Key Abbreviations
100 cGy or 100 rads 1 Gray
Centigray cGy
Computerized tomography CT
Focused abdominal sonography for trauma FAST
Kleihauer-Betke test KB
Magnetic resonance imaging MRI
Motor vehicle crash MVC
Radiation absorbed dose rad
Incidence of Trauma in Pregnancy
Because of underreporting, the actual incidence of trauma during pregnancy is unknown. However, traumatic injury has been reported to complicate 6% to 8% of all pregnancies and is the leading cause of nonobstetric maternal death. Approximately 30,000 pregnant women in the United States sustain treatable injuries each year as a result of trauma.
Worldwide, trauma is responsible for at least 1 million deaths annually and is the leading cause of death in individuals under 40 years of age in the United States.
The risk of maternal death is related to injury severity. In a large California database study of women hospitalized for trauma between 1991 and 1997, El Kady and colleagues found that intraabdominal injuries are the most common type of injury leading to maternal death, and intracranial injury resulting from trauma was the second most common cause of maternal death.
In addition to risk for maternal morbidity and mortality, traumatic injuries can have significant fetal effects that include an increased risk for fetal death and other adverse outcomes. The incidence of spontaneous abortion (SAB), preterm birth, preterm premature rupture of membranes (PPROM), uterine rupture, cesarean delivery, placental abruption, and stillbirth are all increased.
A 3-year, 16-state fetal death certificate review calculated the rate of fetal death from maternal trauma at 2.3 per 100,000 live births, and placental abruption was the leading contributing factor. Based on a review of Pennsylvania fetal death certificates, it is estimated that motor vehicle crashes (MVCs) result in between 90 and 367 fetal deaths in the United States annually.
However, because of nonstandardized reporting of fetal death or injury resulting from maternal trauma, the exact magnitude of disease burden to the fetus from trauma is believed to be underestimated. Factors associated with an increased risk for traumatic injury during pregnancy include young maternal age, African-American or Hispanic ethnicity, domestic violence, lack of seatbelt use, and drug or alcohol use.
In 2002 in the United States, 4.1 injury-related hospitalizations of pregnant women occurred per 1000 deliveries; and of those hospitalizations, it was estimated that 1 in 3 pregnant women admitted to the hospital for trauma underwent delivery during that hospitalization. Alcohol may be involved in as many as 45% of MVCs that involve pregnant women, and the use of illicit substances has been implicated frequently in maternal trauma during pregnancy.
Traumatic injuries may be categorized according to type and include blunt trauma, penetrating trauma, fractures, and thermal injuries. An updated systematic review reported prevalence rates for the various mechanisms of trauma. MVCs had an estimated incidence of 207 per 100,000 live births, and the incidence of domestic violence (DV) or intimate partner violence (IPV) was 8307 per 100,000 live births compared with an incidence outside of pregnancy of 5239 per 100,000 women. Falls, burns, homicide, suicide, and toxic exposure are also major contributors to traumatic injury. Gunshot wounds and burns account for 4% and 1% of maternal trauma respectively. The most common obstetric complications following maternal trauma are those associated with blunt trauma and include abruptio placentae, preterm labor, and fetal loss.
Anatomic and Physiologic Changes of Pregnancy
The importance of maternal physiologic changes during pregnancy and an understanding of fetal physiology are critical to effective resuscitation of the injured pregnant woman. This is especially important relative to the maternal response to stress and hypovolemia in the setting of trauma. Fundamental differences exist in the physiologic responses as a result of pregnancy, and a working knowledge of these differences is important to trauma resuscitation.
Fetal Physiology
Several factors are important in determining the impact of a traumatic event on pregnancy outcome. These include gestational age, type and severity of trauma, and the extent of disruption of normal maternal and fetal physiology.
