Chapter 159. Trauma in Pregnancy

Trauma is the leading cause of nonobstetric morbidity and mortality in pregnant women. Fetal survival is highly dependent on stabilization of the mother.

Physiologic changes of pregnancy make determination of severity of injury problematic. Heart rate increases 10 to 20 beats/min in the second trimester while systolic and diastolic blood pressures drop 10 to 15 mm Hg. Blood volume can increase by 45%, but red cell mass increases to a lesser extent, leading to a physiologic anemia of pregnancy. It may be difficult to determine whether tachycardia, hypotension, or anemia is due to blood loss or normal physiologic changes. Due to the hypervolemic state, the patient may lose 30% to 35% of her blood volume before manifesting signs of shock. Pulmonary changes in pregnancy include elevation of the diaphragm and decreases in residual volume and function residual capacity. Tidal volume increases, resulting in hyperventilation with associated respiratory alkalosis. Renal compensation causes the serum pH to remain unchanged.

Anatomic changes with pregnancy affect the types of injuries seen in the mother. After week 12 of gestation, the enlarging uterus emerges from the pelvis and by 20 weeks reaches the level of the umbilicus. Uterine blood flow increases, making severe maternal hemorrhage from uterine trauma more likely. The uterus also can compress the inferior vena cava when the patient is supine, leading to the “supine hypotension syndrome.” As pregnancy progresses, the small intestines are pushed cephalad, increasing their likelihood of injury in penetrating trauma to the upper abdomen. Decreased intestinal motility is associated with gastroesophageal reflux, thus predisposing the patient to vomiting and aspiration. The bladder moves into the abdomen in the third trimester, thereby increasing its susceptibility to injury. Splenic injury remains the most common cause of abdominal hemorrhage in the pregnant trauma patient.

Abdominal trauma affects the fetus and the mother. Fetal injuries are more likely to be seen in the third trimester, often associated with pelvic fractures or penetrating trauma. Uterine rupture is rare but is associated with a very high fetal mortality rate. More common complications of trauma include preterm labor and abruptio placentae. Second only to maternal death, abruptio placentae is a common cause of fetal death. Classically, the mother will demonstrate abdominal pain, vaginal bleeding, uterine contractions, and signs of disseminated intravascular coagulation. Fetal–maternal hemorrhage occurs in more than 30% of cases of significant trauma and may result in rhesus (Rh) isoimmunization of Rh-negative women.

Because maternal stability and survival offer the best chance for fetal well-being, no critical interventions or diagnostic procedures are withheld out of concern for potential adverse effects to the fetus. The initial sequence of trauma resuscitation is unchanged. Direct special attention to the gravid abdomen, examining for evidence of injury, tenderness, or uterine contractions. If abdominal or pelvic trauma is suspected, perform a sterile pelvic examination to assess for genital trauma, vaginal bleeding, or ruptured amniotic membranes. Fluid with a pH of 7 in the vaginal canal suggests amniotic rupture, as does a branch-like pattern, or “ferning,” on drying of vaginal fluid on a microscope slide.

Initial laboratory studies include a complete blood count, blood type, Rh status, and coagulation studies including fibrin split products and fibrinogen to determine the presence of disseminated intravascular coagulation. Order radiographs based on fundamental principles of trauma management. However, shield the uterus when possible and limit radiographs to those that will significantly affect the patient's care. Adverse fetal effects from radiation are negligible from doses lower than 5 rad, which is an exposure far greater than that received from most plain radiographs. Radiation exposure from CT may be decreased by reducing the number of imaging cuts. Bedside ultrasonography is a highly sensitive, specific, and radiation-free alternative for imaging the abdomen. In addition to evaluating fetal heart rate, ultrasonography can assess gestational age, fetal activity or demise, placental location, and amniotic fluid volume. MRI has not been associated with adverse fetal outcomes. Diagnostic peritoneal lavage remains a valid modality for evaluating the pregnant abdominal trauma patient, though it has largely been replaced by ultrasonography. If it is indicated, use the open supraumbilical technique.

Auscultate fetal heart tones to determine fetal viability and identify fetal distress early in the evaluation. A Doppler stethoscope or ultrasound facilitates this assessment. A normal fetal heart rate is in the range of 120 to 160 beats/min. Fetal bradycardia is most likely a result of hypoxia due to maternal hypotension, respiratory compromise, or placental abruption. Fetal tachycardia is most likely due to hypoxia or hypovolemia. In the setting of blunt abdominal trauma, external fetal monitoring is indicated for at least 4 to 6 hours for all patients beyond week 20 of gestation. 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 section if beyond the viable gestational age.

As is the case of all trauma patients, initial priorities are the primary and secondary surveys directed at the pregnant trauma patient. Coordinate care with surgical and obstetric consultants.

1. Aggressive maternal resuscitation is the best fetal resuscitation.

2. Initiate supplemental oxygen and crystalloid infusions. For patients beyond week 20 of gestation who must remain supine, place a wedge under the right hip, tilting the patient 30° to the left, thus reducing the likelihood of supine hypotension syndrome. Otherwise, keep the patient in a left lateral decubitus position.

3. Perform early gastric intubation to reduce the risk of aspiration.

4. Avoid vasopressors if possible as they can have deleterious effects on uterine perfusion.

5. Administer tetanus prophylaxis when indicated.

6. Consider Rho (D) immunoglobulin 300 micrograms IM for all nonsensitized Rh-negative pregnant patients after abdominal trauma.

7. Institute cardiotocodynamometry as soon as possible to monitor for fetal distress and uterine contractions.

8. Tocolytics have a variety of side effects, including fetal and maternal tachycardia. Administer only in consultation with an obstetrician.

9. Indications for emergent laparotomy in the pregnant patient remain the same as those in the nonpregnant patient.

10. The decision to admit or discharge a pregnant trauma patient is first based on the nature and severity of the presenting injuries. Admit patients who display evidence of fetal distress or increased uterine irritability during initial observation.

11. Instruct discharged patients to seek medical attention immediately if they develop abdominal pain or cramps, vaginal bleeding, leakage of fluid, or perception of decreased fetal activity.