Predicting incomplete uterine rupture with vaginal sonography during the late second trimester in women with prior cesarean

Objective: To evaluate the usefulness of serial transvaginal ultrasonograph ic measurement of the thickness of the lower uterine segment in the late se cond trimester for predicting the risk of intrapartum incomplete uterine ru pture in women with previous cesarean delivery. Methods: Serial transvaginal ultrasonography with full bladder was performe d in 374 women without previous cesarean delivery (control group) and 348 w omen with previous cesarean delivery (cesarean group) from 19 to 39 weeks' gestation. The thickness of the lower uterine segment was measured in the l ongitudinal plane of the cervical canal. Results: The thickness of the lower uterine segment decreased from 6.7 +/- 2.4 mm (mean +/- standard deviation [SD]) at 19 weeks' gestation to 3.0 +/- 0.7 mm at 39 weeks' gestation in the control group, but the thickness was more than 2.0 mm throughout this period in each control subject. In the ces arean group, the thickness decreased from 6.8 +/- 2.3 mm at 19 weeks' to 2. 1 +/- 0.7 mm at 39 weeks' gestation and was significantly thinner than that of the control group after 27 weeks' gestation (P < .05). Eleven of 12 wom en (91%) with lower uterine segment less than the mean control - 1 SD in th e late second trimester had a very thin lower uterine segment at cesarean d elivery with fetal hair being visible through the amniotic membrane, ie, in complete uterine rupture. In 17 of 23 women (74%) with lower uterine segmen t less than 2.0 mm in thickness within 1 week (4 +/- 3 days) before repeat cesarean delivery, intrapartum incomplete uterine rupture developed. Conclusion: Transvaginal ultrasonography is useful for measurement of the u terine wall after previous cesarean delivery. (C) 2000 by The American Coll ege of Obstetricians and Gynecologists.