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ACTA Obstetricia et Gynecologica - PowerPoint Presentation

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ACTA Obstetricia et Gynecologica - PPT Presentation

Scandinavica Journal Club July 2019 Sonographic lower uterine segment thickness after prior cesarean section to predict uterine rupture A systematic review and metaanalysis Brenna E Swift ID: 780200

studies uterine section cesarean uterine studies cesarean section segment rupture thickness ultrasound women delivery labor trial tolac test dehiscence

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Presentation Transcript

Slide1

ACTA

Obstetricia et Gynecologica Scandinavica Journal ClubJuly 2019

Sonographic lower uterine segment thickness after prior cesarean section to predict uterine rupture: A systematic review and meta-analysis

Brenna E. Swift

1,2

| Prakesh S. Shah3,4 | Dan Farine1,21: Department of Obstetrics and Gynecology, Mount Sinai Hospital, Toronto, ON, Canada; 2; Department of Obstetrics and Gynecology, Faculty of Medicine, University of Toronto, Toronto, ON, Canada; 3: Department of Neonatology, Mount Sinai Hospital, Toronto, ON, Canada; 4: Department of Pediatrics, Faculty of Medicine, University of Toronto, Toronto, ON, Canada

Edited

by Francesco D’Antonio

Slide2

Introduction

Successful vaginal birth after cesarean section (VBAC) can be accomplished in about 70.4% after one and in 51.4% after two or more cesarean section according to recent studies.

Despite this, the rate of trial of labour after cesarean section (TOLAC) has decreased significantly in recent years.

The dramatic decrease in TOLAC may be associated with fear of potential complications—the most serious being uterine rupture. The risk of uterine rupture is 0.52% for women who go into spontaneous labor, 0.77% for women with labor induced without prostaglandin and 2.45% for labor induced with prostaglandins.

Factors affecting risk, including 1- or 2-layer uterine closure, inter-delivery interval, number of previous cesarean sections and previous vaginal delivery, are debated in the literature, but definitive guidance for clinical decision-making is not provided.

Several prospective cohort studies have defined a cut-off value for sonographic measurement of the lower uterine segment thickness in pregnant women with a previous cesarean section, because the thickness of the uterine wall may predict likelihood of rupture in cases of TOLAC. 8 However, the ultrasound methodology differs among these studies and therefore the recommended cut-off values differ.

Slide3

Aim

of the studyTo systematically review the predictive characteristics of sonographic measurement of lower uterine segment thickness for uterine rupture during labor.

Slide4

Study design:

Systematic review and meta-analysis.

Index test:

Ultrasound measurement of the lower uterine segment during pregnancy.

Reference test: Delivery outcome and grading of the lower uterine segment thickness at the time of repeat cesarean section.Primary outcome measure: Uterine rupture, defined as direct communication between the amniotic cavity and the peritoneal cavity, if trial of labor was attempted.Secondary outcome measure: Uterine dehiscence, defined as an asymptomatic uterine defect most commonly seen at the time of repeat cesarean section.

Inclusion criteria

:

Studies that assessed the lower uterine segment by ultrasound during pregnancy in women with a previous cesarean section and correlated the ultrasound measurement cut-off with delivery outcome.

Exclusion criteria

:

Case reports, review articles or conference abstracts.

Quality assessment:

Quality assessment of the

included studies was performed using QUADAS-2 tool. This tool uses signaling questions to assist with identifying risk of bias and applicability in the domains of patient selection, index test, reference standard, and flow and timing in the included studies

Material

and

Methods

Slide5

Statistical

analysis: Positive and negative likelihood ratios, diagnostic odds ratio and sensitivity and specificity were calculated for all groups. For the largest groups, the data were plotted as a summary receiver-operating characteristics (SROC) curve, using the hierarchical SROC model.

Material and Methods

Slide6

Results

28 studies were included in the systematic review.All included studies measured the lower uterine segment by ultrasound at term, with a partially full or full bladder, in either the sagittal or transverse scanning plane.

