A rapid assessment of fetal condition should be initiated with auscultation of fetal heart tones to determine fetal viability and identify fetal distress. Assessment of fetal heart tones may be augmented by use of a Doppler stethoscope or ultrasound. It has been suggested that fetal viability in the setting of trauma is directly related to the presence or absence of fetal heart tones on presentation, and that if these are confirmed absent, then the remainder of treatment efforts be directed solely at maternal resuscitation.3 Normal fetal heart rates are in the range of 120 to 160 beats per minute. The most likely cause of fetal bradycardia is acute hypoxia. In acute injuries, maternal hypotension, hypothermia, respiratory compromise, or placental abruption are likely etiologies. Similarly, in the setting of acute trauma, the finding of fetal tachycardia may also represent a hypoxic or hypovolemic state.
The use of bedside ultrasound has become an increasingly valuable adjunct to initial trauma assessment and management. Portable ultrasound has been shown to be rapid, noninvasive, and facilitates serial examinations.14 In cases of trauma during pregnancy, ultrasonography may also be of particular value in the evaluation of general fetal condition. Fetal size and estimated gestational age, the presence of fetal heart motion, fetal activity or demise, placental location, and amniotic fluid volume can be assessed.4!5 The efficacy of ultrasound, however, for the diagnosis of specific trauma-related injuries remains unproven. Several recent reports have suggested the relative inability of ultrasound to diagnose uterine rupture or fetal-placental injuries, and its sensitivity is insufficient to exclude the diagnosis of placental abruption.12!5 The intraabdominal anatomic distortions of late third-trimester pregnancy may further limit the diagnostic capability of ultrasound in acute trauma.
In the management of blunt trauma during pregnancy, external fetal monitoring is indicated for gestational age estimated beyond 20 weeks. The initiation of fetal tocodynamometry is recommended at the earliest possible stage of evaluation following maternal stabilization, preferably in the emergency department. Fetal monitoring is utilized to assess both uterine contractile activity as well as fetal heart rate. Beyond the viable gestational age of 23 weeks, the presence of fetal tachycardia, lack of beat-to-beat or long-term variability, or late decelerations on tocodynamometry are diagnostic of fetal distress and may be indications for emergent cesarean delivery.
The identification of frequent uterine activity on external fetal monitoring has been shown to be a sensitive predictor of abruptio placentae beyond 20 weeks of gestation. In a major prospective study, no cases of abruptio placentae were identified unless more than 8 contractions per hour were found during the first 4 h of tocodynamometry.1 A minimum of 4 h of external tocodynamometric monitoring appears to be predictive of immediate adverse pregnancy outcomes and is indicated for all pregnant patients evaluated for trauma. Patients demonstrating 3 to 7 contractions per hour of persistent uterine irritability should have tocodynamometry extended to a minimum of 24 h. They may subsequently be safely discharged if uterine contractions abate and other reasons for further evaluation do not exist. Patients with fewer than 3 contractions per hour during an initial 4-h observation period can be safely discharged. This approach has been shown to have the same pregnancy outcomes among discharged patients when compared with uninjured controls.
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