Pregnancy Trauma

Etiology

The etiology of trauma in pregnancy may be multifactorial. The physics of the growing abdomen results in an imbalance, which increases the frequency of maternal falls from standing or from height, such as stairs. Further, the clinician must maintain a heightened suspicion for non-accidental causes, either self-inflicted or other. Domestic violence increases during pregnancy, placing the mother and the fetus at obvious risk for injury. Domestic violence occurs in 4% to 8% of pregnancies and is associated with a 5% risk of fetal death.

The normal physiology of the pregnant mother complicates the evaluation and management of trauma in pregnancy. The gravid uterus is particularly susceptible to penetrating and blunt force trauma to the abdomen. Motor vehicle accidents account for 50% of all traumatic injuries during pregnancy and 82% of trauma-related fetal death. The main reason for this equates to the improper use of seat belts. The lap belt must be placed under the dome of the abdomen and across the pelvis to reduce pressure on the uterus during a motor vehicle collision. The shoulder harness should lay across the clavicle and between the breasts.[3][4]

Epidemiology

Trauma is sustained in 8% of all pregnancies. Regardless of the mechanism, trauma can be life-threatening for both the mother and fetus. Rapid evaluation and treatment of the mother in trauma should be even further heightened, as maternal shock is associated with an 80% fetal mortality. Pelvic fracture is the most common maternal injury that results in fetal death. Data from a review of pregnant women with sustained pelvic fracture by Leggon et al showed the rate of fetal mortality was 35%. Causes of death included direct fetal injury (20%), placental abruption (32%), and maternal shock (36%). Dilated vasculature, due in part to maternal physiologic changes, places mothers at increased risk for hemorrhage following pelvic fractures, with mortality in these mothers being as high as 9%.

The most devastating injuries following direct, blunt trauma include placental abruption and uterine rupture. Abruption is thought to complicate 1% to 6% of minor injuries and up to 50% of major injuries. Uterine rupture is overall rare, occurring in less than 1% of patients who are pregnant with trauma, and is most commonly associated with direct impact with sustained force to a previously scarred uterus. In contrast to blunt trauma, maternal mortality is more favorable following penetrating injury, as the gravid uterus serves as protection for the maternal internal organs. Conversely, fetal mortality following penetrating injury has been reported to be as high as 73%.[5][6]

Pathophysiology

Anatomic and Physiologic Changes in Pregnancy

To recognize abnormal vital signs and injuries in a pregnant individual, normal anatomic and physiologic changes in pregnancy must be understood. Multiple organ systems change during pregnancy; the major, pertinent systems are discussed herein.[7][8]

Abdominal Changes

The tone of the lower esophageal and gastric motility is reduced in pregnancy. This leads to reflux and retained food contents in the stomach, respectively. Because of these factors, there is an increased risk of aspiration, especially during intubation. The peritoneum stretches markedly and becomes much less sensitive to peritoneal irritation by the third trimester. Even patients with traumatic hemoperitoneum may not exhibit abdominal tenderness on examination due to the peritoneal stretching and insensitivity. The uterus eventually becomes the largest intraabdominal organ. The uterine walls become thin and susceptible to injury. Bloononpregnantases from a nonpregnant state of 60 mL/min to an impressive 600 mL/min at term. As in the typical blunt trauma patient, the spleen remains the most commonly injured organ.

Hematologic Changes

Plasma volume and the red cell mass increase throughout pregnancy. Plasma volume doubles by the end of the third trimester; however, it is in much higher proportion than the red blood cell mass increase, resulting in dilutional anemia during pregnancy. The normal hemoglobin is 10 to 14 grams per deciliter by the term. The liver becomes hypermetabolic, increasing the production of coagulation factors and fibrinogen. With this production, the patient is more at risk for deep vein thrombosis and disseminated intravascular coagulation (DIC). DIC panels must be interpreted with caution. Because it is expected to have elevated fibrinogen levels at term, a normal fibrinogen level may indicate DIC.

