Characteristics of Fetal Heart Rate Tracings Prior to Uterine Rupture

Abstract

A worrisome fetal heart rate (FHR) tracing with variable decelerations is considered to be the commonest way in which uterine rupture presents. Late decelerations, bradycardia, or an undetectable heartbeat may ensue. Signs such as abdominal pain, vaginal bleeding, hypovolemia and shock, if they occur at all, are noted later in the course. This study attempted to identify the particular FHR patterns that develop within 2 hours before uterine rupture. Rupture was defined as a complete separation of the wall of the pregnant uterus, with or without fetal expulsion, which endangers the life of the mother and/or fetus. Asymptomatic dehiscence of a uterine scar was rejected, and all 11 eligible patients were at 28 weeks' or more gestation. The incidence of uterine rupture was 0.03%. Four patients lacked a uterine scar, whereas seven had a history of cesarean delivery. There were surgical or postoperative complications in 7 of 11 cases (64%), the commonest being infection and bleeding necessitating transfusion. Two of the patients with excessive bleeding required hysterectomy. Two of the three infected patients had postpartum endometritis, and one had pelvic cellulitis. One patient developed acute tubular necrosis and adult respiratory distress syndrome. None of the women died. All but one of the eight available FHR monitor strips (87.5%) exhibited recurrent late decelerations, and half showed bradycardia just before uterine rupture. Fetal bradycardia was consistently preceded by recurrent late decelerations. One fetus displayed prolonged decelerations, and one, fetal tachycardia preceding bradycardia. Only two tracings revealed variable decelerations. These findings, though based on a small sample, suggest that recurrent late FHR decelerations rather than variable decelerations may be a reliable early sign of impending uterine rupture.