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.