[Control of postoperative vaginal sonographic findings following Shirodkar cerclage]

Up to now postoperative control of the uterine cervix following cerclage was performed by bimanual palpation. Since clinical use of transvaginal sonography it is possible to get objective results about preoperative morphology of the cervix (exact cervical length, dilatation of the cervical canal and opening of internal and external os). Besides postoperative vaginal sonography following cerclage can ascertain lengthening and stabilization of the incompetent cervix and localize the ligature's position. 75 pregnant women between 15th and 30th week of gestation were examined using a 5-MHz vaginal sector scanner probe following Shirodkar cerclage to gain information about the residual cervical length and the distance from the surface of the ectocervix to the ligature's position within the anterior and posterior lip of the cervix. The mean postoperative cervical length was 3.75 cm (1.5 cm-6.5 cm). Compared to the preoperative average length of 3.0 cm (0.5 cm-5.0 cm) the cerclage resulted in an increase of about 25%. The average distance from the surface of the ectocervix to the ligature at anterior lip of the cervix was 1.85 cm, ranging from 0.9 cm to 2.6 cm. The mean value at the posterior lip was 1.56 cm, ranging from 0.8 cm to 2.0 cm. This study showed that the actual positions of ligatures after cerclage operations varied very much. Unsatisfying position can be an explanation why some preterm deliveries can not be prevented. Therefore it is recommended to control the position of the cerclage ligation postoperatively using transvaginal sonography.