

Factors at primary cesarean operation significantly influence the state of LUS at term in subsequent pregnancy .

Sonographic measurement of lower uterine segment thickness to predict uterine rupture during a trial of labor in women with previous Cesarean section: a meta-analysis

OBJECTIVE

To evaluate the accuracy of antenatal sonographic measurement of lower uterine segment (LUS) thickness in the prediction of risk of uterine rupture during a trial of labor (TOL) in women with a previous Cesarean section (CS).

METHODS

PubMed and EMBASE were searched to identify articles published on the subject of sonographic LUS measurement and occurrence of a uterine defect after delivery. Four independent researchers performed identification of papers and data extraction. Selected studies were scored on methodological quality, and sensitivity and specificity of measurement of LUS thickness in the prediction of a uterine defect were calculated. We performed bivariate meta-analysis to estimate summary receiver-operating characteristics (sROC) curves.

RESULTS

We included 21 studies with a total of 2776 analyzed patients. The quality of included studies was good, although comparison was difficult because of heterogeneity. The estimated sROC curves showed that measurement of LUS thickness seems promising in the prediction of occurrence of uterine defects (dehiscence and rupture) in the uterine wall. The pooled sensitivity and specificity of myometrial LUS thickness for cut-offs between 0.6 and 2.0 mm was 0.76 (95% CI, 0.60-0.87) and 0.92 (95% CI, 0.82-0.97); cut-offs between 2.1 and 4.0 mm reached a sensitivity and specificity of 0.94 (95% CI, 0.81-0.98) and 0.64 (95% CI, 0.26-0.90). The pooled sensitivity and specificity of full LUS thickness for cut-offs between 2.0 and 3.0 mm was 0.61 (95% CI, 0.42-0.77) and 0.91 (95% CI, 0.80-0.96); cut-offs between 3.1 and 5.1 mm reached a sensitivity and specificity of 0.96 (95% CI, 0.89-0.98) and 0.63 (95% CI, 0.30-0.87).

CONCLUSIONS

This meta-analysis provides support for the use of antenatal LUS measurements in the prediction of a uterine defect during TOL. Clinical applicability should be assessed in prospective observational studies using a standardized method of measurement.

Changes in Cesarean section scar dimensions during pregnancy: a prospective longitudinal study

OBJECTIVES

To describe changes in Cesarean section (CS) scars longitudinally throughout pregnancy, and to relate initial scar measurements, demographic variables and obstetric variables to subsequent changes in scar features and to final pregnancy outcome.

METHODS

In this prospective observational study we used transvaginal sonography (TVS) to examine the CS scar of 320 consecutive pregnant women at 11-13, 19-21 and 32-34 weeks' gestation. For scars visible on TVS, the hypoechoic part was measured in three dimensions and the residual myometrial thickness (RMT) was also measured. Analyses were carried out using one-way repeated measures ANOVA and mixed modeling. The incidence of subsequent scar rupture was recorded.

RESULTS

The CS scar was visible in 284/320 cases (89%). Concerning length and depth of the hypoechoic part of the scar and RMT, the larger the initial scar measurement, the larger the decrease observed during pregnancy. For the hypoechoic part of the scar, the width increased on average by 1.8 mm per trimester, while the depth and length decreased by 1.8 and 1.9 mm, respectively (false discovery rate P < 0.0001). Mean RMT in the first trimester was 5.2 mm and on average decreased by 1.1 mm per trimester. Two cases (0.62%) of uterine scar rupture were confirmed following a trial of vaginal delivery; these had a mean RMT of 0.5 mm at second scan and an average decrease of 2.6 mm over the course of pregnancy.

CONCLUSION

This study establishes reference data and confirms that the dimensions of CS scars change throughout pregnancy. Scar rupture was associated with a smaller RMT and greater decrease in RMT during pregnancy. There is the potential to test absolute values and observed changes in CS scar measurements as predictors of uterine scar rupture and outcome in trials of vaginal birth after Cesarean section.

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%).

