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 whether double-layer uterine closure after a first caesarean section (CS) is superior compared with 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: Thirty-two hospitals in the Netherlands. POPULATION: A total of 2292 women aged ≥18 years undergoing a first CS were randomly assigned to each procedure (1:1): 1144 women were assigned to single-layer uterine closure and 1148 women were assigned to double-layer uterine 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 9 months after CS. SECONDARY OUTCOMES: perioperative and menstrual characteristics; transvaginal ultrasound measurements. RESULTS: A total of 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, as a result of drop-out and amenorrhoea. The mean number of postmenstrual spotting days was 1.33 (bootstrapped 95% CI 1.12-1.54) after single-layer closure and 1.26 (bootstrapped 95% CI 1.07-1.45) after double-layer closure (adjusted mean difference -0.07, 95% CI -0.37 to 0.22, P = 0.810). The operative time was 3.9 minutes longer (95% CI 3.0-4.9 minutes, P < 0.001) and niche prevalence was 4.7% higher (95% CI 0.7-8.7%, P = 0.022) after double-layer closure. CONCLUSIONS: The superiority of double-layer closure compared with 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. TWEETABLE ABSTRACT: Double-layer uterine closure is not superior for postmenstrual spotting after a first caesarean; single-layer closure performs slightly better on other outcomes.