Trauma in Pregnancy

Victor J. Hassid and Miren A. Schinco

Trauma is the primary cause of death in women of reproductive age and is the leading nonobstetric cause of both fetal and maternal death during pregnancy (1-4).

The majority of blunt trauma during pregnancy results from motor vehicle crashes, with the remainder being relatively evenly distributed between falls and assaults (3,4,9-13). Some authors report that up to 11% of women are vic­tims of physical abuse during pregnancy (14-17) and up to 31.5% of pregnant women admitted following trauma are victims of intentional injury (11). Dur­ing the third trimester, an altered center of gravity (caused by the enlarged uterus) combined with pelvic ligamentous laxity produces a degree of gait instability that makes the pregnant woman particularly susceptible to injury by falls (1,9). This represents the second most common mechanism of injury during pregnancy (13).

In a recent review of over 77,000 women of childbearing age in the American College of Surgeon’s National Trauma Data Bank, pregnant patients were signifi­cantly younger, more likely to be underinsured, and of African American or His­panic descent than their nonpregnant counterparts. While they were less likely to have used alcohol or illicit drugs, still 13% had been drinking and 20% had used drugs prior to their trauma. Although pregnant trauma patients were more likely to use seat belts, still only two thirds were restrained. After admission for a trauma, 5.1% of patients went on to delivery, three quarters within 24 hours and by cesarean section.

The foundation of trauma management in pregnancy is that “the best chance for fetal survival is to assure maternal survival” (5). The physician caring for a pregnant trauma patient should always remember that there are two patients. Initial treatment priorities for an injured pregnant patient remain the same as for the nonpregnant patient. The use of imaging studies should not be withheld because of pregnancy. Because the anatomic and physiologic alterations of preg­nancy can alter the gravid woman’s response to injury, an understanding of these changes is critical when approaching trauma management. Early communication between the trauma surgeon and the obstetrician is very important in order to optimize the management of the pregnant trauma patient.

OUTCOMES

Regardless of severity, trauma during pregnancy has been associated with spontaneous abortion, premature labor, uterine injury, placental abruption, maternal death, and low birth weight fetal loss. When comparing traumatized gravid women with nontrauma controls, for any injury, both maternal and fetal outcomes are worse, with progressively worse outcomes with higher injury severity score (ISS). Injuries associated with the highest maternal mortality are thoracoabdominal and pelvic followed by brain injuries. Women who sustain trauma, but do not deliver at that time, continue with significant risk of increased morbidity and mortality throughout their pregnancy and therefore require close monitoring (13).

Maternal predictors of fetal death consist of maternal factors (ISS >15, severe head injury, pelvic fractures, shock, hypoxemia, and absent fetal heart tones) and mechanisms of injury (auto-pedestrian collisions, maternal ejection, motorcycle collision, and lack of restraints) (18-21). Infants under 28 weeks’ ges­tational age appear to have the highest potential for complications, possibly due to their intolerance of maternal stress (13).

ANATOMIC AND PHYSIOLOGIC ALTERATIONS OF PREGNANCY

Anatomic Changes

Until approximately the 12th gestational week, the uterus remains in the pelvis, and by 20 weeks and 34 to 36 weeks, it reaches the umbilicus and the costal mar­gin, respectively.

During the second trimester, the uterus enlarges beyond its protected intrapelvic location, but the fetus remains mobile and protected by a generous amount of amniotic fluid; the amniotic fluid can be a source of embolism and disseminated intravascular coagulation following trauma if it gains access to the intravascular space.

By the third trimester, secondary to the location of the fetal head within the pelvis, pelvic fractures may result in fetal skull fracture or significant intracra­nial injury. Unlike the elastic myometrium, the placenta has little elasticity, which predisposes it to shear forces at the uteroplacental interface and placental abruption.

While interpreting pelvic x-rays, it is important to remember that the pubic symphysis widens to 4 to 8 mm and the sacroiliac joint spaces increase by the 7th month of gestation.

