Imaging of Trauma: Part 2, Abdominal Trauma and Pregnancyâ€”A

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OBJECTIVE. The pregnant trauma patient requires imaging tests to diagnose maternal injuries and diagnostic tests to evaluate the viability of her pregnancy. This article will dis-cuss abdominal trauma in pregnancy and the specific role of diagnostic imaging. Radiation concerns in pregnancy will be addressed.

CONCLUSION. Trauma is the leading cause of nonobstetric maternal mortality and a significant cause of fetal loss. Both major and minor trauma result in an increased risk of fetal loss. In major trauma, when there is concern for maternal injury, CT is the mainstay of imag-ing. The risks of radiation to the pregnancy are small compared with the risk of missed or de-layed diagnosis of trauma. In minor trauma, when there is no concern for maternal injury but there is concern about the pregnancy, ultrasound is performed but is insensitive in diagnosing placental abruption. External fetal monitoring is used to dictate patient care.

Sadro et al.Abdominal Trauma and Pregnancy

Integrative ImagingReview

for fetal survival is maternal survival, and all efforts are made to save the mother. When the mother survives, the most common cause of pregnancy loss is placental abruption [5, 7, 15].

The purposes of this article are to briefly describe the clinical approach to managing the pregnant trauma patient, discuss the risks and benefits of imaging the pregnant trauma patient with modalities using ionizing radia-tion, show the normal CT appearance of the gravid uterus and the physiologic changes that occur during pregnancy, show traumatic conditions that occur in pregnancy and those traumatic conditions that place the fetus at most risk, and discuss strategies for preven-tion of trauma in pregnancy.

Clinical ManagementThe clinical management of the pregnant

trauma patient starts with maternal stabilization beginning with the ABCs of airway, breathing, and circulation. Caring for the pregnant trau-ma patient is challenging because of the altered physiology of pregnancy and because there are two lives at risk. A multidisciplinary approach that includes emergency medicine, trauma sur-gery, obstetrics and gynecology, radiology, and nursing is crucial in these patients.

After 20 weeks of gestation, the pregnant patient should be placed in the left lateral de-cubitus position to prevent compression of the inferior vena cava (IVC) by the gravid uterus

Imaging of Trauma: Part 2, Abdominal Trauma and Pregnancy—A Radiologist’s Guide to Doing What Is Best for the Mother and Baby

Claudia Sadro1

Mark P. Bernstein2 Kalpana M. Kanal3

Sadro C, Bernstein MP, Kanal KM

1Department of Radiology, Harborview Medical Center, 325 Ninth Ave, Seattle, WA 98104-2499. Address correspondence to C. Sadro ([email protected]).

2Department of Radiology, NYU Langone Medical Center, Bellevue Hospital, New York, NY.

3Department of Radiology, University of Washington Medical Center, Seattle, WA.

Integrat ive Imaging • Review

CME/SAM This article is available for CME/SAM credit.

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© American Roentgen Ray Society

Trauma is the leading cause of non-obstetric maternal mortality affect-ing up to 7% of pregnancies [1–13] and is a significant cause of

fetal loss [2–4]. Approximately 2% of level-1 trauma patients have a positive pregnancy test [12]. Pregnant trauma patients are more likely to sustain serious abdominal injury than non-pregnant trauma patients [5], and most obstet-ric complications of trauma occur in the third trimester [13]. Causes of trauma in pregnancy include motor vehicle crashes (49%), falls (25%), assaults and domestic violence (18%), and gunshot injuries (4%) [14] (Table 1). The incidence of domestic violence sharply in-creases in pregnancy [5, 6, 11–13, 15].

Both major and minor trauma result in an increased risk of pregnancy loss [5–12]. Patients with a higher injury severity score (ISS) are at greater risk of pregnancy loss. With an ISS > 25 [16], there is a 50% risk of fetal death [7]. However, fetal death may be seen with an ISS as low as 1 or 2 [10, 11]. Overall, the fetal loss rate in trauma is re-ported to be from 1% to 34% [5–12]. With penetrating abdominal injury, the fetal loss rate reaches 73% [17, 18].

