- Objective This study was undertaken to determine uterine and fetal heart rate (FHR) tracing patterns associated with clinically apparent uterine leiomyomas. Study design Uterine and FHR patterns of 44 women with diagnosed uterine leiomyomas were compared with 601 tracings of controls. Tracings were interpreted during the first stage of labor, using the National Institute of Child Health and Human Development Research Planning Workshop guidelines. Stratified analysis that used the Mantel-Haenszel technique was performed to control for confounders. Results Patients with leiomyomas had higher rates of uterine tachysystole as compared with those without leiomyomas (22.7% vs 1.3%; odds ratio [OR] = 21.8, 95% CI 7.4-65.6; P < .001). No significant differences were noted between the groups regarding FHR patterns. Higher rates'of prostaglandin induction and oxytocin augmentation were noted in the uterine leiomyomas group (6.8% vs 0.8%; P = .005 and 52.3% vs 10.5%; P < .001, respectively). However, controlling for prostaglandin induction and oxytocin augmentation, with the use of the Mantel-Haenszel procedure, did not change the significant association between uterine leiomyomas and tachysystole (weighted OR 12.5, 95% CI 6.2-75.1, and weighted OR 8.7, 95% CI 3.6-43.1, respectively). Conclusion Clinically apparent uterine leiomyomas, although not coupled with abnormal FHR patterns, are associated with higher rates of tachysystole.