Learning Objectives:After participating in this continuing professional development activity, the provider should be better able to:
1. Describe the prevalence of trauma in pregnancy and the most common causes of trauma experienced by pregnant women.
2. Identify the physiologic and anatomic changes that occur during pregnancy to improve clinical management.
3. Outline the evaluation and management of pregnant women after trauma.
Trauma affects 6% to 8% of pregnancies and is the leading nonobstetric cause of maternal death.1,2 Pregnant trauma victims have been shown to have mortality rates nearly twice that of their nonpregnant counterparts.3 In addition to direct maternal effects, trauma is associated with adverse perinatal outcomes including spontaneous abortion, preterm birth, preterm, prelabor rupture of membranes (PPROM), uterine rupture, and placental abruption. Appropriate care of the pregnant trauma patient requires careful consideration of the anatomic and physiologic changes during pregnancy and how these changes can both mask and mimic injury.
Types of Trauma
Trauma in pregnancy is most commonly unintentional, with motor vehicle collisions (MVCs) and falls accounting for the majority of cases.4,5 However, intentional trauma, including domestic violence (DV) or intimate partner violence (IPV), homicide, and self-harm or suicide is important considerations.
DV/IPV are the most prevalent forms of intentional trauma during pregnancy.4,6 IPV is associated with an increased risk of adverse obstetric outcomes and is also a leading cause of maternal death.4 Accordingly, the American College of Obstetricians and Gynecologists (ACOG) recommends universal screening for IPV as part of routine obstetric care.7
Trauma can be further defined by mechanism, with blunt abdominal trauma being the leading type of traumatic injury during pregnancy. MVC is the most frequent cause of blunt trauma, with a reported incidence of 207 per 100,000 pregnancies.8 The degree of injury sustained in MVC varies widely and depends on the mechanism of the collision, vehicular velocities, and maternal seatbelt use. Pelvic fractures, along with placental abruption, are the most common causes of fetal death after MVCs.9
Slips and falls are frequently encountered by pregnant patients, particularly in the third trimester.5 Although significant injury after a fall is uncommon, increased joint laxity during pregnancy predisposes patients to musculoskeletal injury, including pelvic fracture. Pelvic fractures can result in direct fetal injury including skull fracture and penetrating brain injury with advancing gestation, and are also linked to significant maternal morbidity and mortality due to associated complications such as retroperitoneal hemorrhage and injury to adjacent organs.10 Notably, a stable pelvic fracture is not an absolute contraindication to vaginal delivery, but care should be taken to avoid any further damage to the pelvis from positioning during childbirth.
Penetrating trauma primarily includes injuries sustained through gunshot and stab wounds. Management of these patients depends largely on the site of injury. Penetrating insults to the abdomen become increasingly likely to cause uterine and fetal injury as gestational age increases, with reported fetal death rates as high as 73%.11 With cephalad displacement of the visceral organs, maternal bowel becomes less prone to injury with increasing gestational age.
Burns and electrocution-related injuries are not frequently reported in pregnancy. The morbidity of burns is largely dependent on depth and percentage of body surface area involved. Maternal and fetal mortality approaches 100% with burns involving more than 40% of total body surface area.12 Smoke inhalation is another important consideration in pregnant patients who have experienced burns, with a recommended low threshold to suspect carbon monoxide poisoning and provision of liberal oxygen supplementation.
Although the literature surrounding acute poisoning during pregnancy is limited, most cases result from intentional exposure.13 In fact, toxic ingestion is the most common method of self-harm and suicide attempts during pregnancy.14 Agents most frequently implicated in the case of acute poisoning include nonopioid analgesics and sedative-hypnotic medications.13,14
Categories of Trauma
During pregnancy, minor trauma, limited to minor bruising, lacerations, and contusions, requires only limited, targeted maternal evaluation and fetal assessment.4,15,16 However, major trauma leading to vital sign instability, loss of airway, or even cardiac arrest should alert the care team-ideally involving obstetricians and trauma physicians-of likely catastrophic trauma requiring initiation of advanced cardiac and trauma life support measures. The National Partnership for Maternal Safety has proposed the following vital sign parameters as "early warning criteria," intended to trigger a bedside evaluation by a physician with care escalation as appropriate: systolic blood pressure (BP) less than 90 or more than 160 mm Hg, diastolic BP more than 100 mm Hg, heart rate less than 50 or more than 120 beats per minute, respiratory rate less than 10 or more than 30 breaths per minute, or oxygen saturation less than 95% on room air.17
Challenges in Caring for the Pregnant Trauma Patient
A unique consideration when providing care to the pregnant trauma patient is the challenge of having not 1, but 2 patients-mother and fetus-to manage during resuscitative efforts. Furthermore, one must be familiar with the various anatomic and physiologic changes associated with pregnancy, as these may impact the patterns of injury and maternal response to trauma.
