Cesarean section scar as a cause of abnormal vaginal bleeding: diagnosis by sonohysterography.

A previously undescribed cause of abnormal uterine bleeding is presented. Nine of 310 women evaluated by sonohysterography for abnormal bleeding demonstrated an 8 to 17 mm gap in the anterior lower uterine segment myometrium at the site of prior cesarean deliveries. All women were premenopausal and had a history of 2 to 12 days of postmenstrual spotting. Presumably a lack of coordinated muscular contractions occurs around the cesarean scar, allowing the defect to collect menstrual debris. Subsequently, the debris leaches out through the cervix for several days after the majority of menstrual flow has ceased.