Epidemiology

Domestic violence is the most common cause of trauma during pregnancy,^3–6 affecting 11.1% of pregnant women,⁷ with a homicide rate of 2.9 per 100,000 live births.⁸ Other relatively common mechanisms of injury include motor vehicle crashes and falls (Table 4.1).^8–11

Anatomical Changes in Pregnancy

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  1st trimester: Uterus is small, thick-walled, confined to bony pelvis.

  
  
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  2nd trimester: Uterus rises out of pelvis and fills with amniotic fluid which protects the fetus, but may lead to post-trauma embolism or disseminated intravascular coagulation.¹²

  
  
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  3rd trimester: Uterus fully enlarges and is thin-walled. This places it at risk for injury from abdominal trauma; however, it displaces the diaphragm and bowel cephalad, protecting against penetrating visceral injuries (Figure 4.1).¹³

  
  
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  Throughout pregnancy, the pelvic vasculature dilates, and pelvic injuries may lead to exsanguination.¹⁴ Rapid drops in maternal intravascular volume can lead to fetal hypoxia, with a potentially minimal impact on maternal vital signs.¹⁵

Figure 4.1 Uterine anatomy during pregnancy

(image from: https://commons.wikimedia.org/wiki/File:2917_Size_of_Uterus_Throughout_Pregnancy-02.jpg)

Physiologic Changes in Pregnancy

There are a myriad of physiologic changes in pregnancy with important implications for trauma management (Table 4.2).^16–21

Overview of Initial Evaluation and Management

As with all trauma patients, the resuscitation of pregnant trauma patients should start with the primary survey. This includes assessments of the patient’s airway, breathing, circulation, disability (neurologic status), and complete exposure of the patient. The unique anatomy and physiology of pregnancy have important implications for each step of the primary survey.²²

Breathing

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  Recognize that a “normal” PaCO₂ of 35–40 mm Hg may portend impending respiratory failure in pregnant women who often have lower baseline PaCO₂ due to hyperventilation.

  
  
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  Mechanical ventilation settings should target PaCO₂ appropriate for the patient’s stage of pregnancy: approximately 30 mm Hg in late pregnancy.²⁷

  
  
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  Given the superior displacement of the diaphragm (Figure 4.2), some authors recommend chest tube thoracostomy placement in the third or fourth intercostal space rather than the fifth intercostal space, commonly used in non-pregnant patients.^{6, 28}

Figure 4.2 Images showing superior displacement of intestine by enlarged uterus intraoperatively (A) and on CT scan (B)

(reproduced with permission from Color Atlas of Emergency Trauma, Second Edition)

Circulation

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  Due to the intravascular volume expansion of pregnancy, women may lose up to 1,500 mL of blood before showing signs or symptoms of hypovolemia.²⁰

  
  
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  Guidelines advise against vasopressors given the risk of diminishing uterine blood flow.²⁴

  
  
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  Patients with hypotension should undergo 30–45°+ left lateral tilt to displace the uterus off the inferior vena cava; studies using magnetic resonance imaging and computer modeling suggest that less tilt yields inadequate decompression (Figure 4.3).^{29, 30}

Figure 4.3 Compression of IVC by enlarged uterus on CT scan (highlighted in circle)

(reproduced with permission from Color Atlas of Emergency Trauma, Second Edition)

Cardiopulmonary Resuscitation

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  Cardiopulmonary resuscitation via chest compression is thought to be less effective in pregnant patients due to aortocaval compression by the uterus.³¹

  
  
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  Peri-mortem cesarean section may improve outcomes for the mother and fetus alike by alleviating this compression.³²

  
  
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  The mother may hemodynamically benefit from this procedure even if the fetus is non-viable.³¹

  
  
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  While data are limited, they suggest optimization of maternal and fetal outcomes when performing peri-mortem cesarean section within 4 minutes of cardiac arrest (Table 4.3).^{31, 32}

Peri-Mortem Cesarean Section Procedure

1. 
   

   1. Sterilization by brief application of betadine to the incision site is appropriate, but should not come at the expense of rapid initiation of the procedure (Figure 4.4).

   
   
2. 
   

   2. Use a No. 10 scalpel to make a midline vertical incision through the abdominal wall spanning from the umbilicus to the symphysis pubis.

   
   
3. 
   

   3. Expose the uterus, ideally with assistants using retractors to draw the abdominal wound edges laterally and reflect the bladder inferiorly.

   
   
4. 
   