Pulmonary Changes

Respiratory rate (RR) x tidal volume (TV)= minute ventilation (MV). RR does not change during pregnancy. Counterintuitively, TV has increased by 40%, leading to a 40% increase in MV. This leads to a lowered partial pressure of carbon dioxide of 30 mm Hg (normal values are 35-45 mm Hg), resulting in a chronically compensated respiratory alkalosis. This must be taken into account when evaluating a blood gas. The diaphragm is elevated by approximately 2 to 4 cm at term. This is essential to know when performing a tube thoracostomy. Chest tubes should be placed in the same mid-axillary line, however, 2 cm higher to avoid potential puncture into the liver or spleen. Lastly, the Mallampati score, an airway assessment score used prior to intubation, is an estimated distance from the base of the tongue to the roof of the mouth. Mallampati classification ranges from 1 to 4: 1 denotes all inner oral cavity structures visible, to 4, wherein only the hard palate is visible. The Mallampati score increases throughout pregnancy, leading to a greater percentage of levels 3 and 4. Given all of these pulmonary changes, a pregnant trauma has the potential to result in a difficult airway scenario.

Cardiovascular Changes

Pregnancy-related cardiovascular changes require careful interpretation of the vital signs in the trauma patient. Pulse in the third trimester elevates 15 to 20 beats per minute. The blood pressure decreases by 15 to 20 mm Hg but returns to normal during the third trimester. Any sign of hypotension should be evaluated immediately, given this return to the normal level; this should not be attributed to the pregnant state as this is an interpretation of exclusion in the setting of trauma. Finally, as noted previously, the plasma volume rises by 50%, thus leading to a potentially delayed recognition of shock. By the time the maternal blood pressure falls, the patient may have already sustained a 30% blood loss.

Pregnancy-Related Injuries

As with any trauma, certain injury patterns are likely. In addition, there are injuries unique to pregnancy that must be considered.

Premature labor

Premature labor is defined as uterine contractions occurring at less than 36 weeks gestation (premature) accompanied by cervical changes (labor). Although patients with trauma may feel pain similar to real labor contractions, these pains may not represent contractions. Toconometry is indicated to determine if the contractions are real. The most common cause is placental abruption (see below). If contractions are present, the diagnosis of placental abruption must be considered and investigated, as well as uterine rupture and other hemorrhages. If present, correction of hypoxia and hypovolemia should occur as these are common causes of premature labor.

Placental abruption

Placental abruption is the leading cause of fetal death not related to maternal death and occurs in 1% to 5% of minor trauma cases. The classic triad of vaginal bleeding, abdominal pain, and uterine irritability may not be present. The edges of the placenta may encase the bleeding internally, and the peritoneum may be markedly insensitive given the massive stretching in the near term. Ultrasound may be helpful in the diagnosis but is not sensitive; the diagnosis is not ruled out if the ultrasound does not reveal abruption. Regardless, toconometry is required for a minimum 4 hours and may be extended by the obstetrical team for many reasons.

Amniotic fluid embolus

The pathophysiology of amniotic fluid embolus, which is uncommon and catastrophic, is currently poorly understood. The patient may present much like a massive pulmonary thrombotic embolus. There is no specific treatment for this entity except supportive care, intubation, vasopressors, and transfusion.

Uterine rupture

Although a rare complication of trauma (0.06%), fetal mortality approaches 100% when present and most often occurs in the third trimester. Because of the high amount of force required to cause uterine rupture, it is commonly associated with pelvic fractures and bladder injuries. The classic presentation is dramatic, with abdominal pain and distention (due to the unfolding of the fetus). However, given the peritoneum's insensitivity in the third trimester, no pain may be present. A high index of suspicion accompanied by prompt recognition is critical. Treatment is exploratory laparotomy, delivery of the fetus, and supportive care.

