Digital examination of the cervix has traditionally been the "gold standard" for cervical assessment. However, it can be subject to inter- as well as intra-observer variation. The usefulness of transvaginal ultrasonography for cervical assessment is examined in this study. Although differences between measurements of transvaginal ultrasonography and digital examinations were observed, transvaginal ultrasonography appears to be a potentially useful and reproducible technique for assessing cervical changes in pregnancy and for prediction of onset of labor.