In the first week following conception, the nonimplanted embryo is relatively resistant to noxious stimuli. During the first trimester, the uterus resides relatively safely within the confines of the bony pelvis and has reached just above the pubic symphysis by 13 to 14 weeks’ gestation. As such, the uterus is protected to a large degree from direct trauma. At any gestational age after implantation, however, maternal hypovolemia may have a significant impact on the developing embryo/fetus. Pregnancy loss in the first trimester is not likely related to direct uterine injury but more so from physiologic cardiovascular changes that occur with maternal hypovolemia and associated hypotension, which results in hypoperfusion of the uterus and the developing fetus. Uterine blood flow is not autoregulated and is maximally dilated in the normal physiologic state. Maternal hypovolemia may result in vasoconstriction in vascular beds, including the uterine vessels. In experimental hypovolemic shock, pregnant sheep will decrease uterine blood flow at rates greater than would be expected with a decrease in maternal blood pressure alone. Even in the absence of uterine artery vasoconstriction, decreases in maternal blood pressure as a result of hypovolemia will result in decreased uterine blood flow. These phenomena underlie the importance of maintaining adequate maternal blood volume as an initial step in fetal resuscitation. The third-trimester fetus can adapt to decreased uterine blood flow and oxygen delivery by redistributing blood flow to the heart, brain, and adrenal glands. Furthermore, because fetal hemoglobin has a greater affinity for oxygen than adult hemoglobin, fetal oxygen consumption does not decrease until oxygen delivery is reduced by 50%.
The leading cause of blunt abdominal trauma in pregnancy is motor vehicle accidents . Penetrating trauma is typically the result of gunshot and stab injuries. Both blunt and penetrating trauma may result in rupture of the amniotic membranes. In the mid second trimester, rupture with oligohydramnios may result in pulmonary hypoplasia or orthopedic deformity. Injury to the placenta may precipitate placental abruption and lead to fetal anemia, hypoxemia, or hypovolemia. Maternal mortality risk with penetrating trauma is more favorable than with blunt trauma because nonreproductive viscera are provided some protection by the gravid uterus, which absorbs the projectile objects.
Maternal Anatomic and Physiologic Changes
Nearly every maternal organ system undergoes anatomic or physiologic changes during pregnancy. The description that follows emphasizes consideration of these changes that affect trauma management.
A major concern in the management of trauma victims is internal hemorrhage and hypovolemia. The sentinel findings on examination are vital sign abnormalities, typically hypotension and tachycardia. Consideration should be given to the normal decrease in systemic vascular resistance that results in a decrease in mean blood pressure of 10 to 15 mm Hg and an increase in pulse of 5 to 15 beats/min, particularly in the second trimester. These changes can be accentuated if the trauma victim is placed in the supine position (e.g., strapped to a long board to secure the cervical spine). The resultant potential decrease in venous return from the lower extremities can reduce central venous volume and result in a diminished cardiac output by as much as 30%. Simple manual displacement of the uterus to the left or placement of a rolled towel under the backboard while ensuring that the spine remains secure alleviates most of this effect.
Blood volume increases by a mean of 50% in the singleton gestation. This is usually maximal by 28 to 30 weeks’ gestation. Red blood cell mass increases to a lesser degree than does plasma volume, resulting in a slight decrease in hemoglobin concentration and a decrease in hematocrit. Iron-deficiency anemia is also common during pregnancy, and together with the normal dilution, hemoglobin concentrations may often be as low as 9 to 11 g/dL. These hematologic changes have two potential implications: anemia may be confused with active bleeding and hypovolemia, and blood volume estimates should be adjusted upward during fluid resuscitation.
Several major pregnancy-induced changes in the gastrointestinal tract are also important for trauma management. Compartmentalization of the bowel upward serves to protect it during lower abdominal trauma but increases the risk of injury when penetrating trauma to the upper abdomen occurs late in pregnancy. Complex injuries to the small bowel can be encountered with multiple entry and exit wounds as a result of its being crowded and compacted into the upper abdomen. Decreased gastric motility results in a prolonged gastric emptying time thereby increasing the risk of aspiration associated with general anesthesia. Rebound tenderness and guarding may be less apparent in later gestation because of stretching and attenuation of the abdominal musculature and peritoneum.
The dramatic increase in uterine blood flow, up to 600 mL/min, may result in rapid exsanguination in the event of an avulsion or injury to the uterine vasculature or rupture of the uterus. Retroperitoneal hemorrhage from remarkably hypertrophied pelvic vasculature is a common complication of pelvic fracture.
