- To determine changes in fetal heart rate (FHR) and uterine patterns preceding complete uterine rupture. FHR and uterine patterns of 50 women with uterine rupture were compared with 601 tracings of controls without scarred uteri. Tracings were interpreted using the National Institute of Child Health and Human Development Research Planning Workshop guidelines. Interobserver and intraobserver agreements of FHR and uterine tracings in the uterine rupture group were excellent (kappa of .96 for both variables). Comparing tracing patterns during the first stage, higher rates of severe fetal bradycardia (4.0% vs. 1.0%, P = .064), fetal tachycardia (8.0% vs. 2.3%, P = .042), reduced baseline variability (24.0% vs. 12.5%, P = .021), uterine tachysystole (10.0% vs. 0.8%, P < .001) and disappearance of contractions (6.0% vs. 0, P < .001) were noted among patients with uterine rupture as compared to the controls. During the second stage of labor, patients with uterine rupture had significantly higher rates of reduced baseline variability (47.8% vs. 7.7%, P < .001), severe variable decelerations (26.1% vs. 6.4%, P = .004), uterine tachysystole (22.0% vs. 0.5%, P < .001) and disappearance of contractions (13.0% vs. 0, P < .001). Using a backward, stepwise multiple logistic regression model, severe fetal bradycardia (OR = 8.2, 95% CI 2.2-31.0, P = .002) and uterine tachysystole (OR = should alert the 8.0, 95% CI 1.7-37.9, P = .008) were found to be independent patterns preceding uterine rupture during the first stage of labor. Likewise, during the second stage, reduced baseline variability (OR = 4.2, 95% CI 1.4-12.3, P = .009) and uterine tachysystole (OR = 42.3, 95% CI 10.6-168.3, P < .001) were independently associated with uterine rupture in another multivariable analysis. Abnormal monitor patterns among women presenting with risk factors for uterine rupture, specifically uterine tachysystole, reduced baseline variability and severe bradycardia, should act as warning signs to the obstetrician.