Standardized approach for imaging and measuring Cesarean section scars using ultrasonography

Incomplete healing of the scar is a recognized sequel of Cesarean section (CS) and may be associated with complications in later pregnancies. These complications can include scar pregnancy, a morbidly adherent placenta, scar dehiscence or rupture. To date there is uncertainty relating to the factors that lead to poor scar healing and how to recognize it. In recent years, there has been an increase in studies using ultrasound that describe scars as deficient, or poorly, incompletely or inadequately healed with few data to associate the morphology of the scar with the functional integrity of the lower segment of the uterus. There have been multiple attempts to describe CS scars using ultrasonography. Different terminology, methods and results have been reported, yet there is still no consensus regarding the prevalence, clinical significance or most appropriate method to describe the appearances of these scars. Developing a test that can predict the likelihood of women having problems associated with a CS scar is becoming increasingly important. On the other hand, understanding whether the ultrasound appearances of the scar can tell us anything about its integrity is not well supported by the research evidence. In this article we present an overview of ultrasound-based definitions and methods used to describe CS scars. We also present information relating to the performance of alternative techniques used to evaluate CS scars. Having examined the current evidence we suggest a standardized approach to describe CS scars using ultrasound so that future studies can be meaningfully compared.

Findings in patients with postmenstrual spotting with prior cesarean section

STUDY OBJECTIVE

Throughout the years, patients previously submitted to C-sections may have abnormal uterine bleeding (AUB) of the post-menstrual spotting type. This symptom has been correlated to an anatomical defect on the anterior uterine wall. The objective of the present investigation was to assess the hysteroscopy findings of women at reproductive age, previously submitted to cesarean sections and complaining of post-menstrual spotting, stressing the diagnosis of isthmocele.

DESIGN

Prospective study (Canadian Task Force II).

SETTING

State public hospital-Department of Gynecological Endoscopy.

PATIENTS

Forty-three patients at reproductive age previously submitted to one or more cesarean sections, complaining of AUB of the post-menstrual spotting type, were submitted to diagnostic hysteroscopy in order to assess the presence of anterior uterine wall isthmocele.

INTERVENTIONS

Hysteroscopic diagnoses.

MEASUREMENTS AND MAIN RESULTS

The mean number of previous C-sections was 2, the average time of post-menstrual spotting observation was 6 years and the mean duration of each episode was 6 days. The hysteroscopic diagnosis of isthmocele was conclusive in 38 patients (88.37%).

CONCLUSION

Patients with previous C-sections complaining of postmenstrual spotting type of AUB have a high prevalence of isthmocele, and this condition is likely diagnosed through diagnostic hysteroscopy.

Lower uterine segment thickness measurement in pregnant women with previous Cesarean section: reliability analysis using two- and three-dimensional transabdominal and transvaginal ultrasound

OBJECTIVE

To evaluate the reliability of two- and three-dimensional ultrasonographic measurement of the thickness of the lower uterine segment (LUS) in pregnant women by transvaginal and transabdominal approaches.

METHODS

This was a study of 30 pregnant women who had had at least one previous Cesarean section and were between 36 and 39 weeks' gestation, with singleton pregnancies in cephalic presentation. Sonographic examinations were performed by two observers using both 4-7-MHz transabdominal and 5-8-MHz transvaginal volumetric probes. LUS measurements were performed using two- and three-dimensional ultrasound, evaluating the entire LUS thickness transabdominally and the LUS muscular thickness transvaginally. Each observer measured the LUS four times by each method. Reliability was analyzed by comparing the mean of the absolute differences, the intraclass correlation coefficients, the 95% limits of agreement and the proportion of differences < 1 mm.

RESULTS

Transvaginal ultrasound provided greater reliability in LUS measurements than did transabdominal ultrasound. The use of three-dimensional ultrasound improved significantly the reliability of the LUS muscular thickness measurement obtained transvaginally.

CONCLUSIONS

Ultrasonographic measurement of the LUS muscular thickness transvaginally appears more reliable than does that of the entire LUS thickness transabdominally. The use of three-dimensional ultrasound should be considered to improve measurement reliability.

Vaginal Ultrasonographic and Hysterosonographic Evaluation of the Low Transverse Incision after Caesarean Section: Correlation with Gynaecological Symptoms

AIM

We investigated whether there is a correlation between morphological changes of the lower uterine segment after caesarean section (CS), visualized by means of either a transvaginal sonography (TVS) or a sonohysterography (SHG), and the frequency of abnormal uterine bleedings reported by the women.