Blunt Trauma
Enlargement of the uterus makes it susceptible to direct abdominal trauma. Injury to the uterus (uterine laceration or rupture), its contents (abruptio placentae or direct fetal injury), or adjacent organs (bladder rupture) are more likely during pregnancy, especially in the second half of gestation. Although some of these complications are associated with more direct and violent trauma—for example, direct fetal injury or uterine rupture—some injuries, such as abruptio placentae, can occur following relatively minor trauma.
Blunt trauma to the maternal abdomen is an important cause of abruptio placentae. This is because blunt trauma exposes the gravid uterus to acceleration-deceleration forces that have a differential effect on the uterus and the attached placenta. By changing its shape, the myometrial tissue can stretch and adapt to these forces, but the placenta is relatively inelastic. This mismatch between myometrial and placental ability to stretch creates a shearing force at the uteroplacental interface that, if sufficient, can result in separation of the placenta from its myometrial attachments (i.e., placental abruption). Placental abruption leads to a compromise in fetal oxygen transfer and has the potential for fetal death depending on severity. Because amniotic fluid is noncompressible, impact against the uterine wall results in amniotic fluid displacement and uterine distension. As such, seemly minor or nonseverely injured pregnant women are at increased risk for placental abruption. Abruption may occur immediately after the abdominal impact or may be delayed for several hours after the trauma episode. Maternal trauma may also result in intramyometrial bleeding that leads to increased uterine contractile activity through activation of thrombin, lysosomal enzymes, cytokines, and prostaglandins. Severe blunt trauma may also lead to maternal splenic, hepatic, and retroperitoneal injuries that result in maternal hemorrhage and hemodynamic instability.
Motor Vehicle Crashes
A number of human factors are related to traffic-related injuries and fatalities in the United States. For many reasons, drivers have become more distracted while driving. According to the National Highway Transportation Safety Administration (NHTSA) report for 2012, a motor vehicle crash (MVC) occurs every 14 seconds, an injury every 14 seconds, and a death on average every 16 minutes in the United States. MVCs are the most common cause of trauma-associated fetal loss in the United States . The likelihood that an MVC will result in fetal loss is directly related to crash severity and to the severity of the maternal injury. For example, estimates based on case series would suggest that only about 1% of minor MVCs will result in abruptio placentae, whereas clinically evident abruption occurs in as many as 40% to 50% of cases of severe blunt maternal trauma. In addition, lack of seatbelt use has been found to be associated with fetal loss, particularly if the mother has experienced ejection from the vehicle and head trauma. However, even a nonsevere MVC without substantial maternal injury may result in placental abruption and fetal loss because of exposure to the shearing acceleration-deceleration forces described earlier.
Falls
Because pregnancy changes the center of gravity and results in postural instability, loss of balance is not uncommon, and the likelihood of a significant fall is increased. A retrospective study found that as many as a quarter of pregnant women experience a fall at some time during pregnancy. Like MVCs, falls expose the placenta to the shearing forces associated with blunt trauma. However, compared with MVCs, the likelihood that a fall may result in placental abruption and fetal death is low, accounting for only 3% of trauma-associated fetal deaths in one series . In a more recent prospective cohort study that involved 153 women who experienced falls during pregnancy, no instances of placental abruption were reported. Nonetheless, compared with pregnant women who did not experience a fall-related hospitalization during pregnancy, women hospitalized for falls remain at increased risk for adverse outcomes of pregnancy. One retrospective cohort study of 693 women hospitalized for falls during pregnancy, most of whom were in the third trimester, found that these women were at increased risk for preterm labor, placental abruption, cesarean delivery, “fetal distress,” and fetal hypoxia.
