1.   Pregnancy workup. Maternal pelvic examination should include abdominal palpation of the uterus for assessing uterine tone, fundal height, fetal position, and sterile speculum examination to determine if there is blood or amniotic fluid leakage. Advanced trauma life support (ATLS) guidelines advocate routine vaginal examination. Exclusion of placenta previa by ultrasound should precede vaginal examination because of the increased risk of inducing hemorrhage. In cases of mild maternal injury, clinical judgment has a role in determining the need to conduct vaginal examination. Fetal condition should be monitored only if the gestational age exceeds the limit of fetal viability. Information regarding gestational age can be received from the medical file or through physical examination; the uterine fundus is palpable above the pubic crest from the second trimester of gestation onward. Recurrent uterine contractions suggest premature labor if accompanied by cervical change. Excess uterine activity (>4 contractions per hour) without cervical change suggests either placental abruption or premature labor. A nonreassuring fetal heart rate should always alert the clinician to the likelihood of undiagnosed maternal injury; maternal hypotension causes uterine and fetal hypoperfusion resulting in nonreassuring fetal heart rate status.

2.   Assessment and implications of fetal viability. Gestational age and fetal condition should be considered when determining the need for fetal monitoring, when considering administration of steroids to promote fetal lung maturation, and when deliberating delivery after initial maternal stabilization. Ethical dilemmas surrounding the management of neonates of borderline viability are more commonly discussed in the delivery room than in the trauma unit. However, the principles guiding care are the same: respect toward parental opinions, which may differ from those of the treating staff, placement of greater emphasis on fetal/neonatal condition than on gestational age after 24 weeks gestational age, and understanding that impairment does not necessarily equal poor quality of life.³¹ Premature delivery occurring at a gestational age of less than 22 weeks will likely culminate in fetal death. Should delivery occur at this stage, there may be a strong preference for neonatal comfort care. When maternal trauma occurs at a gestational age exceeding 24 weeks, there may be a significantly greater inclination to maximize the efforts invested in the neonate and to perform full neonatal resuscitation.³² Regardless of gestational age, maternal treatment should remain guided by maternal, rather than fetal, condition. Optimizing maternal condition will also increase the likelihood of ongoing pregnancy.

Delivery must be considered in an initially unstable patient only if maternal instability results from a complication of the pregnancy itself (e.g., hemorrhage from placental abruption). Alternatively, delivery may be considered if a potentially viable fetus (i.e., gestational age >24 weeks) shows unresolving or intermittent signs of distress despite maternal stability, provided that delivery will not compromise the mother. Otherwise, the intrauterine environment is optimal for the fetus. Antenatal steroids may be administered if there is ongoing discussion regarding the option of early delivery. A recent Cochrane database review concluded that “it remains unclear whether one corticosteroid [or one particular regimen] has advantages over another. Dexamethasone may have some benefits compared with betamethasone such as less intraventricular hemorrhage . . . ”³³ The evidence for administration of vitamin D is experimental at best,³⁴ and there is insufficient evidence to support administration of ambroxol.³⁵

        IV.Limitations in assessing severity of maternal injury

A.Severity of injury. Severity of injury in nonpregnant trauma patients is commonly standardized by the use of trauma scores. The ISS,³⁶ new injury severity score (NISS),³⁷ and the trauma and injury severity score (TRISS)³⁸ are the most commonly used scoring methods.³⁹ Although uterine rupture is rare in the pregnant trauma victim, severe maternal injury may be associated with a significantly increased risk of placental abruption. Both are potentially life-endangering injuries. Placental abruption has been associated with maternal mortality exceeding 50%,⁴⁰ yet no trauma score contains any reference to obstetric injury.

B. Advanced trauma life support training and use of vital signs. ATLS training advocates use of vital signs (blood pressure, heart rate, and respiratory rate) for clinical grading of shock severity. The validity of this classification has been called to question in the normal adult population^41,42 and should be used even more critically in the pregnant patient.