METHODS

By means of a random selection of our population, anamnesis, medical records, and TVS and SHG images of the lower uterine segment were collected in 217 women (116 with previous CS and 101 with previous vaginal birth), and an observational case-control study was performed.

RESULTS

The uterine incision was identified in almost all women after CS (102/116) using TVS. It was observed that abnormal uterine bleeding was significantly more frequent in the CS group in comparison with the group of women who delivered vaginally. A correlation between the presence of abnormal uterine bleeding and the presence of significant sonographic findings in the lower uterine transverse incision in the women after CS was found. In the CS group, TVS findings were confirmed by those obtained by SHG, and, with this technique, a triangular anechoic area at the presumed site of incision (the niche) was identified in 69 of the 116 women (59.5%).

CONCLUSIONS

In this study, we found a correlation between abnormal uterine bleeding and sonographic findings in women after CS. This correlation appears to be more significant in women who had CS 5-10 years ago. A significant difference exists between the CS group and the group of women who delivered vaginally for both frequency of abnormal uterine bleeding and sonographic findings.

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.

Ultrasonographic evaluation of lower uterine segment thickness in patients of previous cesarean section

OBJECTIVE

To evaluate by ultrasonography, the lower uterine segment thickness of women with a previous cesarean delivery and determine a critical thickness above which safe vaginal delivery is predictable.

METHODS

A prospective observational study of 71 antenatal women with previous cesarean delivery and 50 controls was carried out. Transabdominal and transvaginal ultrasonography were used in both groups to evaluate lower uterine segment thickness. The obstetric outcome in patients with successful vaginal birth and intraoperative findings in women undergoing cesarean delivery were correlated with lower segment thickness.

RESULTS

The overall vaginal birth after cesarean section (VBAC) was 46.5% and VBAC success rate was 63.5%, the incidence of dehiscence was 2.82%, and there were no uterine ruptures. There was a 96% correlation between transabdominal ultrasonography with magnification and transvaginal ultrasonography. The critical cutoff value for safe lower segment thickness, derived from the receiver operator characteristic curve, was 2.5 mm.

CONCLUSION

Ultrasonographic evaluation permits better assessment of the risk of scar complication intrapartum, and could allow for safer management of delivery.

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.

Preoperative diagnosis of dehiscence of the lower uterine segment in patients with a single previous Caesarean section

Preoperative diagnoses were checked during surgery in 39 patients who underwent elective repeat Caesarean section with (n = 20) and without (as control, n = 19) a preoperative diagnosis of wall dehiscence (thinning) of the lower uterine segment (LUS). All patients were examined manually and by ultrasonography at 36 weeks gestation before labour. A preoperative diagnosis of wall dehiscence was made when the wall thickness was less than 2 mm and/or the patient felt pain and tenderness in the LUS. Surgical findings of dehiscence were defined as a subperitoneal separation of the uterine scar in the LUS. The sensitivity and specificity of our ultrasonographic evaluations were found to be 100% and 83% (p < 0.05), respectively. On the other hand, there were no surgical findings of dehiscence in patients who felt pain and tenderness in the LUS with a wall thickness greater than 2 mm, nor among those in the control group.

Prediction of uterine dehiscence by measuring lower uterine segment thickness prior to the onset of labor: evaluation by transvaginal ultrasonography

OBJECTIVE

Lower uterine segment thickness was measured by transvaginal ultrasound examination and its correlations with the occurrence of uterine dehiscence and rupture was examined.

METHODS

The thickness of the muscular layer of the lower uterine segment was measured in 186 term gravidas with previous uterine scars and its correlation with uterine dehiscence/rupture was investigated.

RESULTS

Uterine dehiscence was found in 9 cases or 4.7%. There were no cases of the uterine rupture. The thickness of the lower uterine segment among the gravidas with dehiscence was significantly less in than those without dehiscence (p< 0.01). The cut-off value for the thickness of the lower uterine segment was 1.6 mm as calculated by the receiver operating characteristic curve. The sensitivity was 77.8%; specificity 88.6%; positive predictive value 25.9%; negative predictive value 98.7%.

CONCLUSION

Measurement of the lower uterine segment is useful in predicting the absence of dehiscence among gravidas with previous cesarean section. If the thickness of the lower uterine segment is more than 1.6 mm, the possibility of dehiscence during the subsequent trials of labor is very small.