Nicole M. Delorio
EPIDEMIOLOGY
Trauma is the leading cause of nonobstetric morbidity and mortality in pregnant women.
Motor vehicle crash is the most common mechanism of blunt abdominal trauma in pregnant patients, followed by falls and assault.
A significant percentage of trauma in pregnancy results from intimate partner violence.
PATHOPHYSIOLOGY
Abruption may be seen in patients with only minor abdominal trauma.
Physiologic changes of pregnancy make determination of injury severity problematic.
Heart rate increases 10 to 20 beats per minute in the second trimester, while systolic and diastolic blood pressures drop 10 to 15 mm Hg.
Pregnant patients exhibit a physiologic anemia due to a disproportionate increase in blood volume (up to 45%) compared to red cell mass.
Tachycardia, hypotension, and anemia may be due to blood loss or simply normal physiologic changes.
Due to the hypervolemic state, a patient may lose 30% to 35% of her blood volume before manifesting signs of shock.
CLINICAL FEATURES
The uterus is shielded by the bony pelvis until 12 weeks’ gestation. At 20 weeks, it reaches the level of the umbilicus and blood flow increases, making severe maternal hemorrhage from uterine trauma more likely.
The uterus can compress the inferior vena cava when the patient is supine, leading to the “supine hypotension syndrome.”
Decreased intestinal motility is associated with gastroesophageal reflux, predisposing the patient to vomiting and aspiration.
The bladder moves into the abdomen in the third trimester, increasing its susceptibility to injury.
Fetal injuries are more likely to be seen in the third trimester, often associated with pelvic fractures or penetrating trauma in the mother.
Uterine rupture is rare, but is associated with a fetal mortality rate of close to 100%.
More common complications of trauma include pre-term labor and abruptio placentae.
Maternal death is the most common cause of fetal death.
Abruptio placentae is also a common cause of fetal death, with a 50% to 80% mortality rate.
Abruption presents with abdominal pain, vaginal bleeding, uterine contractions, and signs of disseminated intravascular coagulation.
Fetal-maternal hemorrhage must be considered in cases of significant trauma and may result in Rh-isoimmunization of Rh-negative women.
DIAGNOSIS AND DIFFERENTIAL
Maternal stability and survival offer the best chance for fetal well being, so do not withhold critical interventions or diagnostic procedures out of concern for potential adverse effects on the fetus.
In addition to the standard trauma evaluation, direct special attention to the gravid abdomen, looking for evidence of injury, tenderness, or uterine contractions.
If abdominal or pelvic trauma is suspected, perform a sterile speculum examination, looking 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.
Shield the uterus from ionizing radiation when possible, and limit radiographs to those that will significantly impact the patient’s care.
Adverse fetal effects from ionizing radiation are negligible with doses <5 rad, which is an exposure far greater than that received from most trauma radiographs.
Abdominal and pelvic computed tomography (CT) scanning, pelvic angiography, and pelvic fluoroscopy result in the highest doses of radiation to the fetus.
Radiation exposure may be decreased by reducing the number of CT cuts obtained.
Bedside ultrasonography is a highly sensitive and specific radiation-free abdominal imaging alternative. In addition to assessing for free intraperitoneal fluid, ultrasonography can also identify fetal heart rate, gestational age, fetal activity or demise, placental location, and amniotic fluid volume. Ultrasound may miss uterine rupture, however.
MRI has not been associated with adverse fetal outcomes.
Diagnostic peritoneal lavage remains a valid modality for evaluating the pregnant abdominal trauma patient, but has been replaced primarily by ultrasound. An open supraumbilical technique should be used.
Auscultation of fetal heart tones for determining fetal viability and identifying fetal distress should be performed early in the evaluation; a normal rate is 120 to 160 beats per minute.
Fetal bradycardia is most likely to be caused from 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 all patients beyond 20 weeks’ gestation. A minimum of 4 to 6 hours is the generally accepted initial period of monitoring, which should be extended up to 24 hours in the case of documented uterine irritability. This should be performed even in those women who do not have an obvious abdominal injury.
Fetal tachycardia, lack of beat-to-beat or long-term variability, or late decelerations on tocodynamometry signify fetal distress and may be indications for emergent cesarean section if the pregnancy is beyond the viable gestational age.
EMERGENCY DEPARTMENT CARE AND DISPOSITION
As is the case with all trauma patients, initial priorities are the ABCs of resuscitation directed to the mother. Coordinate care with surgical and obstetric consultants.
Provide all pregnant trauma patients supplemental oxygen.
Initiate large-bore, peripheral IV lines with crystalloid infusions.
Avoid placement of IV lines in the femoral region and lower extremity if possible due to compression of the inferior vena cava by the uterus and possible pooling in the pelvic veins.
For patients beyond 20 weeks’ gestation who must remain supine, a wedge may be placed under the right hip, tilting the patient 30 degrees to the left, thus reducing the likelihood of supine hypotension syndrome. Otherwise, keep the patient in a left lateral decubitus position whenever possible.
Perform early gastric intubation to reduce the risk of aspiration.
Vasopressors can have deleterious effects on uterine perfusion and should be avoided.
Administer tetanus prophylaxis when indicated since it is not contraindicated in pregnancy.
Administer Rho-D immune globulin to all non-sensitized Rh-negative pregnant patients following abdominal trauma.
Tocolytics have a variety of side effects, including fetal and maternal tachycardia. Only administer them in consultation with an obstetrician.
Indications for emergent laparotomy in the pregnant patient remain the same as in the nonpregnant patient.
The decision to admit or discharge a pregnant trauma patient is based on the nature and severity of the presenting injuries and is often made after consultation with surgical and obstetric consultants.
Admit patients who display evidence of fetal distress or increased uterine irritability during initial observation.
Instruct patients who are discharged to seek medical attention immediately if they develop abdominal pain or cramps, vaginal bleeding, leakage of fluid, or perception of decreased fetal activity.
For further reading in Tintinalli’s Emergency Medicine: A Comprehensive Study Guide, 7th ed., see Chapter 253, “Trauma in Pregnancy,” by Nicole M. Delorio.