History and Physical

The standard trauma algorithm should be followed when evaluating a pregnant individual who has experienced trauma. Trauma assessment includes a primary, secondary, and tertiary survey. Attention should be paid to the vital signs as they change throughout normal pregnancy, noting changes to physiology as described previously. If alert and able, all women of childbearing age involved in trauma should be questioned on the feasibility of pregnancy, and beta-human chorionic gonadotropin testing should be obtained unless they expressed an interest to conceive. Prior history of preterm labor, placental abruption, and placenta previa are also important to illicit if able. Likewise, urgent obstetrics and gynecology consultation is recommended, especially when the patient is in the second or third trimester. When the airway is compromised or rapid sequence intubation is deemed necessary, lower doses of succinylcholine are required due to the lower concentrations of pseudocholinesterase during pregnancy. Avoiding hypotension and providing supplemental oxygen due to the significant fetal vulnerability to hypoxia is essential.

Clinical assessment alone may identify potential injury to the uterus or fetus. Concerning findings include:

• Penetrating injury to the abdomen
• Vaginal bleeding
• Ruptured membranes
• Bulging perineum
• Presence of contractions
• Abnormal fetal heart rate or rhythm

Vaginal bleeding is abnormal before labor and can be indicative of placental abruption, early labor, premature cervical dilation, or placenta previa. Rupture of the amniotic sac should be suspected when there is cloudy, white, or green discharge, which leads to an increased risk of infection. A ruptured amniotic sac may also lead to umbilical cord prolapse, which itself is an obstetric emergency requiring immediate cesarean section. If hemodynamically able, the pelvic examination should, therefore, include a speculum exam.

In addition, the abdomen should be palpated to determine the level of uterine height. Measurement of fundal height allows gestational age estimation, which may be the only insight into gestational age in a patient who is unresponsive. Between 8 to 12 weeks, the uterus begins to enter the abdominal cavity, arising above the pubic symphysis. At 20 weeks, the uterus should grow at approximately 1 finger’s breadth until 40 weeks of gestation. The uterus reaches the sternum at 36 weeks and then becomes lower as the fetal head engages into the pelvis. The discrepancy between the fundal height and known gestational age should alert the clinician to an abnormality concerning uterine trauma or a preexisting condition such as multiple pregnancies or intrauterine growth retardation.

Evaluation

Again, standard advanced trauma life support (ATLS) algorithm and protocol should guide evaluation and resuscitation in the patient who happens to be pregnant. Fetal heart tones can be auscultated with a stethoscope at 20 weeks gestation; before this, a Doppler is needed. Evaluation of the fetus itself is best performed with tonometry, which is the most accurate means to detect fetal distress. Fetal heart tones can be detected as early as 12 weeks of gestation, usually between 110 and 160 beats per minute (bpm). Initially, fetal hypoxia manifests as tachycardia, but as the arterial oxygen content decreases, the fetus ultimately becomes bradycardic. Therefore, any sustained rate below 120 bpm should be recognized as fetal distress. If fetal distress is detected, then maternal blood loss must be suspected. Monitoring fetal heart rate should be initiated on any woman more significant than 24 weeks gestation and is typically recommended for 4 to 6 hours after the initial presentation.

Radiographic imaging is often indicated, especially in those who have sustained traumatic events. However, due to the fear of potential teratogenic and harmful effects of ionizing radiation, clinicians are often hesitant to order appropriate studies. The fear of radiation exposure should not take precedence over quickly establishing the correct diagnosis to allow the treatment initiation. In trauma, as in all other scenarios, the care of the patient, not the fetus, should take priority and take precedence over the risk of ionizing radiation. The effects of radiation exposure on the fetus depend on the gestational age and the amount of radiation. In general, the earlier the gestational age, the higher the risk. Specifically, abdominal x-rays submit 200 mrad (0.1 to 0.3 rads) of ionizing radiation to the fetus, while abdominal and pelvic computer tomography scans subject the fetus to 3 to 4 rads. The accepted accumulated dose of ionizing radiation during pregnancy is less than 10 rads, with no single diagnostic study exceeding 5 rads.

