Abstract: Changes of cervical ultrasonographic physical parameters and their association with outcome of cerclage have not been fully elucidated. This study aimed at evaluating association between ultrasonographic physical cervical shapes before and after McDonald cerclage with the length of pregnancy. Cervical length, width and funneling rate were assessed by transvaginal ultrasonography before and after the procedure. Mean pre-cerclage cervical length, width and funneling rate were 29.28±5.54, 19.92±10.30 mm and 12.90±18.87%, respectively. The mean post-cerclage cervical length, diameter and funneling rate were 31.68±4.21, 9.78±13.86 and 4.32±10.89%, respectively (p<0.001 for all pre- and post-cerclage changes). The mean post-cerclage duration of pregnancy was 19.78±5.94 weeks. There were significant direct correlations between the pre- and post-cerclage cervical lengths with pregnancy duration (r = 0.24, p = 0.04 and r = 0.44, p<0.001, respectively). There were significant indirect correlations between the pre- and post-cerclage funneling rate with pregnancy duration (r = -0.30, p = 0.01 and r = -0.20, p = 0.01, respectively). Similar correlations were not significant for the cervical widths. This study showed that the pre- and post-cerclage ultrasonographically determined cervical length and funneling are good predictors of pregnancy duration.