Cardiovascular System

Maternal cardiac output begins to increase during the first 10 weeks of preg­nancy, reaching a peak of 30% to 50% above nonpregnant levels by the latter part of the second trimester (22). After the 10th week of pregnancy, the car­diac output can be increased by 1.0 to 1.5 L per minute, due to the increase in plasma volume and decrease in vascular resistance of the uterus and pla­centa, which during the third trimester of pregnancy receive 20% of the patient’s cardiac output. During the same period, the cardiac output may be transiently lowered by aortocaval compression by the gravid uterus, resulting in decreased placental perfusion. This phenomenon, known as the supine hypotension syndrome, may be observed clinically in otherwise normal preg­nant patients (22,23). It is very important to remember while managing a pregnant trauma patient that changing the maternal position from the supine to the left lateral decubitus position may increase cardiac output by as much as 25% at term (23).

The average maternal heart rate increases 20% to 30% during pregnancy such that by term, the normal maternal pulse rate is 80 to 95 beats per min­ute, making borderline tachycardia difficult to evaluate (2,9,14,23). Mean arterial blood pressure gradually declines during the first two trimesters of pregnancy, reaching its nadir by approximately 28 weeks’ gestation (22).

FIGURE 4.1 Compartmentalization of intestines during pregnancy and sites of gunshot wounds above and below the umbilicus.

Systolic arterial pressure decreases by 0 to 15 mm Hg, whereas diastolic pres­sure declines by 10 to 20 mm Hg, creating a widened pulse pressure. These changes are the result of diminishing peripheral vascular resistance and should not be mistaken as evidence of hypovolemia during the first two tri­mesters of pregnancy. During the third trimester, blood pressure gradually increases, returning to pre-pregnancy levels near term (2,7,9,22,23). Hyper­tension, systolic or diastolic, is never expected during pregnancy and, if present, may either be a response to pain, anxiety, or injury or be the result of a direct complication of pregnancy such as pregnancy-induced hypertension (9).

Associated with the underlying decreased peripheral vascular resistance of the first two trimesters of pregnancy is a paradoxical response to stimuli that would normally cause vasoconstriction. This altered response causes the skin to be warm and dry, instead of cool and clammy which would be expected during hypovolemic shock (9). In addition, central venous pressure, normally approximately 9cm ^O in the nonpregnant patient, gradually decreases throughout pregnancy until it reaches 4 to 6 cm ^O during the third trimester (4,7,14,24). Venous hypertension in the lower extremities is present during the third trimester.

Total maternal blood volume increases by as much as 50% at 34 weeks’ ges­tation, improving maternal response to hemorrhage.

Electrocardiographic (ECG) changes in late pregnancy are not specific and reflect the leftward shift of the cardiac axis, by approximately 15 degrees, due to diaphragm elevation. The T waves may be flattened and inverted in lead III, and the Q waves may appear in leads III and aVF. Supraventricular ectopic beats may also be seen (9,14).

Respiratory System

Minute ventilation increases by 40% to 50% over control values at term due to increases in tidal volume and respiratory rate (9,14,22,25). The metabolic effect of this change is a partially compensated respiratory alkalosis, with arterial blood gases showing a decrease in PCO2 to approximately 30 to 34 mm Hg and a decrease in serum bicarbonate to 18 to 22 mEq∕L. The net effect is to leave the pregnant woman with a decreased buffering capacity after trauma (1,9,22).

Gastrointestinal System

The major physiologic alterations of the gastrointestinal system are those of increasing compartmentalization of the small intestine into the upper abdomen and a progesterone-induced decrease in gastrointestinal motility. The gravid uterus may protect the abdominal viscera from injury to the lower abdomen, but penetrating wounds to the upper abdomen may injure many loops of tightly crowded small intestine (Fig. 4.1). In addition, stretching of the abdominal wall alters the normal response to peritoneal irritation, at times masking significant intra-abdominal organ injury. Decreased gastric emptying increases the possi­bility of aspiration during trauma and intubation, therefore early gastric tube decompression is important in order to prevent aspiration of gastric contents (1,7,9,22,24,25). Position of the patient’s spleen and liver is essentially unchanged by pregnancy.

