Chapter 256: Trauma in Pregnancy

Trauma remains the leading cause of nonobstetric morbidity and mortality in pregnant women.¹ The severity of maternal injuries may be a poor predictor of fetal distress and outcome after a traumatic event (even minor ones). Trauma during pregnancy is associated with an increased risk of preterm labor, placental abruption, fetomaternal hemorrhage, and pregnancy loss. Achieving successful outcomes for both mother and fetus requires a collaborative effort by the prehospital provider, emergency physician, trauma surgeon, obstetrician, and neonatologist.

Trauma during pregnancy is common. One study estimated that 32,810 pregnant women sustain injuries in motor vehicle crashes every year in the United States, a rate of 9 per 1000 live births.² Motor vehicle crashes are the most common cause of blunt abdominal trauma, accounting for up to 70% of acute injuries. This is followed by falls and direct assault in decreasing order of frequency.³ The incidence of falls appears to increase with the advancement of pregnancy, presumably due to alterations in maternal balance and coordination. Penetrating injuries are less common than blunt trauma during pregnancy.

Physiologic changes in pregnancy are discussed in detail in chapter 25, "Resuscitation in Pregnancy." In addition to normal physiologic changes, conditions such as pregnancy-induced hypertension, placenta previa, pre-eclampsia, and eclampsia may significantly alter the presentation and complicate evaluation and treatment in the setting of trauma (see chapter 100, "Maternal Emergencies after 20 Weeks of Pregnancy and in the Postpartum Period").

Table 25-1 summarizes important physiologic changes in pregnancy that affect resuscitation. Maternal blood volume expands at approximately week 10 of gestation and peaks at about a 45% increase from baseline at week 28. Because plasma volume increases more than red cell mass, mild physiologic anemia may be evident. Cardiac output increases by 1.0 to 1.5 L/min at week 10 of pregnancy and remains elevated until the end of pregnancy. Heart rate in the mother is generally increased by 10 to 20 beats/min in the second trimester, accompanied by decreases in systolic and diastolic blood pressures of 10 to 15 mm Hg.

The relative hypervolemic state can mislead the clinician during maternal resuscitation after trauma and make clinical findings difficult to interpret. A pregnant patient may lose 30% to 35% of circulating blood volume before manifesting hypotension or clinical signs of shock. Uterine blood flow is directly proportional to maternal mean arterial pressure, so maintain and replace maternal blood volume aggressively and adequately.

After week 12 of gestation, the uterus becomes an intra-abdominal organ, removing it from the relative protection of the maternal pelvis and making it susceptible to direct injury. The bladder moves anteriorly into the abdomen in the third trimester of pregnancy, increasing its vulnerability to injury. Uterine blood flow may increase to upward of 600 mL/min; severe maternal hemorrhage from uterine injury enters the equation at this point. The gravid uterus also causes passive stretching of the abdominal wall and peritoneum as it enlarges, and this may lead to diminished sensitivity to injury and irritation from intraperitoneal blood. At approximately weeks 18 to 20 of gestation, the expanding mass of the gravid uterus may put the mother at risk for the "supine hypotension syndrome," in which venous return and cardiac output are diminished by compression of the maternal inferior vena cava in the supine position. The enlarging uterus may also cause engorgement of lower extremity and lower abdominal vessels, which predisposes the patient to severe retroperitoneal injury. Avoid placing IV lines in the femoral region and lower extremity because of inferior vena cava compression by the uterus and the possibility of pooling in engorged or injured pelvic veins.

As pregnancy progresses, the diaphragm elevates by as much as 4 cm, and tidal volume increases by 40% as residual volume diminishes by 25%. These changes may significantly impair the ability of a pregnant trauma patient to compensate for respiratory compromise and can result in rapid development of hypoxia from pulmonary disorders or during intubation. Consider diaphragmatic elevation when thoracostomy tube placement is indicated during maternal resuscitation.

Gastric emptying is delayed, increasing the likelihood of gastroesophageal reflux and the potential for aspiration from acute injuries or endotracheal intubation. The small bowel is moved upward in the abdomen by the enlarging uterus, which increases the chance of complex bowel injuries in penetrating trauma of the upper abdomen.⁴ The liver is typically unaffected by pregnancy, and the most common cause of abdominal hemorrhage remains splenic injury, as in nonpregnant patients.

Rapidly assess gestational age by palpating uterine fundal height. At week 12 of gestation, the uterine fundus is at or about the level of the pubic symphysis, and at week 20, it is at the umbilicus. The uterus then expands approximately 1 cm beyond the umbilicus per additional week of gestation. Assessing fetal age helps determine fetal viability. Gestation ≥24 weeks is compatible with fetal viability. Examine the abdomen and uterus for evidence of injury as well as for uterine tenderness or contractions. Placental abruption may be suggested by a rigid, boardlike uterus, or no signs may be evident at all.

