Effect of single‐ versus double‐layer uterine closure during caesarean section on postmenstrual spotting (2Close): multicentre, double‐blind, randomised controlled superiority trial

OBJECTIVE To evaluate if double-layer uterine closure after a first caesarean section (CS) is superior compared to single-layer uterine closure in terms of postmenstrual spotting and niche development in the uterine caesarean scar. DESIGN Multicentre, double-blind, randomised controlled superiority trial SETTING: 32 hospitals in the Netherlands. POPULATION 2292 women ≥ 18 years undergoing a first CS were randomly assigned (1:1). 1144 women were assigned to single-layer and 1148 to double-layer closure. METHODS Single-layer unlocked closure and double-layer unlocked closure with the second layer imbricating the first. MAIN OUTCOME MEASURES Number of days with postmenstrual spotting during one menstrual cycle nine months after CS. SECONDARY OUTCOMES perioperative and menstrual characteristics, transvaginal ultrasound measurements. RESULTS 774 (67.7%) women from the single-layer group and 770 (67.1%) women from the double-layer group were evaluable for the primary outcome due to drop-out and amenorrhoea. Mean number of postmenstrual spotting days was 1.33 (bootstrapped 95% CI 1.12 to 1.54) after single-layer and 1.26 (bootstrapped 95% CI 1.07 to 1.45) after double-layer closure (adjusted mean difference -0.07 [95% CI -0.37 to 0.22], p=0.810). Operative time was 3.9 minutes longer (95% CI 3.0 to 4.9, p<0.001) and niche prevalence was 4.8% higher (95% CI 0.01 to 0.09, p=0.027) after double-layer closure. CONCLUSIONS Superiority of double-layer compared to single-layer closure in terms of postmenstrual spotting after a first CS was not shown. Long-term obstetric follow-up of our trial is needed to assess whether uterine caesarean closure guidelines should be adapted.