Between 8 to 15 weeks gestation, high-dose radiation (>10 rads) may lead to intra-uterine growth retardation and central nervous defects. Beyond 15 weeks, there appear to be no dose-dependent effects such as fetal loss or congenital defects. Stochastic effects, such as the subsequent risk of cancer or leukemia, are increased with exposure of 1 rad or more. The rate of such effect is approximately 1 for every 500 high-dose exposures. Efforts should be taken to decrease unnecessary scans, reduce the overlap of body sections, and avoid multiple passes when possible.

The risk of a missed injury or delay in diagnosis is much greater for the fetus than the risk of radiation. As such, the American College of Obstetricians and Gynecologists has submitted the below guidelines for diagnostic imaging during pregnancy:

• Women should be counseled that x-ray exposure from a single diagnostic procedure does not result in harmful fetal effects. Specifically, exposure to less than 5 rads has not been associated with an increase in fetal anomalies or pregnancy loss.
• Concern about the possible effects of high-dose ionizing radiation exposure should not prevent medically indicated diagnostic x-ray procedures from being performed on a pregnant woman. Other imaging procedures not associated with ionizing radiation (eg, ultrasonography and magnetic resonance imaging [MRI]) should be considered when appropriate during pregnancy.
• Ultrasonography and MRI are not associated with known adverse fetal effects.
• Consultation with an expert in dosimetry calculation may help calculate the estimated fetal dose when multiple diagnostic x-rays are performed on a pregnant individual.
• The use of radioactive isotopes of iodine is contraindicated for therapeutic use during pregnancy.
• Radiopaque and paramagnetic contrast agents are unlikely to cause harm. They may be of diagnostic benefit, but these agents should be used during pregnancy only if the potential benefit justifies the potential risk to the fetus.

Adjunct imaging modalities include ultrasonography and magnetic resonance imaging. Ultrasound in extended focused abdominal sonography in trauma (eFAST) should still be incorporated during the trauma secondary survey. Results from a retrospective cohort of more than 2300 FAST exams show that the sensitivity and specificity show differences between the detection of free fluid in those who are pregnant and those who are not. As in another trauma scenario, this tool allows the potential rapid identification of hemopneumothorax, pericardial tamponade, and fluid in the Morrison pouch or the splenorenal recess. However, isolated pelvic free fluid detected by ultrasound is of unclear clinical significance in the pregnant patient. MRI is considered a good imaging modality in pregnancy due to its lack of ionizing radiation and specificity; however, its use in the emergent setting is limited by availability and timely duration, making its use in patients with trauma often nonpractical.[9][10]

Treatment / Management

ATLS principles remain the same whether the patient is non-gravid or full-term. As always, taking care of the patient, in turn, takes care of the fetus. The best early treatment of the fetus is the optimal resuscitation of the mother. Upon determining gravidity, consultation with obstetrics is critical—nearly all women who are patients aged between 10 and 55 years old warrant beta-human chorionic gonadotropin testing. Transfer to an appropriate trauma center with applicable obstetrical specialized care has demonstrated improved maternal and neonatal outcomes post-injury as opposed to nontrauma centers. The positioning of the patient to avoid or alleviate aortocaval compression syndrome, also known as a supine hypotensive syndrome, may be necessary. Women in the second and third trimesters should thus be placed onto their left side with a 15-degree bump or roll behind them for support to assist in displacing the uterus from vena cava compression, increasing venous return and thus cardiac output.

The patient's Rhesus (Rh) blood type should be sought. If maternal negative, there is a chance of developing iso-immunization and compromising further pregnancies. Rh immunoglobulin (eg, RhoGham) should be administered regardless of mechanism, including falling from standing, as maternal Rh sensitization occurs at 0.01 to 0.03 mL in 70% of patients who are Rh-negative. The dose of RhiImmunoglobulin is dependent upon the gestational age. At less than 12 weeks gestational age, 150 mcg is indicated. At greater than 12 weeks, 300 mcg is indicated. The amount needs to be increased if the feto-maternal hemorrhage is marked in massive blunt-force abdominal trauma. The Klei-Hauer Betke test determines this; this test is an acid elution assay on blood. After lysing cells with acid, the amount of fetal blood in the maternal system is shown. This test has a 5 mL maternal-fetal hemorrhage threshold, but iso-immunization can occur at 0.01 mL. Therefore, this test should be utilized to determine not only if but also how much additional Rh immunoglobulin is required. 