   4. Make a 5 cm vertical midline incision into the uterus, taking care to avoid fetal injury; stop incision upon achieving amniotic fluid return or visualization of the internal aspect of the uterine cavity.

   
   
5. 
   

   5. Insert index finger into incision to pull uterine wall away from the fetus and use bandage scissors to extend incision superiorly to the uterine fundus.

   
   
6. 
   

   6. Deliver the infant ideally by controlling the head; alternatively, if the head is inaccessible, deliver by grasping the infant’s feet.

   
   
7. 
   

   7. Immediately suction the infant’s nose and mouth, then clamp and cut the cord.

Figure 4.4 Penetrating abdominal and chest trauma in a blatantly gravid patient (A) that resulted in C-section delivery of the term infant (B). This resulted in neonatal resuscitation of the infant (C) but ultimately mother and child survived

(reproduced with permission from Color Atlas of Emergency Trauma, Second Edition)

Secondary Survey

Following the primary survey comes the secondary survey. This comprises a complete history and physical examination from head to toe. Unique considerations in pregnant women include:

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  Respiratory distress in absence of traumatic findings may reflect pulmonary edema due to pre-eclampsia³³ or amniotic fluid embolism.³⁴

  
  
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  Assess fundal height as a measure of gestational age and, hence, fetal viability.

  
  
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  The distance between the symphysis pubis and the uterine fundus in centimeters is a reasonable approximation of the weeks of gestation; approximately 24 cm distance suggests fetal viability.³⁵

  
  
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  Carefully assess the abdomen for trauma and tenderness; by acting as a barrier between the abdominal wall the peritoneum, the gravid uterus may theoretically mask peritonitis.

  
  
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  Vaginal examination to assess for bleeding, amniotic fluid (confirm by Nitrazine paper color change from yellow to blue), and cervical dilation or effacement.

  
  
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  A constellation of vaginal bleeding, abdominal pain, contractions, and uterine rigidity are suggestive of placental abruption or uterine rupture and require immediate obstetrics consultation. Ultrasonography is useful if positive, but will be negative for many abruptions.³⁶

  
  
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  Signs of pre-eclampsia, including hypertension, pulmonary edema, neurologic findings, and visual deficits.³³

  
  
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  Signs of eclampsia, namely neurologic examination, with recognition that seizures in a pregnant patient with head trauma may represent either intracranial hemorrhage or eclampsia.

Fetal Assessment

Pregnant women must also undergo evaluation of the pregnancy via fetal and uterine monitoring.^{24, 37} Fetal assessment depends upon whether the fetus has reached viability. The literature generally suggests that fetal viability is ≥24 weeks gestation, though this cut-off is highly situation and setting specific, and may be as low as 22–23 weeks.^38–40 In situations of ambiguity regarding gestational dates, some authors advocate considering as viable any fetus at approximately 20 weeks gestation or greater with the uterine fundus at the level of the umbilicus.⁴¹

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  Prior to viability, fetal assessment should include measurement of fetal heart rate by Doppler or ultrasound; normal is 120–160 beats per minute.

  
  
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  Past the date of viability, pregnant women sustaining even ostensibly minor abdominal trauma should undergo at least 4 hours of continuous monitoring of fetal heart rate and uterine contractions, ideally under the care of an obstetrician (Figure 4.5).⁴²

  
  
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  Signs of impending maternal or fetal decompensation include abnormal fetal heart rate, repetitive late or variable decelerations, absence of fetal heart rate variability, and frequent uterine contractions.⁴³

  
  
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  Any signs of ruptured membranes or impending labor in the setting of fetal viability mandates obstetrics consultation for further monitoring and management.

Figure 4.5 Cardiotocographic monitoring of fetal heart rate variability and uterine contractions

(reproduced with permission from Color Atlas of Emergency Trauma, Second Edition)

Ultrasound Examination

Ultrasound provides an increasingly available non-radiating imaging modality which may supplement the physical examination of the pregnant woman and her fetus. Potential applications include:

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  A focused assessment with sonography for trauma (FAST) examination remains the cornerstone of diagnostic ultrasonography in trauma, but has imperfect sensitivity for intra-peritoneal bleeding (Figure 4.6).⁴⁴

  
  
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  It is sometimes possible to identify signs of placental abruption such as sub-chorionic hemorrhage, though ultrasound has poor sensitivity for this disease process.³⁶

  
  
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  The literature reports cases of detection of fetal injuries such as intracranial hematomas and skull fractures in utero via ultrasound, though absence of ultrasound findings should again not be considered to definitively rule out injuries.^{45, 46}

  
  
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  Evaluation of fetal heart rate when this remains undetectable by other mechanisms. The provider places an M-mode cursor beam over the fetal heart, then determines the heart rate by measuring the distance between heart beats.