The uterus remains in the pelvis until approximately 12 weeks' gestation and, with increasing size, displaces neighboring pelvic and abdominal structures. At 20 weeks' gestation, the uterine fundus is expected to be at the level of the umbilicus, and at 34 weeks, the level of the costal margin. In the third trimester, blood flow to the uterus is as high as 600 mL/min, and pelvic vasculature is markedly dilated, increasing the likelihood for catastrophic hemorrhage after trauma.
The cardiovascular system undergoes multiple adaptations, all of which contribute to an increased cardiac output (CO) throughout pregnancy. Due to increased preload from increased blood volume, decreased afterload from declining peripheral vascular resistance, and the physiologic tachycardia of pregnancy-on average 15 to 20 beats per minute faster than outside of pregnancy-CO is typically 20% above baseline by approximately 8 weeks' gestation, and nearly 50% at term. Importantly, after 20 weeks' gestation, the gravid uterus has the potential to cause compression of the inferior vena cava in the maternal supine position, effectively decreasing preload and CO by as much as 10% to 30%.18 Therefore, when attempting to identify hemorrhagic shock, it is important to note that up to 30% to 35% of circulating blood volume may be lost before notable vital sign changes.19
The effects of progesterone on the pulmonary system manifest as early as the first trimester, with increased tidal volume and respiratory drive causing physiologic hyperventilation. As a result, pregnancy is a state of mild respiratory alkalosis, associated with a compensatory decrease in plasma bicarbonate. As such, a normal bicarbonate level in a pregnant patient is concerning for impending respiratory collapse. Oxygen consumption also increases by close to 20% during pregnancy. The gravid uterus causes elevation of the diaphragm by as much as 4 cm at term. Similarly, the upward displacement of the diaphragm decreases functional residual capacity, but also distorts typical anatomic points of reference, such that trauma to the chest may actually be intraabdominal in location. Furthermore, patients presenting with pneumothorax requiring thoracotomy tube placement may need the tube placed 1 to 2 interspaces higher than the usual fifth intercostal space.
Elevated progesterone in pregnancy also contributes to delayed gastrointestinal motility and decreased lower esophageal sphincter tone. These factors, in conjunction with increased intraabdominal pressure, contribute to an increased risk of aspiration, particularly in individuals undergoing endotracheal intubation. Thus, cricoid pressure and gastric decompression are important considerations to reduce this risk, especially in patients greater than 16 weeks' gestation with altered mental status.19
With respect to the renal system, both glomerular filtration rate and renal blood flow are markedly increased during pregnancy, resulting in a decreased serum creatinine level. Notable genitourinary changes include displacement of the bladder in both an anterior and superior direction, increasing susceptibility to traumatic injury. Additionally, hydronephrosis and hydroureter, typically more prominent on the patient's right side, are expected.
Pregnancy-related hematologic changes include an increase in plasma volume by approximately 50%, with an increase in red blood cell mass by only 20% to 30%. Together, these changes contribute to a dilutional anemia during pregnancy, with the lower limit of normal hemoglobin ranging from 11.0 g/dL in the first and third trimesters, to 10.5 g/dL in the second trimester. Other hematopoietic changes include a physiologic leukocytosis and slight decrease in the number of circulating platelets. Pregnancy is also a well-recognized procoagulant state, characterized by elevated fibrinogen to above levels of 400 mg/dL.
Clinical Management
Ultimately, care of the pregnant trauma patient should involve a multidisciplinary team with the primary goal of management being maternal stabilization, as fetal outcomes are known to directly correlate with early, aggressive maternal resuscitation.6 As a general principle, any diagnostic test or treatment required to save the mother's life or to address her critical status should be undertaken, even if the intervention under consideration is potentially disadvantageous to the fetus.
Primary Survey
The goals of the primary survey are to assess the ABCs-airway, breathing, and circulation-and to establish maternal cardiopulmonary stability. The cervical spine should be immobilized for patients who may have sustained a spinal cord injury. Patency of the airway should be confirmed immediately, and if not secured, early intubation is recommended. Intubation may be more challenging in the pregnant patient, given increased airway edema and inherent risk of aspiration. Oxygen supplementation should be provided, with a goal of maternal oxygen saturation (Sao2) at or above 95%.20 If Sao2 is below 95%, an arterial blood gas can be obtained, with a goal of maternal Pao2 more than 70% to maintain a favorable oxygen gradient across the placenta.