Urinary System

Progesterone-induced smooth muscle relaxation of the ureters and mechanical compression by the gravid uterus cause dilatation of the ureters and renal pel- vises, which may appear as hydronephrosis on radiographic studies (14,22). In addition, ureteropelvic dilatation predisposes the urinary collecting system to stasis and subsequent infection, particularly after catheterization (14,22). Ana­tomically, the urinary bladder is displaced anteriorly and superiorly by the enlarg­ing uterus, making it increasingly vulnerable to injury after the first trimester (1,2,8,22). Furthermore, the glomerular filtration rate and the renal plasma blood flow increase during pregnancy and the levels of creatinine and serum urea nitro­gen drop to approximately one half of normal pre-pregnancy levels.

Endocrine System

The pituitary gland increases in size and weight by 30% to 50% during pregnancy, and any significant drop in blood pressure can result in necrosis of the anterior pituitary gland and subsequent pituitary insufficiency.

Neurologic System

One of the complications of late pregnancy is eclampsia, which can present with the same signs and symptoms as a head injury. It should always be considered in case of seizures associated with hypertension, hyperreflexia, proteinuria, and peripheral edema. It may be necessary to obtain expert neurologic consultation in these cases in order to differentiate between eclampsia and other causes of seizures.

Table 4.1 outlines the physiologic, anatomic, and laboratory changes asso­ciated with pregnancy.

Patterns of maternal and fetal injury

Blunt Abdominal Trauma

Following blunt abdominal trauma during the latter part of pregnancy, the gravid uterus is subject to direct injury, as well as to the shearing forces resulting from sudden deceleration. Most fetal morbidity is a result of cata­strophic maternal trauma; however, some serious complications, including preterm delivery, abruptio placentae, fetal injury, fetal death, and massive fetomaternal hemorrhage (FMH), have occurred after seemingly minor injuries (5,11,26,27).

The abdominal wall, uterine myometrium, and amniotic fluid act as buffers to direct fetal injury from blunt trauma. Still, fetal injuries can occur when the abdominal wall strikes the dashboard or steering wheel, or in case, the pregnant patient is struck by a blunt instrument. Indirect fetal injury may take place secondary to rapid deceleration, contrecoup effect, or a shearing force leading to placental abruption.

TABLE

4.1

Physiologic and Anatomic Changes in Pregnancy

Note: ↑ Increased; T decreased. WBC, white blood cell.

Abruptio placentae is a significant cause of fetal loss in both catastrophic and noncatastrophic trauma. While the exact mechanism of traumatic abruption is not known, the suggested mechanism is based on the funda­mental differences in tissue characteristics between the relatively elastic myometrium of the uterus and the relatively inelastic tissue of the placenta. When an external deforming force is applied to the abdomen, shearing of the uteroplacental interface occurs. Shearing is further aggravated by the increased intrauterine pressure that results from impact (10,15). Signs and symptoms suggesting abruption include vaginal bleeding, uterine tender­ness or contractions, fetal heart rate abnormalities, and fetal death. Although the presence of these symptoms is significant, the absence of symptoms fol­lowing trauma does not exclude the possibility of placental abruption (3,27-29). Most cases of significant abruption can be identified by clinical signs or electronic fetal monitoring within 4 to 6 hours of the traumatic event (15,23,30), however, even in minor abdominal trauma, significant placen­tal abruption can occur without significant symptoms. This supports the i mportance of fetal monitoring after abdominal trauma (20). Cases of abruptio placentae have been reported to occur up to 5 days following severe trauma (29,31).

Uterine rupture may also result from blunt trauma. Uterine rupture com­plicates approximately 0.6% of traumatic events during pregnancy and tends to occur only with major blunt abdominal trauma (15,23). The presentation of uter­ine rupture ranges from subtle findings such as uterine tenderness and worri­some fetal heart rate patterns, without changes in maternal vital signs, to rapid onset of maternal hypovolemic shock associated with fetal and maternal death (15). Fetal mortality rate approaches 100%; maternal mortality is usually due to concurrent injury (23).