Maternal death almost always results in fe-tal death [12]. Although there are reports of late third trimester pregnancies delivered by emer-gency cesarean section despite lethal maternal injuries, such cases are rare. The best chance

Keywords: fetal death, placental abruption, pregnancy, trauma, uterine rupture

DOI:10.2214/AJR.12.9091

Received April 13, 2012; accepted after revision June 13, 2012.

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[19–21]. Evaluation of the fetus only begins after maternal stabilization [20]. A fetus can survive delivery after 24–26 weeks of gesta-tion or 500 g [20]. Continuous external fetal monitoring with devices that measure fetal heart rate and uterine tone and contractili-ty is performed in pregnant trauma patients beyond 24 weeks of gestation for at least 4 hours and is the most sensitive test to diag-nose placental abruption, preterm labor, and fetal distress [20]. Signs of placental abrup-tion and fetal distress on external fetal mon-itoring include increased uterine tone and contractility and worrisome fetal heart tones, including fetal bradycardia and late decelera-tions (Fig. 1). Such signs beyond 24 weeks prompt emergency cesarean delivery [3].

ImagingIn major trauma, the pregnant trauma pa-

tient is imaged with radiography, CT, and an-giography as necessary. Imaging begins with portable radiography of the chest and, when clinically indicated, the pelvis. Focused ab-dominal sonography for trauma (FAST) is performed in the trauma bay to identify free intraperitoneal fluid and pericardial fluid. Ul-trasound also enables determination of gesta-tional age, fetal heart rate, amniotic fluid vol-ume, and placental position. Unfortunately, although free of ionizing radiation, ultrasound is of limited utility in detecting maternal inju-ries, including active arterial bleeding.

Radiography, CT, and angiography pro-duce ionizing radiation. In major trauma, the risks of radiation to the pregnancy are small compared with the risk of missed or delayed diagnosis of maternal injury.

CT is the proven modality for the evaluation of trauma patients and remains the test of choice for injured pregnant patients. However, efforts are made to eliminate unnecessary scans, re-duce overlap of body sections, and avoid mul-tiple passes where possible. It is important to

generate a diagnostic test, and for that reason extreme low-dose protocols are not used.

At Harborview Medical Center, diagnos-tic abdominopelvic CT is performed in the portal venous phase after a 70-second de-lay. The typical contrast regimen for patients weighing between 122–200 lbs (55.3–90.7 kg) is 150 mL delivered at 3.5 mL/s. For a 16-MDCT scanner, we use a section thickness of 2.5 mm; pitch, 1.375; noise index, 16.1; and 120 kV. The tube current–time product depends on patient size and is approximately 240 mAs (effective mAs, 175). The radiolo-gist checks the scan while the patient is on the CT table. Delayed scans at 5–10 minutes are performed selectively to evaluate for col-lecting system rupture in the setting of renal trauma or to evaluate for active bleeding into hematomas when the diagnosis is in doubt on the initial scan. Delayed scans are focused on the area of interest and are performed with a lower dose than the initial scan, in which the noise index is increased to 22.1 and, in the case of renal trauma, the kilovoltage is de-creased to 100. CT cystography is performed in at-risk patients to evaluate for bladder rup-ture if there is gross hematuria and stranding or fluid around the bladder or if there is mi-croscopic hematuria in the setting of a pelvic fracture or penetrating trauma. CT cystogra-phy is performed with a very-low-dose tech-nique with the noise index increased to 32.6. CT scans of the spine and bony pelvis are re-constructed from the original dataset. This is the same protocol used in nonpregnant trau-ma patients at Harborview Medical Center.