C. Implications of the physiologic changes of pregnancy. Cardiac and pulmonary physiology undergo significant changes throughout pregnancy; lowering of maternal peripheral vascular resistance leads to a 5 to 10 mm Hg decrease in brachial systolic blood pressure occurring from early pregnancy onward, as well as a 5 to 25 beats per minute (bpm) increase in heart rate by the third trimester.⁴³ Pregnancy-induced effects on the chemoreflex respiratory drive promote an increase in respiratory rate, creating a physiologic state of hypocapnea.⁴⁴ Although there is an overall 40% increase in total blood volume, cardiac output increases by 0.5 to 1.5 L per minute by the second trimester,⁴³ rendering tolerance to hemorrhage unpredictable.

The increase in blood volume is not accompanied by an increase in red blood cell production, resulting in a physiologic decrease in hematocrit commonly observed in pregnant women.⁴⁵ Furthermore, anemia is a common nutritional disorder in pregnancy worldwide.^46,47 Thus, baseline hemoglobin levels below 11.0 mg per dL have been observed in up to 50% of pregnant patients in some studies.⁴⁸ Conversely, pregnancy is accompanied by a hypercoagulable state⁴⁹ and an increase in plasma fibrinogen concentration,⁵⁰ both of which may be protective during acute hemorrhage.

D.Clinical assessment of patient severity. The first publications noting inadequate tools for the clinical assessment of injury severity in the pregnant population were the United Kingdom Confidential Enquiries into Maternal and Child Health (CEMACH)^51,52 reports. In 2007, Swanton et al.⁵³ surveyed 71% of the lead obstetric UK anesthetists who responded on behalf of their maternity units (158 out of 222). Although almost all of the surveyed UK hospitals (96%) were using early warning scores at this time, less than a quarter of the rezspondents (23%) considered nonobstetric scores relevant to obstetric physiology. Despite this, only 19% were using an obstetric early warning score.⁵³ In an attempt to address this issue, Carle et al.⁵⁴ published a landmark paper in 2013, which described the use of physiologic variables collected during the first 24 hours of critical care obstetric admissions to derive a weighed obstetric early warning score. Complex data regarding ventilation and level of consciousness were simplified to adapt the score to the reduced monitoring capabilities of clinical settings in which pregnant women were treated. The paper included a derivation cohort of 2,240 and a validation cohort of 2,200 obstetric admissions. The authors achieved an area under the receiver operating characteristic curve of 0.995 (95% confidence interval [CI], 0.992 to 0.998) for the statistical score and 0.957 (95% CI, 0.923 to 0.991) for the clinical score, demonstrating that clinical scores are capable of discriminating obstetric survivors from nonsurvivors.⁵⁴ Within 7 years, a repeat UK survey generating a response rate of 63% (130 per 205) demonstrated use of obstetric early warning scores in all of the responding maternity units.⁵⁵ Although considerable data suggest that standard (in this case, ATLS) shock categories may be inadequate for classifying the severity of obstetric hemorrhage, similar analyses of obstetric trauma data are still sorely missing.

         V.Principles of radiologic assessment

Radiologic imaging remains a mainstay of trauma care. Clinicians often hesitate to order imaging studies for the pregnant patient because of concern regarding the long-term effects of imaging on fetal development and uncertainty regarding the impact of pregnancy on test sensitivity. The fact that pregnant women are more likely to sustain severe abdominal injuries than the general adult population⁵⁶ creates a dilemma for the treating staff. One must always consider whether potential maternal benefit outweighs the potential risk to the fetus when choosing to perform imaging studies in maternal trauma. However, there is no justification for refraining from testing when clinically indicated.