Amniotic fluid embolism is a rare complication of pregnancy characterized by poor response to treatment and high mortality. The incidence is between 1 in 8,000 and 1 in 80,000 live births with mortality ranging from 61% to 86%. While it most frequently occurs in the peripartum period, it has also been described after blunt abdominal trauma. It typically presents with sudden onset of hypoxia, altered mental status, hemody namic compromise, and disseminated intravas­cular coagulation. The diagnosis remains largely a clinical one. Management is mainly nonspecific supportive therapy aimed at cardiopulmonary resuscitation, correction of coagulopathy, and treatment of hemorrhage. If delivery has not occurred, emergent cesarean section prevents further hypoxic insult to the fetus and facilitates treatment of the mother (32).

Premature uterine contractions are another common sequela of maternal trauma (1,3,30-31,33-36). Studies have shown that up to two thirds of trauma­tized gravidas experience frequent contractions during the initial 4 hours of monitoring (3,30,34). Postulated etiologies include placental abruption, uterine contusion, membrane ischemia, and membrane rupture (1). The use of tocolytics to halt premature contractions associated with trauma is controversial. Although some authors report successful cessation of preterm contractions with these agents (36,37), others discourage their use, believing that regular uterine activity after trauma will spontaneously subside during observation. In those cases in which contractions persist, placental abruption must be considered until proven otherwise (14,34). Although the mean abdominal abbreviated injury score (aAIS), a direct indicator of injury severity of intra-abdominal structures, is usually higher among patients who sustained acute termination of pregnancy and/or fetal loss, in some studies, a high aAIS (≥3) did not independently predict these complications (38).

Direct fetal injury complicates the effectiveness of seat belts during pregnancy (50).

Penetrating Abdominal Trauma

Gunshot and stab wounds are the most frequently encountered penetrating inju­ries (14,22). As with blunt trauma, pregnancy often changes the usual manifesta­tions of penetrating abdominal trauma because the gravid uterus displaces other abdominal organs cephalad. When the route of entry is below the fundus, the gravid uterus will often protect maternal viscera by absorbing the force of the shell or instrument. In contrast, upper abdominal injuries may result in increased injury to bowel compressed into the upper abdomen (14,22).

Gunshot wounds to the abdomen are associated with a high rate of internal organ injury. When a bullet, particularly one of low velocity such as that com­monly found in civilian injuries, strikes the pregnant uterus, much of its energy is dissipated in the dense uterine musculature, diminishing its velocity and abil­ity to penetrate other maternal abdominal organs. Gunshot wounds to the preg­nant abdomen therefore are associated with low maternal rates of morbidity and mortality (4,24,53). Fetal outcome, however, is generally poor, with reported rates of fetal injury varying from 59% to 78% and perinatal mortality ranging from 41% to 71% (1,22,24,39,53). Fetal mortality is caused by both prematurity and direct fetal injury (24). Although direct fetal injury portends a poor progno­sis, cases have been reported in which a fetus having sustained a nonfatal injury later was successfully delivered alive (7,24,54). Because gunshot wounds to the abdomen have a high frequency of internal organ injury, surgical exploration remains the standard approach to this type of injuries (4,15,16,22).

Stab wounds to the abdomen are associated with a lower mortality rate than are gunshot wounds. As with gunshot wounds, the gravid uterus may pro­tect the victim of a lower abdominal stab wound, whereas wounds to the upper abdomen carry a higher incidence of visceral injury (4,7,15,22). The trend toward conservative management of abdominal stab wounds extends to the pregnant patient. Clinical considerations influencing management include gestational age, condition of the mother and the fetus, and location of the wound in the abdo­men. Management options include immediate surgical exploration, in case of diffuse abdominal tenderness or presence of peritonitis, or close observation and use of adjunctive imaging studies, which may provide information regard­ing potentially injured viscera and penetration or not of the abdominal fascia.

EVALUATION AND MANAGEMENT

Initial evaluation and resuscitative efforts should be directed toward the mother, because the most common cause of traumatic fetal death is maternal death. Once maternal airway, respiratory, and hemodynamic stability are ensured, attention must be immediately directed to assessment and assurance of fetal health.

