1. UOG Journal Club: April 2016 Impact of adding a second layer to a single unlocked closure of a Cesarean uterine incision: randomized controlled trial G. Bennich, M. Rudnicki, C. Wilken-Jensen, T. Lousen, P.D. Lassen and K. Wojdemann Journal Club slides prepared by Dr. Katherine Goetzinger (UOG Editor for Trainees)

2. Impact of adding a second layer to a single unlocked closure of a Cesarean uterine incision: randomized controlled trial Bennich et al., UOG 2016 Although Cesarean section is one of the most commonly performed surgical procedures, there is a paucity of high quality evidence to support many technical aspects of the procedure Existing data are conflicting over the role of single vs. double layer uterine closure and locking vs. unlocking technique in the prevention of uterine rupture in a subsequent pregnancy Given that uterine rupture is a rare event, attention has turned to sonographic measurement of residual myometrial thickness (RMT) as a surrogate marker for this catastrophic event

3. To investigate uterine scar thickness in patients randomized to receive a single- or double-layer closure of the Cesarean section incision when an unlocked technique is used Objective Impact of adding a second layer to a single unlocked closure of a Cesarean uterine incision: randomized controlled trial Bennich et al., UOG 2016

4. Inclusion Criteria: Scheduled term (>37 weeks) elective Cesarean section, singleton first-time delivery without preterm rupture of membranes, contractions or cervical dilation Exclusion Criteria: Previous uterine surgery, fibroids in the cervical or cervical-corporeal border, inflammatory bowel disease, lupus, rheumatoid arthritis, insulin-dependent diabetes, need for three additional single sutures for hemostasis, need for re-operation Study Groups: Patients randomized in 1:1 ratio to either single-layer or double-layer unlocked uterine closure Methodology Randomized Double-Blind Controlled Trial Impact of adding a second layer to a single unlocked closure of a Cesarean uterine incision: randomized controlled trial Bennich et al., UOG 2016

5. Protocol: Cesarean deliveries performed in a standardized fashion by the same 4 trained surgeons Evaluation of lower uterine segment by: Transabdominal ultrasound prior to discharge Transvaginal ultrasound with saline infusion at 5 month visit Outcome: Measurement of residual myometrial thickness at the level of the Cesarean section scar Measurement of total myometrial thickness measured adjacent to the Cesarean section scar to be used for comparison Methodology Impact of adding a second layer to a single unlocked closure of a Cesarean uterine incision: randomized controlled trial Bennich et al., UOG 2016

6. Impact of adding a second layer to a single unlocked closure of a Cesarean uterine incision: randomized controlled trial Bennich et al., UOG 2016 Results

7. Impact of adding a second layer to a single unlocked closure of a Cesarean uterine incision: randomized controlled trial Bennich et al., UOG 2016 Results There was no difference in patient demographics or perioperative characteristics between study groups Mean RMT was similar between single- and double-layer closure groups at both ultrasound exams Mean RMT was similar between the two study groups when assessed by severity of the uterine scar defect at 5 months There was no difference in return to menstruation or pain intensity score between the two groups

8. Impact of adding a second layer to a single unlocked closure of a Cesarean uterine incision: randomized controlled trial Bennich et al., UOG 2016 Results Ultrasound Finding Single Layer Double Layer p Prevalence of Niche First US Second US 82.4% 100% 71.4% 96.9% 0.25 1.0 RMT (mm) First US Second US 20.2 ± 8.0 5.7 ± 2.9 21.0 ± 9.7 5.7 ± 2.2 0.73 0.96 RMT as proportion of anterior wall thickness (%) First US Second US 56.8 ± 17.6 48.1 ± 18.5 58.2 ± 17.7 48.9 ± 16.6 0.76 0.85

9. Conclusions There was no increase in the thickness of the uterine scar (RMT), either immediately postpartum or after 5 months, when a second layer was added to a single unlocked uterine closure. This is in contrast to prior studies demonstrating a decrease in RMT with a single-layer locked uterine closure Myometrial thickness at the level of the scar was only half that of unscarred myometrium in both women receiving a single vs. double layer unlocked closure These findings suggest that a single-layer unlocked uterine closure is as good as a double-layer unlocked closure in uterine healing and reducing the risk of uterine rupture in a subsequent pregnancy Impact of adding a second layer to a single unlocked closure of a Cesarean uterine incision: randomized controlled trial Bennich et al., UOG 2016

10. Randomized, double-blinded study design Standardized surgical technique performed by the same four trained surgeons Inclusion of only pre-labor Cesarean sections Low loss to follow up rate Strengths Impact of adding a second layer to a single unlocked closure of a Cesarean uterine incision: randomized controlled trial Bennich et al., UOG 2016 Use of RMT as a surrogate marker for uterine rupture Small sample size with potential for Type II error Intention to treat analysis not practical Long term follow up unavailable Limitations

11. Discussion Points Impact of adding a second layer to a single unlocked closure of a Cesarean uterine incision: randomized controlled trial Bennich et al., UOG 2016 Are there any immediate intra-operative benefits of using a locked vs. unlocked uterine closure technique? Why did the authors choose to include only those patients presenting for scheduled Cesarean section without labor or rupture of membranes? How may the results have been different if laboring Cesarean sections were included? What are the pros and cons of using RMT as a surrogate marker for uterine rupture? What is intention-to-treat analysis, and why is this important in the analysis of randomized controlled trials? What is the ideal length of follow up to determine RMT after Cesarean section? Will the results of this study alter your Cesarean section operative technique?