A. Ultrasound imaging. Ultrasound imaging does not require the use of ionizing radiation or contrast media. Thus, it is the imaging mode of choice for pregnant women. Although laboratory studies suggest that diagnostic levels of ultrasound can affect human tissue,^57,58 no adverse fetal effects have been associated with the use of diagnostic ultrasound imaging in humans. B-mode, M-mode, and 3D ultrasound imaging are not expected to result in harmful fetal biologic effects. Conversely, Doppler imaging requires high energy levels and focusing of the ultrasound beam at a specific position for a prolonged period of time. The International Society of Ultrasound in Obstetrics and Gynecology has issued specific recommendations for the use of Doppler imaging in pregnancy, including avoidance of pulsed Doppler imaging in the first trimester whenever possible and use of minimal exposure times with a displayed thermal index of 1.0 or less.⁵⁹

1.   Focused assessment with sonography for trauma (FAST) has not been studied adequately for diagnosing nonpregnancy-related injuries in the pregnant trauma patient.⁶⁰ Although this test is often perceived to have sensitivity and specificity similar to that observed in nonpregnant trauma patients,⁶¹ particularly in severe injury,⁶² few clinicians are capable of detecting free intraperitoneal fluid volumes smaller than 400 mL in this population. The mean amount of detectable fluid usually exceeds 600 mL.⁶³ The likelihood of a false negative study in the presence of an intraabdominal amount of fluid exceeding a tenth of the total adult blood volume should serve to caution that an initial negative examination does not rule out the presence of intraabdominal injury.⁶¹ Even when peritoneal fluid is detected in this patient population, its clinical significance has been questioned. Early studies noted that the presence of free fluid may be physiologic in female patients of reproductive age who have undergone trauma, provided it is isolated to the cul-de-sac.⁶⁴ This determination has recently been refuted in a study showing that <10% of pregnant patients without antecedent trauma have free pelvic fluid.⁶⁵ Despite this, many authors recommend a FAST examination to evaluate for free peritoneal fluid as a first-line diagnostic examination in pregnant women who have sustained blunt trauma.^{2,4,13,30,56,60} Regardless, ultrasound imaging in the traumatized pregnant patient is no substitute for CT examination; it is a significantly inferior imaging modality in terms of injury detection.^66,67

2.   Fetal ultrasound can diagnose major fetal damage, such as brain injury and decapitation in the setting of trauma.^68,69 Regardless of time elapsing from the injury, fetal ultrasound is indicated as a diagnostic adjunct when a nonreassuring fetal status is observed during external fetal monitoring.

3.   Placental abruption and uterine rupture, the two pregnancy-related injuries that are of the greatest concern for maternal well-being, are not easily diagnosed by ultrasound imaging. The likelihood of a missed diagnosis of placental abruption is very high (up to 80%), even in pregnant women who have not sustained trauma,^70,71 and there has been no systematic study of the accuracy of ultrasonography for diagnosing this specific injury in trauma. The diagnosis of uterine rupture can be made in the presence of abnormal findings, such as an empty uterus surrounded by echogenic intraabdominal fluid (which is compatible with hemoperitoneum).⁷²

B. Standard radiology and computed tomography scanning. Standard radiology tests are considerably less informative than CT imaging. CT imaging thus constitutes “the imaging study of choice for narrowing the differential diagnosis and optimizing management of the clinical condition.”⁷³

1.   Fetal risk

a.   Imaging tests involving radiation may be divided into three groups based on the degree of fetal exposure: low, medium, and high. Cervical spine and extremity radiography are considered low exposure tests because they rarely require more than 0.001 mGy. Chest radiography, which also belongs to this group, requires up to 0.01 mGy. CT imaging of the chest belongs in the lower range of the medium exposure group. This test requires up to 0.66 mGy. Contrary to these less controversial tests, lumbar spine imaging and CT imaging of the head or neck may require up to 10 mGy, which exceeds the recommended dose for non–life-threatening situations. Abdominal and pelvic CT belong to the high exposure group—these tests may require up to 35 and 50 mGy, respectively.⁷³

b.   The risk of fetal teratogenesis following exposure to radiation is greatest during the first trimester of pregnancy.⁷⁴ Intrauterine exposure to radiation has also been associated with an increased risk of childhood cancer, but the precise level of risk at low doses of exposure remains unknown.⁷⁵ A typical radiologic workup requires <50 mGy. Although this amount of radiation may be associated with an increased risk of childhood cancer, in absolute terms, the overall risk remains low (1:250).⁷³ In the past, concerns have also been raised that in utero exposure to iodinated contrast agents may be associated with an increased risk of fetal hypothyroidism. However, recent studies have not confirmed this suspicion.^76–79