Domestic Violence and Intimate Partner Violence
Pregnant women are at increased risk to suffer violent assault compared with nonpregnant women. The period prevalence of intimate partner violence (IPV) during pregnancy has been reported to range from 6% to 22%, and up to 45% of pregnant women report a history of domestic abuse at some time during their lifetime. The rates of suicide and homicide in pregnancy have been reported as approximately 2.0 per 100,000 and 2.9 per 100,000 live births, respectively. Black women account for nearly half (44.6%) of pregnancy-related homicides but only 17.7% of live births, and 45.3% were associated with IPV. Victims of suicide were more likely to be older and white, and 54.3% of pregnancy-associated suicides involved IPV. Common methods of self-inflicted attempted suicide are drug overdose and poisoning with a corrosive substance. In one study, murder was the most frequent cause of death during pregnancy and in the subsequent year, and the majority of the perpetrators were found to be current or former intimate partners. This analysis of pregnancy-associated homicides found that intimate partner homicides were most likely to occur during the first 3 months of pregnancy. In a United States study, 5% of female homicide victims were pregnant. Although domestic violence occurs in all ethnic and socioeconomic groups, black and Native American women and women from households with lower incomes are at increased risk. Intentional trauma during pregnancy has a 2.7-fold risk (95% confidence interval [CI], 1.3 to 5.7) for preterm birth and a 5.3-fold risk (95% CI, 3.99 to 7.3) for low birthweight. According to a California database study of maternal discharge records between 1991 and 1999, assaults were significantly associated with uterine rupture and conferred significant risks for placental abruption and low birthweight, even if the victim was not delivered during the initial hospitalization.
Specific Injuries
Fractures
Fractures are the most common type of maternal injury to require hospitalization during pregnancy, and the lower extremities are the most common site of fractures that complicate pregnancy. Although pelvic fractures are less frequent than fractures of the extremities, pelvic fractures are most likely to result in adverse outcomes of pregnancy, including placental abruption and perinatal and infant mortality ( Fig. 26-1 ). Leggon and colleagues reported on a total of 101 pelvic or acetabular fractures in pregnant women, and the three most common reasons for injury were motor vehicle accidents (73%), falls (14%), and pedestrian struck by an automobile (13%). The overall fetal mortality rate in pelvic and acetabular fractures was 35% compared with 9% maternal mortality. Thus pelvic fractures are thought to be an independent risk factor for adverse fetal outcome. Pelvic fractures may also be associated with significant maternal hemorrhage and shock as a result of significant hypertrophy of the pelvic retroperitoneal vasculature and subsequent laceration of these vessels because of sharp bone fragments. Pelvic fractures may also be associated with bladder and urethral trauma. Pelvic fractures are not a contraindication to vaginal delivery unless the fracture results in obstruction of the birth canal or if the pelvic fracture is unstable; more than 80% of women who have sustained pelvic fractures can deliver vaginally.
Penetrating Trauma
Gunshot and stab wounds are the most frequent types of penetrating trauma during pregnancy. Penetrating trauma in a pregnant woman is less likely to result in death than penetrating trauma in a nonpregnant individual owing to the protective effect of the gravid uterus when penetrating wounds occur in the upper abdomen. However, penetrating trauma poses major risk for complex maternal bowel injury because of the compartmentalization of the bowel in the upper abdomen by the enlarged uterus. Gunshot wounds to the abdomen require exploratory surgery to determine the degree of abdominal viscera injury and debridement of damaged tissues. A stab wound in a pregnant woman should be managed the same as in a nonpregnant woman. Bowel injury with spillage of the intestinal contents increases the risk for peritonitis and pregnancy loss from infection. Penetrating trauma to the uterus is strongly associated with poor fetal outcome. Fetal death is dependent upon the degree of placental or umbilical cord disruption. The risk of fetal death has been reported to be as high as 71% after gunshot wounds and as high as 42% following stabbings.