To ensure adequate circulation, displacement of the uterus toward the maternal left may be needed if the uterine fundus is at or above the umbilicus. This is best achieved by positioning the patient in left-lateral decubitus position, but tilting 30 degrees to the left or manual displacement may also be effective. Vascular access should be promptly established with 2 large-bore IVs and crystalloid infusion initiated, as vital sign abnormalities may not manifest until 15% to 20% of total maternal blood volume is lost. When significant blood loss is suspected or hemodynamic improvement is insufficient after 2 to 3 liters of crystalloid infusion, transfusion should be initiated per protocols similar to those used in nonpregnant trauma victims. The target fibrinogen level in a pregnant patient is more than 200 to 300 mg/dL.
Vasopressors should be an absolute last resort for management of maternal hypotension, given the profound impact these agents have at the level of the uteroplacental vasculature. Once the ABCs have been completed, the provider can proceed to assess "D" or "disability" 'referring to the patient's neurologic status. A focused neurologic examination should be performed, assessing level of consciousness, pupillary size and reactivity, gross motor function, and sensation. The Glasgow Coma Scale is a commonly used tool in this setting. The primary survey concludes with "E," representing "exposure." This refers to ensuring full exposure of the skin to allow for a comprehensive examination and identification of all potential signs of injury.
Secondary Survey
After completion of the primary survey and stabilization of the patient, the secondary survey is performed. This should include a head-to-toe physical examination and focused clinical history. Of note, classic peritoneal signs such as rebound tenderness and guarding may be blunted by the rectus diastasis and the gravid uterus' displacement of neighboring anatomic structures. The uterus should be palpated both for size and for areas of tenderness. Hypertonic, frequent contractions may signal placental abruption. Palpable fetal parts and uterine tenderness should trigger concern for a large uterine rupture.
In addition to relevant medical and surgical history, information about the mechanism and severity of the trauma is important. An obstetric history, including mode of delivery and any complications associated with prior pregnancies, should be ascertained. Additionally, complications in the current pregnancy including any known fetal anomalies or abnormalities related to placentation should be determined. One should also inquire specifically about abdominal trauma and obstetric symptoms, including loss of fluid, bleeding, contractions, and fetal movement. A pelvic examination is only necessary if clinically warranted. Lastly, time of last oral intake should be determined, particularly for patients who may undergo surgical intervention.
Fetal Assessment
Once catastrophic trauma has been excluded and maternal stability achieved, the obstetric provider can turn their attention to fetal assessment. Measurement of the fetal heart rate is the minimum initial fetal assessment to determine whether the fetus remains viable. It is critical to determine the fetal gestational age, as this is certain to impact management and subsequent plan of care. Whenever possible, prenatal records should be obtained and pregnancy dating criteria confirmed. If not feasible and gestational age remains unknown, a gross estimation can be made using fundal height or real-time fetal biometry. On bedside ultrasound, a summation of fetal measurements is most accurate, but a measurement of >=4-cm femur length has been demonstrated to be consistent with fetal viability.21
For gestations below the range of periviability (22-23 weeks), fetal heart rate is adequate for assessment. A normal fetal heart rate is 110 to 160 beats per minute. Care should be taken to measure fetal and maternal heart rates simultaneously to ensure that a fetal heart rate is truly being detected. For pregnant patients beyond the point of viability, electronic fetal monitoring with tocodynamometry should be initiated as soon as reasonably possible-ideally immediately after the abdomen and spine are examined and medically cleared. Although there is no established consensus regarding the duration of cardiotocography after trauma, multiple studies suggest a minimum of 4 hours' duration.22,23 Criteria for extending fetal monitoring to 24 hours include having 6 or more contractions in any single hour of monitoring, a nonreactive fetal heart rate tracing, vaginal bleeding and/or significant abdominal pain, or severe maternal injury. Importantly, even in the presence of a reassuring fetal heart tracing, a significant mechanism of injury (eg, car vs pedestrian) should factor into the need for prolonged monitoring.
Laboratory Tests
Depending on the degree of trauma, one should consider obtaining a complete blood count, type and screen, coagulation profile, and fibrinogen level. Toxicology screening may be appropriate. Expert consensus is that anti-D immune globulin should be routinely administered to Rh D-negative women who have experienced abdominal trauma.20,24,25 Per current ACOG guidelines, in addition to administering anti-D immune globulin to Rh D-negative women who have experienced abdominal trauma, quantification of fetal-maternal hemorrhage with a Kleihauer-Betke (KB) test should be obtained.24 If fetal-maternal hemorrhage has occurred, the KB test allows for calculation of the appropriate dose of anti-D immune globulin, with one standard 300-[mu]g vial protecting against 30 mL of fetal whole blood or 15 mL of fetal red blood cells in maternal circulation.26
Imaging Studies
Although clinically indicated imaging studies should not be delayed or withheld due to concerns for potential fetal effects, judicious use of diagnostic imaging should follow the "ALARA (as low as reasonably achievable) principle," so as to promote patient safety and avoid fetal harm.
