Determinants of residual myometrial thickness after cesarean delivery: Comparative analysis of barbed versus conventional sutures—A sub‐analysis from the SPIRAL trial

Objective: This sub-analysis aimed to determine whether conventional suture-associated risk factors for cesarean scar defect show similar outcomes with barbed continuous suturing, and to identify factors influencing residual myometrial thickness when using barbed continuous sutures.
Methods: This sub-analysis of a multicenter, parallel-group, randomized controlled trial across four Japanese obstetrics and gynecology departments included 1211 women who had their first cesarean delivery between May 2020 and March 2023. Among them, 298 women underwent a C-section, with 253 follow-up through July 2023. Singleton pregnancies were randomly assigned to receive either barbed or conventional double-layered continuous sutures in a 1:1 ratio; they were monitored from consent through their 6- to 7-month check-up. The effects of cervical ripening, facility characteristics, and surgeon experience were investigated using a two-way ANOVA.
Results: Of the remaining 253 patients, 33 were lost to follow-up and 220 completed follow-up (110 per group). One institution enrolled the largest proportion of participants (45.9%), whereas two other institutions had more experienced surgeons. Two-way ANOVA revealed that surgeon experience (P = 0.020) and institutional factors (P < 0.001) significantly influenced the residual myometrial thickness at 6–7 months after surgery, whereas cervical dilation during active labor did not (P = 0.215). Additionally, a significant interaction was observed between institutional factors and suture type (barbed vs. conventional) on residual myometrial thickness (Pinteraction <0.001).
Conclusion: Institutional factors and surgeon experience represent significant determinants of residual myometrial thickness when using barbed sutures for cesarean closure, highlighting the importance of standardized surgical protocols and training across facilities.