In all the studies was that the timing of the last ultrasound measurement (index test) and delivery (reference standard) was within 5 weeks.There was risk of bias, as some studies used a predefined threshold compared with other studies that calculated the threshold from receiver operator curves. There was also concern for the applicability of the index tests used across the studies, as the ultrasound methods varied considerably among studies.In addition, the reference standard among all studies was delivery; however, some studies allowed trial of labor to test for uterine rupture, whereas, in other studies dehiscence at the time of repeat cesarean section was used as a surrogate marker for uterine rupture

Slide7

Results

All studies showed a correlation between a thin lower uterine segment measured on ultrasound and dehiscence or uterine rupture, except for one study.Women had a TOLAC in 15/28 (53.6%) studies, and the measured outcomes were successful VBAC, uterine rupture or a grading system of uterine dehiscence at either emergent or elective repeat cesarean section. The remaining (13/28) (46.4%) studies used a grading system of uterine dehiscence and/or caliper measurement at elective repeat cesarean section without offering a trial of labor.

The cut-off value ranged from 1.5 to 4.05 mm across all studies. This large range is possibly due to differing ultrasound methodologies used in different studies. Full lower uterine segment thickness is defined as the sum of the myometrial to bladder wall thickness, which also includes the uterine decidua and serosa. In comparison, the myometrial thickness specifically measures the muscular layer of the uterus

Slide8

Results

There were a total of 5874 women in all studies, 20 women were missing delivery information. Trial of labor was attempted in 2680 (45.8%), and 3174 (54.2%) had a repeat elective cesarean section. In the trial of labor group, 1768 (66.0%) women had a vaginal delivery and 912 (34.0%) required an emergency cesarean section. There were 21 cases (0.4%) of uterine rupture reported: 12 women who delivered by emergent cesarean section, five who had a vaginal delivery and four who had an elective cesarean section. There were 361 cases (6.2%) of uterine dehiscence reported in 55 women who delivered by emergent cesarean section, two who had a vaginal delivery and 304 who had an elective cesarean section. The remaining 5472 (93.5%) women had no reported uterine defect at the time of delivery.

For all studies included, the overall sensitivity was 0.854 (95% CI 0.806-0.891) while the specificity was 0.848 (95% CI 0.801-0.886).

Slide9

Results

The SROC curve shows that when measuring the full lower uterine segment thickness by transabdominal ultrasound, the lower uterine segment cut-off thresholds range from 2 to 3.65 mm, the summary point sensitivity was 0.88 (95% CI 0.83-0.92), while specificity was 0.77 (95% CI 0.70-0.83).

When measuring the full lower uterine segment thickness with transvaginal ultrasound, the lower uterine segment cut-off thresholds ranged from 2 to 4.05 mm, the summary point sensitivity was 0.75 (95% CI 0.52-0.97), while specificity was 0.85 (95% CI 0.66-0.96).

Slide10

Limitations

Retrospective design for some of the included studies

Small number of included studies for some of the sub-group analyses.

Concern for the applicability of the index tests used across the studies, as the ultrasound methods varied considerably among studies.

Some studies allowed trial of labor to test for uterine rupture, whereas, in other studies dehiscence at the time of repeat cesarean section was used as a surrogate marker for uterine rupture.

Concern with the reference test in some studies, because there was no blinding of the ultrasound measurements at the time of delivery.

Slide11

Conclusion

A lower uterine segment thickness >3.65 mm is likely safe for TOLAC and a thickness of 2-3.65 mm is probably safe when the clinical criteria for TOLAC are met. A lower uterine segment thickness of <2 mm likely identifies women at a higher risk of uterine rupture.

Ultimately, the decision for TOLAC is a discussion between the woman and her healthcare provider, but lower uterine segment thickness should be used as an additional tool to assist in making an informed decision.