Focused assessment with sonography for trauma (FAST) is a low-risk, efficient approach to evaluate for the presence of free fluid in the pericardium, the hepatorenal space, the perisplenic space, and the suprapubic area. A positive FAST in the context of a clinically unstable trauma patient is an indication to proceed with immediate exploratory laparotomy. Bedside ultrasound also has the capability of obtaining critical information about the patient's pregnancy, including confirmation of fetal cardiac activity, an estimate of gestational age, fetal number, fetal viability, and placental location. Fetal presentation and a gross assessment of amniotic fluid volume can also be rapidly determined. Although ultrasound can help determine placentation, its utility in evaluating for placental abruption is limited, with reported sensitivity for detecting abruption ranging from 24% to 57%.27-29 Ultimately, the diagnosis of a placental abruption is based on clinical or pathologic findings.
Imaging modalities involving ionizing radiation, including radiography and computed tomography, can provide information that often outweighs the radiation risk to the fetus. The vulnerability of a developing fetus is dependent on both gestational age at the time that the imaging study is performed and the dose of radiation. To date, there have been no reports of adverse pregnancy outcomes including teratogenicity, fetal growth restriction, and spontaneous abortion in patients exposed to radiation doses of less than 50 mGy.30
Oral contrast is not absorbed by the patient and has not been linked to any adverse fetal effects.31 Conversely, iodinated IV contrast crosses the placenta.31 Given the theoretical risk of iodinated contrast on the developing fetal thyroid gland, it is recommended that IV contrast be restricted to circumstances in which its use is absolutely required for diagnostic purposes and would influence the patient's management.30,31
Although MRI tends to be more sensitive than ultrasonography, and avoids the radiation exposure associated with CT, the time-intensive nature of the study limits its use in the acute trauma setting. MRI is however quite effective in visualizing soft-tissue structures and can be a useful ancillary study in the clinically stable patient suspected of having a non-life-threatening injury.
Obstetric Complications of Trauma
Placental Abruption
Classically, placental abruption is associated with vaginal bleeding, abdominal pain, and uterine tenderness, but it may also be more occult. Frequent uterine contractions or uterine hypertonicity may be the earliest findings suggestive of abruption. Although tocodynamometry showing uterine hypertonicity has the highest sensitivity for detecting placental abruption, there is no single diagnostic test that confirms the presence of an abruption. Rather, it is a clinical or pathologic diagnosis, and providers must have a high index of suspicion to detect it. Regardless of its presentation, abruption can lead to significant bleeding, hemodynamic instability, and development of a consumptive coagulopathy. Placental abruption increases the risk of fetal death, particularly with greater than 50% placental separation, but abruption more commonly leads to preterm labor.20,32 A trial of vaginal birth may be reasonable in patients who are hemodynamically stable and have a reassuring fetal heart rate tracing, but cesarean delivery is indicated if concerns regarding maternal or fetal status arise. Although placental abruption can lead to fetal demise, up to 60% of perinatal deaths are potentially preventable with early recognition of fetal distress and timely intervention with cesarean delivery.20
Uterine Rupture
Uterine rupture may occur in the context of both blunt and penetrating trauma but is a rare complication seen in less than 1% of trauma during pregnancy. The extent of injury sustained may range from serosal injury to complete, full-thickness rupture. The most significant risk factor for uterine rupture is a history of prior cesarean birth. Signs and symptoms indicative of significant uterine rupture include hemodynamic instability, abdominal pain and distension, irregular uterine contour with palpable fetal parts, and abnormalities on fetal cardiotocography. In the setting of uterine rupture, maternal mortality has been reported to be as high as 10%, whereas fetal mortality is nearly universal.19 Emergent surgical management is indicated if uterine rupture is suspected with the goal of controlling hemorrhage through repair of damaged structures, delivering the fetus if viable, and facilitating prompt resuscitation.
Preterm Labor
A host of factors may increase the risk of preterm labor in a patient who has experienced trauma. Trauma to the uterus may destabilize lysosomal enzymes and lead to increased prostaglandin production, subsequently leading to preterm labor.22 Prostaglandin release can also be triggered by the presence of bleeding in the context of placental abruption. In many cases, PPROM predisposes to preterm labor. The presence of regular contractions on cardiotocography in conjunction with cervical dilation suggests preterm labor.