2.   Computed tomography imaging. CT imaging remains the imaging of choice for diagnosis of traumatic maternal injury.

a.   Diagnosis of head, spinal, and chest injuries is unaffected by pregnancy. Abdominal and pelvic findings may be detected despite pregnancy, but the radiologist must be aware of the physiologic changes typically occurring from the second semester of pregnancy onward. These may include widening of the sacroiliac joints and pubic symphysis, hydronephrosis, ovarian vein enlargement, and inferior vena cava compression.⁸⁰

b.   CT imaging is also an excellent tool for diagnosing placental abruption, impending abortion, and uterine rupture. The accuracy of this imaging modality for diagnosing placental abruption may be as high as 96%, with a sensitivity of 86% to 100% and a specificity of 80% to 98%. Although CT imaging is not used routinely for these indications, if performed for other maternal reasons, evaluation should include surveillance for placental abruption and uterine rupture^81,82 because these injuries can easily be overlooked.⁸² Decreased placental enhancement on CT imaging is a strong indicator of placental abruption.^83,84 CT indicators of impending abortion include the presence of low-lying products of conception, products of conception in the cervix, and blood in the cervix or vagina.⁸⁵ Indicators of uterine rupture include a through-and-through uterine wall defect, extrauterine fetal location, and the presence of hemoperitoneum.^85–87

C. Magnetic resonance imaging. The general recommendation regarding magnetic resonance imaging (MRI) is to avoid use of this imaging mode during the first trimester of pregnancy unless the test result will determine maternal treatment. Although exposure in the first trimester has not been associated with long-term fetal sequelae, this may stem from an insufficient amount of data concerning fetal exposure. During the second and third trimesters, performance of an MRI does not increase the risk of the fetus provided the dose remains <3.0 T. Experimental studies suggest that gadolinium contrast agents do cross the placental barrier, but this does not constitute a contraindication to use of these agents.⁸⁸ MRI is probably still underutilized in trauma for three main reasons: the test is costly, time consuming, and requires specialized monitoring techniques and equipment.⁸⁹ This imaging technique is well suited to detect placental trauma because of the ability to improve tissue contrast by adapting the pulse sequences and parameters and because it provides several imaging planes in parallel.⁹⁰ Excellent interobserver agreement has been shown for MRI diagnosis of placental abruption.⁹¹ MRI may also provide important information regarding the presence and severity of fetal brain injury.⁹²

        VI.Clinical and test findings versus pregnancy outcome

A. Prenatal maternal injury. Prenatal maternal injury is associated with an increased risk of adverse pregnancy outcome.^14,15 Among the clinical predictors studied for their association with a poor pregnancy outcome, lack of maternal belting in motor vehicles is consistently cited.^93,94 One study found that unbelted pregnant women were almost three times more likely to experience fetal death than belted pregnant women.¹ Severe maternal injury has also been associated with a significantly increased risk of placental abruption, uterine rupture, and preterm labor, particularly in the third trimester.⁷ A maternal ISS exceeding 25 has been associated with a 50% risk of fetal death,⁴⁰ and maternal shock also constitutes an important predictor of fetal demise.^40,95,96 Maternal pelvic fractures and loss of consciousness, both of which contribute to a high ISS, have been shown to be independent risk factors for adverse pregnancy outcome.^12,96

B. Minor injuries. Minor injuries considered less significant for the general population may not be minor in the setting of pregnancy. Fractures, dislocations, sprains, and strains are the most common type of injury observed in pregnancy.¹⁴ Yet, minor injuries and injuries away from the trunk may also lead to adverse pregnancy outcomes.⁷ Although pregnancy outcomes worsen as the ISS increases, the ISS remains nonpredictive for these outcomes because they may occur with low as well as with high scores.¹⁴ In fact, fetal demise may occur in the presence of an ISS as low as zero.⁹⁷ Although several studies have been performed in pregnant patients after minor trauma in an attempt to identify risk factors at admission (maternal obstetric variables, complaints, clinical findings, lab test results, fetal heart rate monitoring, or tocometer findings), which predict adverse pregnancy outcomes (e.g., placental abruption, preterm delivery, and neonatal low birth weight), there has been little success in identifying them.^15,98,99 Even in women who had sustained direct mild to moderate blunt trauma specifically to the abdomen, no association has been found between any of the potential predictors studied and poor obstetric outcomes.¹⁰⁰