Thermal Injuries (Burns)
Maternal and fetal prognosis after thermal injury is a reflection of the percentage of body surface involved . Minor burns that involve 10% or less of the body surface area are unlikely to result in maternal or fetal compromise and do not always require hospitalization. Significant burns of 50% or more of the body surface have been associated with high maternal and fetal mortality . In the past, delivery of the fetus was recommended in an attempt to improve maternal prognosis. More recent studies have suggested that maternal prognosis after severe thermal injury is not different between pregnant and nonpregnant individuals. However, because of maternal physiologic changes associated with pregnancy, a pregnant woman with a severe burn will require more aggressive fluid resuscitation than a nonpregnant individual . Major burns may result in maternal hypovolemia and cardiovascular instability in addition to sepsis, respiratory distress, renal failure, and liver failure. Because of the decreased colloid osmotic pressure and increased body surface area associated with pregnancy, pregnant individuals who sustain burns are at risk for increased fluid loss compared with nonpregnant individuals. Preterm labor may result from maternal hypovolemia, which can also result in decreased uteroplacental perfusion. Aggressive fluid resuscitation is critical to forestall this complication.
Individuals who suffer from major burns may also sustain inhalation injuries, which carry higher maternal mortality and fetal risk. In particular, carbon dioxide freely crosses the placenta and is highly bound by fetal hemoglobin, thus increasing the risk for fetal cardiac failure. Administration of oxygen to the mother is recommended to reduce the half-life of carboxy-hemoglobin.
Direct Fetal Injuries
Direct fetal injuries are uncommon because of the protection by the uterus and amniotic fluid. Fetal injury complicates fewer than 1% of pregnancies with blunt trauma but are most likely to occur with both direct and severe abdominal or pelvic impact and also in later pregnancy, when the fetal head is engaged in the maternal pelvis. Direct injury has been reported to result in rupture of the fetal spleen, fracture of the fetal skull, fetal intracranial hemorrhage, and cerebral edema. Near term the fetal head is in the maternal pelvis, thereby increasing the risk for fetal skull fracture and brain injury with maternal pelvic fractures. Blunt trauma due to violence can lead directly to fetal injury. These injuries have been reported to result in long-term developmental disabilities that result from vascular infarctions, global cerebral damage, and periventricular leukomalacia.
Pathophysiology of Fetal Loss Resulting From Maternal Trauma
Maternal hypotension and hypovolemia associated with trauma are important predictors of poor fetal outcome. Fetal loss may result from placental hypoperfusion due to maternal hemorrhagic shock. In the instance of severe blood loss that results from maternal trauma, maternal blood is redistributed away from the uterus via uterine artery vasoconstriction, thereby allowing continued perfusion of the heart and brain. Fetal mortality in the setting of maternal hemorrhagic shock has been estimated at 80%.
Predictors of Fetal Mortality
Abruptio placentae is by far the leading cause of fetal death in published series and accounts for between 50% and 70% of all fetal losses due to trauma. Placental abruption will complicate about 1% to 2% of cases of maternal trauma with low injury severity scores and up to 40% of severe maternal abdominal trauma. If a placental abruption occurs, the risk of fetal mortality has been reported to be as high as 50% to 80%. Maternal death has been reported as the next most frequent cause of fetal death after placental abruption, accounting for about 10% of losses. In a large California database study, gestational age at delivery was the strongest predictor of fetal, neonatal, or infant death. MVCs (82%) are the most frequent mechanism of injury leading to fetal death, followed by gunshot wounds (6%) and falls (3%). In particular, lack of seatbelt use is a substantial risk factor for poor fetal outcome, morbidity, and mortality.
Schiff and colleagues used the injury severity score to categorize the severity of maternal injuries. The risk for adverse maternal, fetal, and neonatal outcomes was greatest among the women with severe injuries but was also increased for women with mild injuries compared with uninjured controls. They found that injury severity scoring had limited predictive accuracy for placental abruption and fetal death and that even relatively minor injuries can result in these adverse fetal outcomes. Because minor injuries are much more common than severe injuries, they are responsible for 60% to 70% of fetal losses attributable to trauma, even though a severe injury is much more likely to result in fetal loss than a nonsevere injury.