Prehospital Management

Injured pregnant women, particularly those in the latter half of pregnancy, should be transported to an appropriately designated trauma center with facili­ties for adequate maternal and specialized neonatal care when possible (4,9). During the second and third trimesters, transport should be performed with the patient in the left lateral decubitus position or the spine must be immobilized, with the backboard tilted 15 degrees to the left (1,7,9,14). Listening for fetal heart tones may be performed en route but should not delay transport (7,14). The pneu­matic antishock garment (PASG) may be used to control bleeding from pelvic or lower extremity fractures, but its use should not interfere with rapid reestablish­ment of intravascular volume by intravenous fluid infusion. If it is used during pregnancy, only the lower or leg compartments should be inflated. Inflation of the abdominal compartment is contraindicated in any patient with a potentially salvageable gestation because the PASG has a deleterious effect on uteroplacen­tal blood flow, compromises maternal venous return, and has the potential to cause direct fetal injury (1,4,7,9,22,23).

Both in the prehospital setting and in the emergency department, oxygen therapy provides special benefit for the fetus. Although the maternal arterial blood is normally well saturated with oxygen when the mother is breathing room air, the oxygen hemoglobin dissociation curve of fetal blood is shifted such that increasing alveolar oxygen tension continues to improve fetal saturation and thereby fetal outcome (7,14). Maternal hemorrhage can reduce uterine blood flow 10% to 20% before signs of maternal hypovolemia appear (1,4,5,9). Therefore, early intravenous access and volume resuscitation are important for both the mother and the fetus. Vasopressors should be avoided, because they can further decrease uterine blood flow (4,7,15). The presence of initial maternal hypotension (defined as systolic blood pressure ≤90 mm Hg) has been shown to be associated with a higher risk of pregnancy loss. Toward the third trimester, maternal intra­vascular volume increases up to 50%. This improves maternal tolerance of hem­orrhage and delays the appearance of signs and symptoms of shock, while the uterine circulation is reduced. Once obvious maternal hypotension ensues, the fetus has already been endangered by decreased uterine arterial blood flow (55).

Evaluation of the Mother and the Fetus

Prehospital information is critical in ascertaining the mechanism of injury, vital signs, and patient condition in the field. Prenatal history is of particular impor­tance, particularly in ascertaining the gestational age of the fetus and the pres­ence of complicating medical conditions. Maternal perception of fetal movement may provide a very cursory indication of fetal health. The time of the last meal is more significant than in the nonpregnant patient because of the prolonged gastric emptying time associated with pregnancy (7,9).

Initial physical assessment of the mother is focused on the stability of the airway, adequacy of ventilation, effectiveness of the circulatory volume, and evalu­ation for occult injuries; there exist conflicting data regarding the relationship between the mother’s Glascow Coma Scale (GCS) and the fetal outcome (56). Sup­plemental oxygen should be administered to the mother throughout the initial resuscitation and evaluation, because minimal changes in maternal oxygenation result in appreciable changes in fetal oxygen content and reserve (4,14,25). Because of the increased potential for aspiration and importance of fetal oxygenation, endotracheal intubation should be pursued more aggressively than in the nonpreg­nant patient (4,15,22,25). The expanded maternal intravascular volume associated with pregnancy may delay the onset of clinical signs of shock, so fluid resuscitation should be more aggressive than in nongravid patients. Crystalloid fluid resuscita­tion and early type-specific blood administration are indicated to support the physiologic hypervolemia of pregnancy. Non-cross-matched type 0, Rh D-negative blood can be used if type-specific blood is not immediately available (16,23). Con­tinuous uterine displacement, either manually or by placing the mother in the left lateral tilt position, is desirable after 20 weeks’ gestation, because of the uterine compression of the inferior vena cava. Vasopressors should be avoided until appro­priate volume replacement, including blood transfusion if indicated, has been administered (4,14,15,22).

Once maternal hemodynamic stability has been established and assessment of maternal injuries has begun, the condition of the fetus should be ascertained. Fetal evaluation includes determining fetal heart rate and fetal movement, evaluating uterine size and irritability, and examining the vagina for vaginal bleed­ing or leakage of amniotic fluid. Ideally, fetal heart rate and maternal contractions should be continuously monitored using external tococardiography. However, when this is not available, fetal heart tones should be auscultated at frequent inter­vals. Fetal heart rate abnormalities including tachycardia, late decelerations, and ultimately fetal bradycardia, even in the absence of vaginal bleeding and uterine tenderness or irritability, are highly suggestive of placental abruption (4,14).