MATERNAL AND FETAL INJURIES

Direct fetal injury is relatively rare in blunt abdominal trauma during the first trimester. When fetal injuries do occur, they are typically seen later in gestation and tend to involve the fetal skull and brain. Such injuries can be sustained in association with fractures to the maternal pelvis when the fetal head is engaged. When the uterus is penetrated by a sharp object or projectile, the fetus can be injured.

Uterine rupture accounts for <1% of all injuries in pregnancy and is more likely to occur during the late second and third trimesters and when there is direct and forceful impact on the uterus.³ The fetal mortality rate is high. The clinical presentation of uterine rupture is quite nonspecific, but loss of the palpable uterine contour, ease of palpation of fetal parts, or radiologic evidence of abnormal fetal location suggests the diagnosis.

Uterine irritability and the onset of preterm labor may be precipitated by acute abdominal trauma during pregnancy. The use of tocolytic agents to manage premature labor in pregnant trauma patients is not generally recommended, so consult an obstetrician before considering tocolytics. Tocolytic agents have numerous adverse side effects, such as fetal and maternal tachycardia, that may complicate trauma evaluation.

Placental abruption is second only to maternal death as the most common cause of fetal death (Figure 256-1). Placental abruption complicates 1% to 5% of minor injuries during pregnancy and up to 40% to 50% of major traumatic injuries. During direct abdominal or deceleration injury, intrauterine pressures increase, the relatively elastic uterus deforms at the relatively inelastic placenta, and the placenta shears from the uterine wall. Even "minor" maternal injuries such as minor motor vehicle crashes, falls, and assaults can be associated with placental abruption and sudden fetal demise.⁵ The most sensitive clinical finding for placental abruption after trauma is uterine irritability (more than three contractions per hour), most evident immediately after trauma, on initial presentation to the ED.^5,6 Other clinical findings of placental abruption include abdominal pain, painful vaginal bleeding, and tetanic uterine contractions. Placental abruption may also lead to the introduction of placental products into the maternal circulation, stimulating disseminated intravascular coagulation or amniotic fluid embolism.

Fetomaternal hemorrhage is the entry of fetal red blood cells into the maternal blood stream and should be assumed in the setting of maternal trauma. If the mother is Rh negative and the fetus is Rh positive, if as little as 0.1 μL of fetal blood enters the maternal circulation, it can sensitize the mother⁷ and endanger the pregnancy and subsequent pregnancies. This is the basis for administering Rho(D) immunoglobulin to Rh-negative mothers after maternal trauma.

Prehospital care providers should ask about the possibility of pregnancy when evaluating injured women of childbearing age. Prioritize attention to the fundamentals of resuscitation (airway, breathing, circulation) in the mother. Administer supplemental oxygen because compensation for hypoxia is limited in pregnancy. Similarly, consider early endotracheal intubation when indicated by the nature or severity of injuries. Establish peripheral IV lines, and provide 50% more volume than would be given to the nonpregnant patient.

For patients at >20 weeks of gestation who must be transported in the supine position or in whom spinal immobilization is indicated, place a wedge under the right hip area, tilting the patient approximately 30 degrees to the left, to prevent hypotension from inferior vena cava compression by the gravid uterus. Triage to a hospital with trauma, obstetric, and neonatal services if at all possible.^4,8

Follow the traditional airway, breathing, circulation, disability, and exposure assessment for maternal injury, and simultaneously stabilize and resuscitate the mother. After completing the primary survey and performing resuscitative steps, proceed with secondary assessment.

ULTRASOUND

Begin with bedside expanded focused assessment with sonography for trauma to identify intra-abdominal or thoracic injury, and identify fetal activity and fetal heart rate. Transvaginal US can be performed once the mother is stabilized to complete the fetal survey and identify placental location. The sensitivity and specificity of abdominal US for the detection of intraperitoneal fluid are similar in pregnant and nonpregnant patients.⁹

RADIOGRAPHS

Carefully select imaging studies to minimize fetal exposure to the potential adverse effects of ionizing radiation. Do not withhold imaging needed for appropriate maternal trauma management. The greatest risk to fetal viability from ionizing radiation is within the first 2 weeks after conception, and the highest potential for malformation is during embryonic organogenesis from 2 to 8 weeks after conception. The risk of CNS teratogenesis is highest when exposure occurs between weeks 8 and 15 (see Table 99-9). A dose <5 rad is the threshold for human teratogenesis.⁹ Fetal exposure can be decreased by shielding the maternal abdomen and pelvis during many studies and by performing modified studies and using dose-reducing techniques, such as decreasing the number of imaging slices obtained.