The decision to perform abdominopelvic CT in a pregnant trauma patient to diagnose serious abdominal injury typically encountered in high-energy trauma, such as motor vehicle crashes, is at the discretion of the treating physician. Se-rious abdominal injury is more common in pregnant trauma patients than in nonpregnant trauma patients [5]. In a retrospective study of

two level 1 trauma centers performed by Low-dermilk et al. [12], 7.9% of pregnant trauma patients were evaluated with CT and 50% of those patients presented in the third trimester.

IV iodinated CT contrast material is a Food and Drug Administration (FDA) cate-gory B agent with no known adverse effects to the pregnancy and is administered as nec-essary [22, 23]. Specifically, it does not al-ter neonatal thyroid function [24, 25]. MRI is safe in pregnancy at 1.5 T, although it is rarely performed in acute trauma because it removes the patient from emergency person-nel, is a difficult setting to monitor the pa-tient, and is time intensive. Unlike CT con-trast material, however, gadolinium is an FDA category C agent with known terato-genic effects in animals and is contraindicat-ed in pregnancy [22, 23].

Angiography is performed to diagnose and treat active bleeding in critically injured pregnant trauma patients who do not meet the criteria for emergency surgery. Efforts are made to reduce the dose from fluoroscopy delivered to the gravid uterus. If the patient is stable enough to first undergo CT, the in-terventional radiologist reviews the CT scan to determine the most likely site of bleeding to minimize the number of vessels that need to be injected. The interventional radiologist can use strategies to keep the fetal dose to a minimum, such as minimizing fluoroscopic time, decreasing the fluoroscopy frame rate, minimizing the number of spot films by us-ing the last image hold feature when appli-cable, tailoring the digital subtraction angi-ography (DSA) frame rate and total number of frames in a sequence to the anatomic area and blood flow rate being imaged, and using image magnification only as necessary. The patient is imaged semisupine and postero-anterior with the x-ray tube situated poste-rior and the image intensifier anterior and as close to the patient as possible with optimal collimation. If the site of bleeding is not the pelvis, a lead shield may be placed posterior to the gravid uterus. Arm or neck access may be considered in these patients [26, 27].

Informed consent is recommended when radiography, CT, or fluoroscopic procedures are performed through the gravid uterus and when IV iodinated contrast material is admin-istered to pregnant patients [23, 28]. Howev-er, in seriously injured patients, the medical emergency does not permit the full consent process. In these cases, standard institutional procedure should be followed to document the necessity of the procedure [12, 26, 27].

TABLE 1: Cause of Trauma in Pregnant Patients [14]

Trauma Type Cause Percentage

Blunt trauma

Motor vehicle crashes 49

Falls 25

Assaults 18

Burns 1

Penetrating trauma

Gunshot wounds 4

Stab wounds


Abdominal Trauma and Pregnancy

The risk of childhood cancer from in utero exposure to ionizing radiation exists through-out pregnancy. Several reports place the back-ground risk of childhood cancer mortality at 0.14%. An in utero exposure of 10 mGy increas-es this risk by 0.06% [31, 40, 41], which trans-lates to 1 excess cancer death per 1700 [32]. According to the American College of Radiolo-gy Practice Guideline for Imaging Pregnant or Potentially Pregnant Adolescents and Women with Ionizing Radiation, exposure of the new-born child to 10 mGy of ionizing radiation in-creases the absolute lifetime risk of develop-ing cancer by 0.4% and exposure to 50 mGy increases this risk by 2% [28]. It is assumed that this also reflects the potential risk to the conceptus in utero for the second and third tri-mesters and part of the first trimester, although there are uncertainties with this estimate.

It is important to estimate the fetal radiation dose in pregnant patients who undergo radi-ography, CT, or fluoroscopy, and the medical physicist is actively involved in this process [32]. At Harborview Medical Center, a ther-moluminescent dosimeter is placed on the ab-domen of all pregnant patients imaged with radiography, CT, and fluoroscopy. The skin

Although the initial assessment of the preg-nant trauma patient is performed with CT, fol-low-up imaging of abdominal or pelvic trau-ma may be performed with ultrasound or unenhanced MRI to reduce the cumulative dose from multiple CT examinations. For ex-ample, certain hematomas may be followed with ultrasound, and pancreatic duct injuries may be evaluated with MRCP [29, 30].