C. Kleihauer-Betke testing. The Kleihauer-Betke (KB) blood test is a qualitative assessment of the amount of fetal hemoglobin in the maternal systemic circulation. A blood smear prepared from a sample of maternal blood is exposed to an acid, which removes adult hemoglobin from red blood cells. The smeared slide then undergoes hemoglobin-staining, which results in those red blood cells containing fetal hemoglobin appearing pink and those no longer containing adult hemoglobin appearing as “ghosts.” Stained cells are then counted microscopically in order to calculate the proportion of fetal to maternal cells. The test is generally used in Rh-negative mothers to determine the requirement for immune prophylaxis to inhibit maternal formation of Rh antibodies. Because the test is used to indicate the presence of transplacental fetomaternal transfusion, it was thought that the level of KB would indicate the presence of fetal hemorrhage and predict an adverse pregnancy outcome in cases of maternal trauma. Some studies suggest that KB testing may indeed predict the risk of preterm labor after maternal trauma.⁹⁹ Although elevated maternal serum α-fetoprotein exceeding 1,000 ng per mL is associated with adverse pregnancy outcomes after MVAs,¹⁰¹ others have found a similar incidence of positive KB tests in association with poor pregnancy outcomes in pregnant women who had undergone maternal trauma. However, in women with low-risk pregnancies, others have found no association between positive KB results in trauma and the presence of placental abruption or fetal distress¹⁰² or fetal or maternal morbidity.¹⁰⁰ The KB test may be inaccurate at least in part due to minor variations in laboratory methodology (e.g., the pH of the citric acid–sodium phosphate buffer being used or incubation time). The presence of a positive KB test alone thus does not necessarily indicate pathologic fetal–maternal hemorrhage in pregnant trauma patients,¹⁰² but it should prompt additional evaluation and testing.

D. Flow cytometry. Flow cytometry is an alternative diagnostic test that circumvents some of the problems associated with the KB screen.¹⁰³ In this test method, red blood cells are permeabilized to enable intracellular entrance of a specific antibody. Flow cytometric methods that use a monoclonal anti-hemoglobin F antibody for detecting fetal hemoglobin provide excellent discrimination between fetal and adult red blood cells. The test counts 50,000 cells, compared to the 2,000 counted in the KB test and may be sensitive to as little as 0.02% of hemoglobin F cells. However, this test requires validation in the maternal trauma setting.

      VII.Anesthetic considerations

Anesthetic management of the injured pregnant woman should be directed toward optimizing maternal oxygenation and perfusion.

A. Airway management. The incidence of difficult/failed intubation in obstetric anesthesia is four times higher than in the surgical nonobstetric population.¹⁰⁴ Difficult tracheal intubation may be encountered in up to 5% of pregnant women.^105,106 Precisely because of the urgency of the situation during induction of anesthesia in trauma cases, the anesthesiologist should always approach airway management with an alternative plan in mind. When preinduction preparation is possible, pulmonary damage caused by aspiration may be diminished through use of nonparticulate antacids that neutralize acidic pH prior to induction of anesthesia and drugs that increase the lower esophageal sphincter tone.¹⁰⁷ Although most trauma patients should be considered to have a full stomach and will likely undergo rapid sequence induction, this should not deter the anesthesiologist from prescribing oral antacids in cases where the patient is cooperative and there is no surgical contraindication (e.g., obtundation due to severe traumatic brain injury, upper gastrointestinal perforation). Tracheal intubation should be performed using a tube with an internal diameter of 0.5 to 1 mm smaller than that used for nonpregnant woman of similar size (i.e., 6.5 to 7.0 mm).

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