Direct Fetal Injury
Direct fetal injury is relatively uncommon, as the uterus, maternal soft tissue, and amniotic fluid serve as protective factors. Blunt abdominal trauma in late gestation may involve the fetal skull and brain, particularly in the rare case of pelvic fracture. The pattern of fetal injury is less predictable in penetrating abdominal trauma. Fetal injuries, including fractures, may be seen on ultrasound or detected incidentally on other imaging modalities performed for maternal indications. If detected, fetal well-being should be assessed via cardiotocography and neonatology may be consulted, though-as in all cases-maternal stabilization should be prioritized.
Maternal Cardiopulmonary Arrest and Resuscitative Hysterotomy
Cardiac arrest in pregnant patients should follow the same Advanced Cardiac Life Support (ACLS) guidelines for nonpregnant patients in terms of chest compressions, rescue breaths, respiratory support, pharmacotherapy, and defibrillation. Given the effect of the gravid uterus on the large vessels, it is important to maintain left lateral uterine displacement when the uterine size exceeds 20 weeks' gestation. The American Heart Association recommends manual displacement of the uterus, as it allows for more effective compressions and enhanced ability to access the patient's airway.33
Historically, guidelines for management of maternal cardiopulmonary arrest for viable pregnancies followed a "4-minute rule" for initiating a perimortem cesarean delivery in the setting of unsuccessful maternal resuscitative efforts.34 A more modern approach is that of the "resuscitative hysterotomy," which optimizes both maternal and fetal health in parallel.35 Specifically, a resuscitative hysterotomy challenges the 4-minute rule and effectively replaces the term perimortem cesarean delivery, underscoring the notion that, if the uterus is palpable at or above the umbilicus, preparation for delivery should occur in conjunction with initiation of maternal resuscitative efforts. This approach emphasizes the mutual benefit to resuscitative efforts and optimization of both maternal and fetal outcomes. Notably, an important distinction between perimortem cesarean delivery, which typically is performed for fetal benefit, and resuscitative hysterotomy is that, even in the presence of confirmed intrauterine fetal demise, resuscitative hysterotomy facilitates aortocaval decompression and improved maternal hemodynamics.
This resuscitative hysterotomy approach recommends that, after immediate initiation of ACLS, a rapid estimate of gestational age is made. For pregnancies of at least 20 to 24 weeks' gestation, members of the care team should immediately be mobilized in preparation for potential delivery in conjunction with ongoing resuscitative efforts. In the case of nonshockable rhythms (eg, pulseless electrical activity and asystole), or if the return of spontaneous circulation does not occur within the first few minutes of resuscitation, the provider should proceed with immediate resuscitative hysterotomy regardless of fetal viability or time since the onset of cardiac arrest.35,36 Notably, if resuscitative hysterotomy has not occurred within 4 to 5 minutes and resuscitation is ongoing, there is still evidence to support its potential benefit; therefore, it should be considered.36 Once the decision has been made to proceed with resuscitative hysterotomy, there is no indication to transfer the patient to the operating room (OR). A scalpel is the only essential instrument in this setting, and if readily available, Betadine or an alternative antiseptic can be splashed across the operative area before incision.
Conclusion
The obstetrician-gynecologist is uniquely positioned to contribute to primary prevention of trauma in pregnancy by screening for IPV and providing education related to seatbelt use. Additionally, obstetrician-gynecologists play a key role in the acute trauma evaluation, given their specialized training, clinical skills, and unique knowledge of pregnancy-related changes. Ideally, all hospitals that provide care to pregnant patients should have established prehospital and inhospital protocols for caring for trauma victims and regular training for providers to maintain the highest quality care and optimization of maternal and fetal outcomes.
Practice Pearls
* Trauma in pregnancy is the leading nonobstetric cause of maternal death.
* Blunt abdominal trauma from MVCs, mechanical falls, and assaults account for the vast majority of trauma cases in pregnancy.
* Vital sign abnormalities may not manifest until 30% to 35% of maternal blood volume has been lost.
* All Rh D-negative patients should receive Rhogam after trauma at any gestational age.
* Use of diagnostic imaging should be determined based on maternal indication rather than concerns for fetal effects.
* The diagnosis of a placental abruption is a clinical one.
* A resuscitative hysterotomy should be undertaken in women at 20 weeks' gestation or more, if cardiopulmonary resuscitation has been unsuccessful after the first few minutes.
REFERENCES