Maternal vital signs are less sensitive; therefore, if hypotension is present, immediate investigation and treatment must ensue. In cases of hypovolemic shock, the mother shunts blood from her fetus. Further, the placenta is highly sensitive to catecholamines and vasopressors alike. Early aggressive intravascular repletion and volume resuscitation are thus paramount, and permissive hypotension should be avoided in this population.

Similarly, vasopressors should be used with the knowledge that this further compromises placental blood flow. Similar to the nonpregnant woman, blood product resuscitation should proceed with a 1:1:1 component ratio. In instances of severe hemorrhage within 3 hours from trauma, tranexamic acid is deemed safe and should likewise be used. For those who require urgent central venous access, femoral catheters should be avoided when able, again due to potential uterine compression of the vena cava reducing venous return. Special consideration should also be given to those requiring thoracostomy tube placement. In later terms of pregnancy, the diaphragm may rise to an additional 4 cm. Thus, the inserting clinician should plan on an insertion site of 1 to 2 intercostal spaces higher than traditional placement to avoid intra-abdominal issues for exploratory laparotomy, the same in the pregnant individual as in the nonpregnant trauma individual. However, it is important to note that laparotomy alone is not an indication for cesarean section. During laparotomy, the uterus should be handled with care, being careful not to twist or place excess traction, as this may lead to potential vascular compromise. With adequate resuscitation, the fetus should tolerate the operative procedure well. With this being said, an obstetric clinician should be readily available and pretermat the time of exploration.

Nearly 25% of patients with trauma with viable fetuses may have preterm labor and almost 40% experience contractions. Preterm labor, in general, should be treated with standard obstetric protocol. Next to maternal death, placental abruption is the next most common cause of fetal death. Nonreassuring fetal heart tones with clinical evidence concerning placental abruption warrants emergent cesarean section. In addition to placental abruption, severe pelvic or spine fractures, fetal malposition with premature labor, maternal disseminated intravascular coagulation, and gravid uterus when interfering with exposure of potential injuries/exposure during laparotomy are all indications for emergent cesarean section. The uterus is exposed through midline vertical celiotomy. The uterus itself is incised vertically with scissors, exposing the infant's head with immediate suction of the oropharynx as the infant is delivered. The umbilical cord is subsequently clamped and divided. The placenta is manually removed, and the endometrium is inspected to ensure no retained membrane is present. The uterus is then closed in layers with a running absorbable stitch. Oxytocin (Pitocin) may be administered for post-partum bleeding.

Special Consideration: 

• Tetanus toxoid is safe to administer during pregnancy.
• Standard antibiotic prophylaxis can be used; however, due to teratogenic potential, aminoglycosides, quinolones, metronidazole, and sulfonamides should be avoided.
• Enoxaparin or heparin may be used for inpatient pharmacologic venous-thrombo-embolic prophylaxis as it does not cross the placenta.
• Further medication guidelines for the treatment of the pregnant patient may be obtained at www.cdc.gov/pregnancy/meds/treatingfortwo/index.html.
• Peri-mortem cesarean delivery can be performed with a fetus that is at least 25 weeks gestation if within 15 minutes between maternal death and delivery. Maternal cardiopulmonary resuscitation should be continued in conjunction with acute coronary syndrome protocol to allow immediate neonatal support and delivery to occur within 4 minutes of maternal death. 

Differential Diagnosis

The differential diagnosis for pregnancy trauma includes the following:

• Blunt abdominal trauma
• Emergent management of abruptio placentae 
• Penetrating abdominal trauma

Complications

The following complications may occur from trauma during pregnancy:

• Exsanguination
• Uterine rupture
• Retroperitoneal hemorrhage
• Rupture of amniotic membrane
• Amniotic fluid embolism
• Placental abruption