Fetal heart rate changes associated with uterine rupture.

Abstract

To identify fetal heart rate characteristics of patients with uterine rupture compared with successful vaginal birth after cesarean (VBAC) controls. This is a case-control study. Obstetric records of patients at the University of Washington Medical Center and Swedish Medical Center were reviewed for cases of uterine rupture. Entry criteria included operative confirmation of the diagnosis, gestational age beyond 24 weeks, presence of one or more prior low transverse uterine incisions, and availability of fetal heart tracings. Each case was matched with 3 controls randomly selected from a pool of successful VBAC deliveries at the same institution within 1 year. Three blinded independent examiners then examined fetal heart tracings. Each tracing was rated for the presence of fetal tachycardia, mild or moderate variable decelerations, severe variable decelerations, late decelerations, prolonged decelerations, fetal bradycardia, and loss of uterine tone in both the first and second stages of labor separately. Of the 48 uterine ruptures identified, 36 met inclusion criteria. These were matched with 100 controls. Cases showed significantly increased rates of fetal bradycardia than controls in the first stage (P <.01) and second stage (P <.01). No significant differences were noted in rates of mild or severe variable decelerations, late decelerations, prolonged decelerations, fetal tachycardia, or loss of uterine tone. Fetal bradycardia in the first and second stage is the only finding to differentiate uterine ruptures from successful VBAC patients. II-2