Radiation Risks and PregnancyIonizing radiation has potentially harmful

effects on living tissue. The fetus is more sen-sitive to the harmful effects of ionizing radia-tion than children and adults. Fetal risks from ionizing radiation include small head size, mental retardation, organ malformations, can-cer, and death [31]. This has led to reluctance among physicians to perform radiography and CT in pregnancy.

Background radiation experienced by the fe-tus over the 9 months of gestation is approxi-mately 1 mGy [32]. Fetal radiation exposures of less than 1 mGy are not significant and do not require counseling [32]. Table 2 lists fetal doses for common radiographic examinations and Table 3 lists fetal doses for common CT ex-aminations. When the fetus is not in the FOV, the radiation dose is negligible. When the fe-tus is directly irradiated for pelvic radiography, the dose is approximately 1–3 mGy [33]. The fetal dose from a typical CT of the abdomen and pelvis is 25 mGy [33]. A recent study that used Monte Carlo simulations of pregnant pa-tient models representing a range of gestation-al ages and maternal sizes found that the fetal dose from CT did not depend on the gestational age of the pregnancy but rather on the maternal abdominal perimeter and the depth of the fetus from the anterior maternal skin surface. A larg-er maternal perimeter and a greater depth of the fetus from the anterior maternal skin surface re-sulted in a smaller fetal dose. The average fetal dose in that study was 24 mGy for a 16-MDCT scanner using typical scanning parameters and ranged from 16 to 31 mGy depending on mater-nal size [34]. The fetal dose will vary depend-ing on scanning parameters. With modern CT scanners that use automated exposure control, the fetal dose may be reduced further and was reported to be as low as 13 mGy for CT of the abdomen and pelvis by Wieseler et al. [35]. The fetal dose from fluoroscopy over the gravid uterus for pelvic angiography is 20–100 mGy/min depending on maternal thick-ness and the number of vessels injected [36].

In 1977, the National Council of Radiation Protection and Measurements issued the fol-

lowing policy statement with regard to radia-tion and pregnancy [37]: “The risk [of abnor-mality] is considered to be negligible at 50 mGy or less….” A similar conclusion was drawn by the American College of Obstetricians and Gy-necologists in 2004 in the following statement [38]: “Women should be counseled that x-ray exposure from a single diagnostic procedure does not result in harmful fetal effects. Specif-ically, exposure to less than 5 rad [50 mGy] has not been associated with an increase in fetal anomalies or pregnancy loss.”

The risks of ionizing radiation to the fetus depend on the dose and the gestational age at exposure (Table 4). In the first 2 weeks af-ter conception, the main risk is spontaneous abortion. The effect is all or none and is only observed at doses greater than 50–100 mGy [39]. Teratogenic effects, such as small head size, mental retardation, and organ malforma-tions, are only observed at high doses (typi-cally greater than 100 mGy) between 2 and 15 weeks after conception. This is the peri-od of organogenesis and rapid neuronal devel-opment and migration [39]. (Gestational age is used clinically and equals the weeks after conception plus 2 weeks.)

TABLE 2: Fetal Absorbed Dose from Selected Radiographic Examinations

Examination Fetal Absorbed Dose (mGy)

Cervical spine (anteroposterior, lateral) < 0.001

Extremities < 0.001

Chest (posteroanterior, lateral) 0.002

Thoracic spine (anteroposterior, lateral) 0.003

Abdomen (anteroposterior) 1–3

Lumbar spine (anteroposterior, lateral) 1

Background fetal dose for 9 months of pregnancy 0.5–1

Note—Doses to conceptus and background dose to the conceptus obtained from [33]. A radiation shield is applied over the gravid abdomen when not in the imaging field.