Standard trauma plain radiographs, such as cervical spine, chest, and pelvis films, deliver <1 rad (10 mGy) each. Abdominopelvic CT and pelvic angiography result in the highest delivered doses of radiation. The amount is typically 2.5 to 3.5 rad (25 to 35 mGy), with some variation due to equipment quality, techniques used, and duration of study. If abdominal-pelvic CT scanning is necessary to evaluate maternal status, CT also detects placental abruption, with a reported sensitivity of 86% and specificity of 98% for abruption.¹⁰ Table 99-10 provides the estimated amounts of fetal radiation exposure for some common trauma imaging studies.¹¹

Potential effects of contrast agents employed in CT scanning are not well studied, and their use requires individualization, because iodinated agents can potentially cause neonatal hypothyroidism.

PELVIC EXAMINATION

Perform pelvic examination only after US to determine placental location and exclude placenta previa.⁶ Do not perform pelvic examination if placenta previa is identified. A sterile pelvic examination can identify injuries of the lower genital tract, vaginal bleeding, and rupture of amniotic membranes.

To assess for amniotic membrane rupture, test vaginal fluid with pH paper. Fluid in the vagina with a pH of 7 is suggestive of amniotic fluid, whereas fluid with a pH of 5 is consistent with vaginal secretions. A branchlike pattern, or "ferning," seen upon drying of vaginal fluid on a microscope slide, also suggests amniotic fluid.

LABORATORY TESTING

Obtain a CBC, serum chemistries, blood type and Rh status, coagulation profiles with fibrin degradation products and fibrinogen to assess for disseminated intravascular coagulation, and additional laboratory studies as clinically indicated. An Apt test or Kleihauer-Betke test can be performed by the laboratory. The Apt test is a qualitative determination of the presence of fetal hemoglobin in maternal blood. The Kleihauer-Betke test applies acid elution to an aliquot of maternal blood, and then maternal and fetal red blood cells are counted under the microscope. An extrapolation is then made regarding the volume of fetomaternal hemorrhage.

Serial Kleihauer-Betke testing can assess ongoing fetomaternal transfusion. If there is doubt whether the woman is pregnant or not, confirm pregnancy at the bedside with qualitative urine testing or with point-of-care US.

For pregnant trauma patients >20 weeks gestation (clinically identified by uterus at or above the umbilicus), obtain bedside US to assess fetal size, heart rate, gestational age, amniotic fluid volume, placental location, and fetal activity or demise. Fetal viability is ≥24 weeks' gestation. Normal fetal heart rate is 120 to 160 beats/min. US may not detect uterine rupture or fetal-placental injuries, does not monitor for fetal distress, and is not sensitive for placental abruption.^5,12 US sensitivity for placental abruption is about 25%, although specificity is >90%.¹²

Even for women ≥20 weeks, gestation with "minor" direct or indirect abdominal trauma, as soon as possible apply cardiotochodynamometry to monitor uterine contractions and fetal heart rate pattern. Decelerations, tachycardia, and bradycardia are signs of fetal distress. The most sensitive clinical finding for placental abruption after trauma is uterine irritability, which is frequent uterine contractions (more than three uterine contractions in an hour).^5,6 Fetal distress and demise can occur quickly and abruptly, so vigilant monitoring is necessary. If fetal heart tones are confirmed to be absent, then direct the remainder of treatment efforts solely at maternal resuscitation.¹¹

Develop a protocol involving the ED, trauma service, obstetrician, and obstetrics nurse for major trauma. For minor direct or indirect abdominal trauma (such as minor motor vehicle accident, simple fall, or assault), a simpler protocol involving ED and the obstetrics team is effective. Because most emergency physicians are unfamiliar with the patterns of early, late, and variable decelerations, the labor and delivery nurse is an essential part of the ED monitoring team. In case of fetal deterioration, the labor and delivery nurse can identify the need for emergency cesarean section.

Follow the standard steps for trauma resuscitation. Maternal resuscitation is the best fetal resuscitation. Manage the airway, ensure adequate ventilation, and provide supplemental oxygen. Place a nasogastric tube early, because delayed stomach emptying and diminished lower esophageal sphincter tone increase the risk of aspiration of gastric contents. Keep the patient in the semi-left lateral decubitus position to the extent possible to minimize vena caval compression. Identify and control sources of hemorrhage since maternal blood loss and hypovolemia exacerbate fetal hypoperfusion. Increase crystalloid infusions by 50% to account for the patient's additional plasma volume. Do not administer vasopressors until volume and blood are replaced to minimize risk of uteroplacental hypoperfusion. If vasopressors are needed for maternal resuscitation, however, do not restrict their use (see chapter 25 for further discussion).

