Risk factors for incomplete healing of the uterine incision after caesarean section

Objective To determine which factors increase the risk of large caesarean scar defects as assessed by transvaginal ultrasound. Design Observational cross-sectional study. Setting University Hospital. Population One hundred and eight women who had undergone one caesarean section. Methods Transvaginal ultrasound examination of the scar in the uterus 6-9 months after the caesarean. Published ultrasound definitions of large scar defects were used. Clinical information was obtained from medical records after all ultrasound images had been evaluated. Main outcome measures Factors increasing the risk of large caesarean scar defects. Results Twenty-two (20%) women had a large caesarean scar defect. The odds of a large defect increased with cervical dilatation at caesarean (0 cm, 1-4 cm, 5-7 cm, 8 cm or more; odds ratio [OR] 4.4 [95% CI 0.7-28.5]; 26.5 [4.3-161.8]; and 32.4 [6.1-171.0]; P < 0.001), station of the presenting part at caesarean below pelvic inlet (OR 14.1 [4.6-43.1]; P < 0.001), duration of labour at caesarean (0 hour, 1-4 hours, 5-9 hours, 10 hours or more; OR 2.0 [0.2-23.8]; 13.0 [2.2-76.6]; and 33.1 [6.6-166.9]; P < 0.001), oxytocin augmentation (OR 6.3, [2.3-17.3]; P < 0.001), retroflexed uterus at ultrasound examination (OR 2.9 [1.0-8.3]; P = 0.047). According to multivariate logistic regression no variable added information to cervical dilatation or the station of the presenting fetal part at caesarean. Conclusions Caesarean in advanced labour is associated with increased risk of incomplete healing of the uterine incision as determined by transvaginal ultrasound.