Determination of fetal age and maturity may be critical in management decisions for the fetus. The quickest means of estimating gestational age is by palpation of the fundal height. At 12 weeks’ gestation, the uterine fundus rises just above the symphysis pubis; at 20 weeks’ gestation, it reaches the level of the umbilicus; and by 36 weeks of gestation, it lies just below the xiphoid process. The age of fetal viability is generally considered to be 24 to 26 weeks’ gestation, depending, in part, on the neonatal facilities available (1,2,7). Palpation of the uterine fundus two to three finger-breadths above the umbilicus is consistent with the presence of a potentially viable fetus. Ultrasound is a more accurate tool and should be used if circumstances permit (4,14).

Asymptomatic patients with minor or insignificant abdominal trauma may be discharged with reassurance after 4 to 6 hours of fetal and maternal monitor­ing. Discharge instructions should include the need to return upon the develop­ment of abdominal pain, decreased fetal movement, vaginal bleeding, or leakage of fluid. Timely obstetric follow-up is advised (15,16).

Routine Laboratory Studies

Urine β-human chorionic gonadotropin testing should be performed on all female trauma patients of childbearing age who are not obviously pregnant, as approxi­mately 3% of females admitted to a trauma center are pregnant, and 8% of these pregnancies are newly diagnosed (57,58). Routine laboratory studies in the preg­nant patient with significant trauma include type and cross-match; complete blood count with platelet count; electrolytes; and coagulation panel including prothrombin time, partial thromboplastin time, fibrinogen level, and fibrin degra­dation products (1,9,14,16,23). The finding of a normal nonpregnant value of fibrin­ogen (200 to 250 mg/dL) may be consistent with early disseminated intravascular coagulopathy (14), because normal fibrinogen levels during pregnancy may be twice that in nonpregnant women. Rh D-negative patients typically will undergo K-B testing to determine the volume of FMH that has occurred (14,15,22,36,43).

Radiographic Procedures

The first trimester of intrauterine development is the time of greatest sensitivity to radiation (59). During the first 2 weeks of conception, the embryo is particu­larly sensitive to the lethal effects of radiation but has a low probability of sus­taining teratogenic effects if implantation and continued development occur (60,61). During the period of embryonic development (2 to 8 weeks after conception), the embryo is particularly sensitive to the growth-retarding and teratogenic effects of radiation; from the 8th to the 15th week after conception, the fetal brain is undergoing rapid neuron development and is potentially vul­nerable to radiation-induced mental defects. Throughout gestation, there is an increased risk of childhood malignancies, especially leukemia, in children exposed to radiation in utero (60-62). Determining the exact incidence of adverse effects, however, is difficult because of the prevalence of congenital mal­formations occurring in the general population and because of the other fre­quent biomedical and social factors that may influence pregnancy outcome (59,60). In general, fetal risk is considered negligible when the total radiation exposure is ≤5 rad and the risk of malformations is significantly increased above the control levels only at doses >10 to 15 rad (14,15,48,63). An increased risk of childhood cancers has been found at somewhat lower radiation doses (22,60,62). The dose of radiation absorbed by the fetus depends on several factors including the (a) energy and intensity of the x-rays, (b) proximity of the uterus to the ana­tomic area exposed, (c) extent of the area exposed, (d) patient positioning, (e) depth of the fetus, and (f) number of films acquired (64). If the uterus is out­side the area radiographed, the dose of radiation to the conceptus is limited to that delivered by scatter and leakage radiation, declining rapidly farther the uterus is from the radiographed area. Pelvic shielding should be used whenever possible (9). Estimates of fetal radiation exposure from commonly used proce­dures are listed in Table 4.2. Routine diagnostic radiographs seldom result in significant radiation exposure to the fetus. Therefore, although unnecessary

Estimated Radiation Dose to the Uterus From Commonly Used Radiographic Examinations