Figure 4.6 View of positive FAST in Morrison’s Pouch

(reproduced with permission from Color Atlas of Emergency Trauma, Second Edition)

Diagnostic Evaluation

As with all trauma patients, providers should order those laboratory and imaging tests which, based upon clinical suspicion, they believe are likely to change management. Considerations specific to pregnant trauma patients include:

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  Providers should not refrain from ordering diagnostic imaging modalities involving radiation based upon their clinical suspicion for traumatic disease, as the radiation exposure to the fetus is minimal and fetal survival depends upon maternal well-being.⁴⁷

  
  
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  All pregnant trauma patients should undergo Rh(D) testing.

  
  
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  Women who are Rh(D) negative should undergo Kleihauer-Betke testing to quantify fetomaternal hemorrhage and so guide dosing for Rh(D) immune globulin to prevent isoimmunization in the event the fetus is Rh(D) positive.⁴⁸

  
  
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  Laboratory studies in conjunction with blood pressure measurements to investigate pre-eclampsia including urinalysis, complete blood count, renal function panel, and liver function tests (Table 4.4).³³

Therapeutic Considerations

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  In consultation with obstetrics, consider administration of corticosteroids to pregnant women at increased risk for preterm birth with gestations of viable age but prior to 34/35 weeks to optimize fetal lung development (betamethasone 12 mg intramuscular vs. dexamethasone 6 mg intramuscular).⁴⁹

  
  
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  Any Rh(D) negative woman experiencing significant trauma should receive 300 µg of Rh(D) immune globulin intravenous⁵⁰; Kleihauer–Betke testing should guide whether higher doses are necessary to prevent isoimmunization.⁴⁸

  
  
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  There is no contraindication to tetanus toxoid in pregnancy, and pregnant trauma patients meeting standard indications should receive this vaccination.⁵¹

  
  
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  Providers should have a high index of suspicion for placental abruption, as it remains the most common complication associated with trauma in pregnancy. Incidence has been reported as high as 5% in minor traumatic injuries and up to 65% with more severe mechanisms (Figure 4.7).⁵²

Figure 4.7 CT representation of placental abruption (A). Placental abruption specimen obtained after emergency C-section

(reproduced with permission from Color Atlas of Emergency Trauma, Second Edition)

Other Considerations

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  Given the high proportion of pregnant trauma patient sustained injuries due to intimate partner violence, be sure to screen these patients for domestic violence in a private setting without partners present.⁵³

  
  
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  Have a low threshold for transfer to tertiary care centers, as there are correlations between even seemingly isolated trauma (e.g., single extremity fractures) and adverse maternal and fetal outcomes.^{54, 55}

Pitfalls in ED Evaluation and Management

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  Assuming a PaCO₂ of 35–40 mm Hg is normal; these levels may portend impending respiratory failure in pregnant women who generally have a lower baseline PaCO₂ due to hyperventilation, particularly in the later stages of pregnancy.

  
  
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  Relying solely upon maternal vital signs and symptoms to guide volume resuscitation; given the intravascular volume expansion of pregnancy, women may lose up to 1,500 mL of blood before showing signs or symptoms of hypovolemia.

  
  
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  Applying less than 30° of left lateral tilt in hypotensive pregnant women; tilt less than this amount may not yield clinically significant decompression of the inferior vena cava.

  
  
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  Delayed initiation of peri-mortem cesarean section; maternal and fetal outcomes are optimized by performing this procedure within 4 minutes of cardiac arrest.

  
  
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  Failure to consider pre-eclampsia in pregnant women seizing after head trauma.

  
  
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  Relying upon ultrasonography to rule out placental abruption.

  
  
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  Refraining from diagnostic imaging modalities entailing ionizing radiation given concerns for fetal radiation exposure at the expense of potentially missing maternal injuries.

  
  
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  Failure to obtain Kleihauer-Betke testing to guide Rh(D) immune globulin dosing in Rh(D) negative women status post-significant trauma, placing them at high risk for fetomaternal hemorrhage.

  
  
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  Failing to screen pregnant trauma patients for domestic violence in a private setting without partners present.