TABLE 3: Fetal Absorbed Dose from Selected CT Examinations

Examination

Fetal Absorbed Dose (mGy)

Referencea Referenceb

CT head 0

CT chest 0.2 0.02

Pulmonary CT angiography 0.2 0.02

CT abdomen 4 1.3

CT abdomen and pelvis 25 13

CT kidneys, ureters, and bladder 10 11

Background radiation for 9 months of pregnancy 0.5–1

Note—A radiation shield is typically applied over the gravid abdomen when not in the imaging field although the effect is minimal.

aCT doses to conceptus and background dose to the conceptus obtained from [33].bCT doses to conceptus obtained from [35].


Sadro et al.

dose is recorded and is reviewed by the medi-cal physicist. We can estimate the fetal dose to be equal to approximately one third of the skin entrance dose for radiographic and fluoroscop-ic procedures using anteroposterior technique (less for posteroanterior or lateral views) for the average patient [42]. When the estimated fetal dose is 50 mGy or greater, a detailed dose calculation is performed by the medical phys-icist. Any pregnant patient who undergoes a high-dose examination, such as CT or fluo-roscopy, through the gravid uterus will have a detailed fetal dose calculation. The total skin entrance dose and fetal dose calculations are recorded in the patient’s medical record with an explanation of the expected risks to her pregnancy. This is explained to the patient by the attending physician in charge of her care while in hospital. It would very unusual for the fetal dose to approach the actionable level of 150 mGy (when therapeutic abortion might be considered) in diagnostic imaging even in the major trauma setting.

CT in PregnancyNormal Appearance of the Gravid Uterus

It is important to recognize the normal ap-pearance of the gravid uterus when reading CT scans in pregnant women. In the first trimester, the gestational sac is seen as a low-attenuation endometrial cystic structure. There may be pro-nounced endometrial enhancement. The pla-centation site is identified late in the first trimes-ter [12, 43] (Fig. 2A). In the second trimester, early ossification of fetal parts is seen. The pla-centa heterogeneously enhances and is clear-ly delineated from underlying myometrium. Deep in relation to the placenta are enhanc-

ing engorged veins representing the retropla-cental venous plexus [12, 43] (Fig. 2B). Begin-ning late in the second trimester, the placental cotyledons become well formed and are charac-terized by central areas of low attenuation with intervening rings of higher attenuation [12, 43]. The fetal skeleton is ossified with clearly de-lineated organs. Very little IV contrast materi-al crosses the placenta into the fetal circulation, and there is no detectable enhancement of fe-tal tissue [12] (Fig. 2C). Throughout gestation, the normal amniotic fluid is low density [12].

Physiologic Changes of PregnancyOver the course of pregnancy, the cardi-

ac output increases from 4.5 to 6.0 L/min, with uterine blood flow increasing from 1% to 10% of the cardiac output [44]. Physiolog-ic changes of pregnancy may be observed on CT in the second and third trimesters. The pelvic and ovarian veins enlarge, the latter approaching the size of the IVC [3] (Figs. 2B and 2C). The spleen enlarges as much as 50% during pregnancy [45]. Maternal hydro-nephrosis (greater on the right) is common in pregnancy with the kidneys enlarging by up to 1.5 cm [46] (Fig. 2D). Laxity of the pel-vic ligaments results in mild widening of the symphysis pubis and sacroiliac joints. One may observe a rim-enhancing corpus luteum cyst in the ovary in the first trimester [12].

Traumatic Injuries in PregnancyMaternal Injury

The pregnant patient is predisposed to the same spectrum of injuries encountered in non-pregnant trauma patients. However, retroperito-neal hemorrhage is more common in pregnant

trauma patients because of increased pelvic blood flow [3] (Fig. 3). The gravid uterus dis-places the liver and spleen against the ribs and elevates the bladder out of the pelvis, making these more prone to injury [3, 20]. Moreover, as the kidneys and spleen enlarge, they are further susceptible to injury [3] (Fig. 4).