Management Considerations
Initial Approach
The most important initial step in the management of the pregnant trauma victim is a thorough evaluation and stabilization for transport to a trauma center. This initial evaluation is typically provided by on-site emergency medical technicians (EMTs). Most EMT personnel are familiar with the designated trauma units in the community equipped to deal with cases of severe trauma. This is especially important for the pregnant trauma victim, for whom both maternal and fetal survival is a priority. The Centers for Disease Control and Prevention (CDC) has provided published guidelines for first responders and emergency medical personnel who provide care in the field to injured pregnant women. Guidelines for emergency medical personnel include displacing the uterus from the inferior vena cava by positioning the mother in the lateral decubitus position. During the initial evaluation, the spine immobilization board may be tilted leftward by 15 degrees by placing a 6-inch rolled towel under the long board to achieve the same result. The CDC panel recommended that if possible, women with a pregnancy of at least 20 weeks’ gestation be transported to a trauma center with access to obstetric care. If a pregnant trauma victim must be transported to a closer facility than a designated trauma center because of concerns for maternal survival, the emergency team at that facility must be prepared to make the acute management decisions, stabilize, and then transport to a higher level center.
Improved outcomes can be expected by following a coordinated approach among emergency medicine physicians, trauma surgeons, and obstetricians. Regardless of gestational age, all pregnant women who sustain or who are suspected to have sustained serious injuries should be first evaluated in the emergency department (ED) with the principle that maternal well-being is prioritized over fetal concerns. Maternal and fetal survival will depend on this coordinated team effort, which should begin as soon as the ED is notified that a pregnant trauma victim is being transported. Stabilization of the mother with identification of the maternal injury is the initial priority. Fetal evaluation and interventions can be conducted in the ED as needed. Pregnancy should not delay the decision to intubate, especially with the likelihood that surgical intervention will become necessary. The fetus is vulnerable to hypoxia, neurologic injury, or death; therefore all pregnant trauma victims should be provided with supplemental oxygen and avoidance of hypotension even if intubation is not required.
A suggested algorithm for care of the pregnant trauma patient is presented in Figure 26-2 .
Evaluation on Labor and Delivery
After clearance for severe maternal injury has been completed in the ED, the obstetrics team should provide a more thorough physical and obstetric assessment. A thorough physical examination should look for old and new ecchymosis and bruises over the entire body in the event the injuries might suggest violence as an origin. The vaginal examination can detect bleeding, rupture of membranes, and vaginal lacerations that can occur if there has been a pelvic fracture. An ultrasonographic examination should be performed early in the assessment to document fetal heart activity, viability, and gestational age. Depending on the labor and delivery gestational age criteria for assumption of care at the facility, the stable patient with trauma at or beyond 23 weeks’ gestation (the threshold of fetal viability) should be admitted to labor and delivery for further observation and monitoring for signs and symptoms of placental abruption and preterm labor. Women at fewer than 20 weeks’ gestation or prior to fetal viability can be evaluated for fetal life in the ED but do not necessarily require admission to labor and delivery. Based on the patient’s clinical presentation and uterine contraction frequency, the patient is observed for 4 to up to 24 hours prior to hospital discharge.
Fetal Monitoring
Fetal and uterine contraction monitoring is the most sensitive method for detecting abruptio placentae following trauma. In pregnant women who are beyond 23 to 24 weeks’ gestation, frequent uterine contractions are nearly always present in women who develop placental abruption following trauma. Moreover, a nonreassuring fetal heart rate (FHR) pattern may reflect maternal hemorrhagic shock or hypotension. Uterine contraction monitoring is unquestionably more sensitive than ultrasound in detecting placental abruption, and ultrasound detects only about 40% of abruptio placentae in the setting of trauma. Although several authors have recommended incorporating assessment of fetal status into the standard focused abdominal sonography for trauma (FAST) exam, it should not replace fetal monitoring. The standard FAST exam is performed to evaluate for intraperitoneal hemorrhage and has replaced diagnostic peritoneal lavage in many centers because of its excellent sensitivity (80% to 83%) for detection of intraperitoneal fluid. A fetal biophysical profile test and middle cerebral artery Doppler studies may be performed at the time of the FAST exam for further information regarding fetal well-being, although its ability to predict fetal outcome in the setting of trauma has not been thoroughly assessed. The FHR tracing has been called the “fifth vital sign” because it may provide the earliest evidence of maternal hypovolemia or hypotension ( Fig. 26-3 ). Likewise, frequent uterine contractions provide the most reliable warning sign of placental abruption or preterm labor.
