Prediction of cesarean section scars with ultrasound imaging during pregnancy.

We sought to determine whether a sonographic examination could identify uterine scars in patients with a history of previous cesarean section and further distinguish patients having previous low transverse from vertical uterine incisions. Forty-six antenatal obstetrical patients with a history of prior cesarean section(s) and 30 control patients without prior uterine surgery underwent sonogram examinations to identify the scar. The researcher who later reviewed the sonogram was blinded as to the presence or type of uterine scar. Of the 47 scars examined, uterine scars were visualized in 13 (27.7%). All scars seen were low transverse; no vertical scars were identified by sonography (p less than .05). No scars were visualized with sonography in the control group and cesarean section scars were seen more easily prior to the third trimester. No information concerning the scar condition (dehiscence) could be obtained with sonography. We conclude it is of benefit to perform sonogram exams in patients with prior cesarean sections of unknown incision to better counsel them as to their risk to rupture. Although vertical cesarean section scars could not be visualized, those patients who had low transverse scars identified could be included in a low-risk vaginal birth population.