Table 256-1 summarizes critical ED interventions for trauma in pregnancy. Do not withhold critical maternal interventions or diagnostic procedures out of concern for potential adverse fetal consequences.

Administer Rho(D) immunoglobulin to Rh-negative pregnant women with abdominal trauma. Two dose options are acceptable: 50 micrograms IM for gestation of ≤12 weeks and 300 micrograms IM for gestation of ≥13 weeks, or 300 micrograms IM for all gestational ages. The rationale for the lower dose for ≤12 weeks gestation is that the total fetal blood volume at 12 weeks gestation is about 4.2 μL, and a 50-microgram dose is effective for up to 5 μL of fetomaternal hemorrhage. A 300-microgram dose will protect for up to 30 μL of fetomaternal hemorrhage. The obstetrician can best determine if doses of >300 micrograms should be administered. Because the 72-hour window for Rho(D) immunoglobulin therapy established for postpartum administration has been extrapolated to apply after abdominal trauma, serial fetomaternal hemorrhage testing may be performed in the hospital.^7,13

Provide tetanus prophylaxis as needed. Although tetanus toxoid is a category C drug for all trimesters of pregnancy, it is commonly accepted as safe. Tetanus antibody crosses the placenta, so it can also reduce the incidence of neonatal tetanus.

Continue to carefully monitor fetal heart rate patterns and frequent uterine contractions with cardiotochodynamometry. If fetal distress develops, consult obstetrics if not already at the bedside. Treat maternal hypovolemia, hemorrhage, and hypoxia and continue assessment for placental abruption. In a viable gestation, the presence of fetal tachycardia, lack of beat-to-beat or long-term variability, or late decelerations on tocodynamometry indicate fetal distress and may be indications for emergency cesarean delivery.⁶

A minimum of 4 to 6 hours of external tocodynamometric monitoring of the potentially viable fetus appears sufficient to predict immediate adverse pregnancy outcomes and is indicated for all pregnant patients evaluated for trauma, even those without obvious abdominal injury. In patients demonstrating persistent contractions or uterine irritability, extend tocodynamometry to a minimum of 24 hours. Although no uniform standards exist, many obstetricians believe that patients with fewer than three contractions per hour during an initial 4-hour observation period can be safely discharged.

LAPAROTOMY

The indications for emergent laparotomy in the management of pregnant trauma patients remain unchanged from those for nonpregnant patients. The fetus appears to tolerate surgery and anesthesia well if adequate oxygenation and uterine perfusion are maintained. Do not withhold surgery out of concern for fetal compromise. Emergency cesarean delivery in the setting of trauma results in a fetal survival rate as high as 75% when gestation is ≥26 weeks, fetal heart tones are present on admission, and the procedure is performed at the earliest indication of fetal distress (see "Perimortem Cesarean Section" in chapter 25).¹⁴

Disposition of a pregnant trauma patient after the emergency assessment and management is based on the nature and severity of presenting injuries and the gestational length of the pregnancy. Manage patients with multisystem trauma or with minor but potentially serious injuries jointly with trauma surgeons and obstetricians. Women at ≥20 weeks of gestation require observation or admission for fetal monitoring. If there is evidence of fetal distress or uterine irritability during the initial assessment, then immediately consult an obstetrician. When the patient needs transfer to other facilities for definitive care, stabilize the patient's condition as much as possible prior to transfer, with provisions for an appropriate level of care during transport. Adhere to transfer policies that comply with federal regulations. If the patient can be discharged, ensure adequate follow-up obstetrical care.¹⁵

AUTOMOBILE RESTRAINT

Motor vehicle seat belt use during pregnancy helps protect both the mother and the fetus, and pregnant drivers and passengers should wear safety belts throughout pregnancy. The best predictors of fetal loss or adverse outcome are crash severity and lack of, or improper use of, seat belts.¹⁶ The lap belt should be placed as low as possible under the gravid uterus (across both the anterior superior iliac spines and the pubic symphysis), and the shoulder harness should be positioned snugly between the breasts but off to the side of the uterus.^17,18 Pregnant women should use both seat belts and air bags. Do not disconnect air bags for pregnant women.¹⁷ Although there is a risk of injury to the more proximally located gravid uterus, as long as the pregnant woman is properly seated and uses properly placed seat belts, the benefits of air bags appear to outweigh the risks.¹⁹

INTERPERSONAL VIOLENCE

Assaults are the third most common mechanism of injury for pregnant women after falls and motor vehicle crashes.³ To screen for the possibility of interpersonal violence, encourage a social services evaluation or referral in all but the most obvious cases of accidental injury (Table 256-2).¹