Ultrasound examination of caesarean section scars during pregnancy.

Two hundred and sixteen transverse caesarean section scars were examined sonographically near term by a conventional method (175 scars) and a new method (41 scars). The new method consisted of obtaining a transabdominal longitudinal scan by the conventional method and also by a 3M conductor, a transabdominal frontal scan to give a surface view of the scar, and transperineal and transvaginal longitudinal scans. The new method was used from 16 weeks of gestation onwards. Of 41 scars scanned by the new method, 31 showed good healing, being more than 2 mm in thickness throughout; 10 scars showed poor healing with a thickness of less than 2 mm and loss of continuity. Of 31 patients with good healing, 8 delivered vaginally and the remaining 23 patients had repeat caesarean sections for other obstetric indications. All patients with ultrasound evidence of poor healing had repeat caesarean sections. At operation the thickness of the lower uterine segment was measured with ophthalmic calipers. There were 4 false negative results (4/83: 4.8%) and 1 false positive result (1/43: 2.3%) with conventional ultrasound and no false positives or false negatives with the new method.