Certain injuries in pregnancy are associat-ed with an increased risk of fetal loss. Pelvic and acetabular fractures occurring in preg-nancy are associated with a high maternal (9%) and higher fetal (35%) mortality, in-creasing to 75% for severe fracture patterns [47] (Fig. 5). In penetrating abdominal trau-ma, uterine and fetal injury increase as the gravid uterus enlarges, while offering great-er maternal protection [18].

When the mother survives, the most com-mon causes of fetal death are placental abrup-tion and maternal hemorrhage. A pregnant woman can lose 30% of her blood volume be-fore her vital signs change [20]. Because there is no uterine autoregulation, maternal blood pressure does not accurately reflect uterine blood flow. Maternal hemorrhage causes pro-nounced uterine artery vasoconstriction that protects maternal hemodynamics while lead-ing to fetal hypoxia, acidosis, and even death [3, 4, 20]. Severe maternal head injury is as-sociated with an increased risk of fetal loss thought to be due to alteration in the hypotha-lamic-pituitary-adrenal axis [4, 9] (Fig. 4).

Maternal death almost always results in fetal death. Head injury and hemorrhagic shock ac-count for the majority of maternal deaths. The maternal death rate from serious injuries is no different from the death rate in nonpregnant trauma victims [3].

TABLE 4: In Utero Effects of Diagnostic Levels of Ionizing Radiation [70]

Weeks After Conception Stage of Development Biologic Effects to Conceptus

0–2 weeks Preimplantation Prenatal death (all or none)

Risk at > 50–100 mGy

2–8 weeks Major organogenesis Organ malformations

Risk threshold > 100 mGy (but not observed in humans at diagnostic levels)

2–15 weeks Organogenesis and rapid neuronal development and migration Small head size

Risk threshold > 100 mGy

Severe mental retardation

Risk threshold > 100 mGy

2 weeks to term Postimplantation Childhood cancer (< 15 years old)

Risk childhood cancer death 0.06% per 10 mGy (or 1/1700)a

Lifetime cancer risk 0.4% per 10 mGyb

aData from [31].bData from [28].



Injury to the Gravid UterusComplications of trauma to the gravid

uterus include spontaneous abortion, preterm labor, premature rupture of membranes, pla-cental abruption, placental laceration and in-farction, and uterine laceration and rupture. Most injuries to the gravid uterus occur in the third trimester.

The most common injury to the gravid uterus after blunt trauma is placental abrup-tion. Abruption is the result of shearing be-tween the relatively elastic uterus and rigid placenta. The incidence of placental abrup-tion is 1–5% with minor trauma and 30–50% with major trauma [2, 3, 5]. Risk factors in-dependent of trauma include advanced ma-ternal age, tobacco use, cocaine use, ma-ternal hypertension, and preeclampsia [48]. Clinically, placental abruption presents with uterine pain and irritability with or without vaginal bleeding. Marginal placental ab-ruption occurs when there is uteroplacental separation at the placental margin. Retro-placental abruption involves the central pla-centa and carries a worse prognosis. Placen-tal abruption can lead to preterm labor, fetal distress, low birth weight, oligohydramni-os, fetal death, and maternal coagulopathy secondary to release of thromboplastic sub-stances from the placenta [3]. Small placen-tal abruptions may be well tolerated. The larger the abruption, the worse the progno-sis, with greater than 50% abruption leading to 75% fetal mortality [48–50].

In minor trauma when there is no concern for maternal injury but there is concern about the pregnancy, radiologists often perform ul-trasound to diagnose placental abruption. Unfortunately, ultrasound is insensitive for abruption and is false-negative in 50–80% of cases [20, 48, 51]. Therefore, a negative ultrasound cannot exclude placental abrup-tion. When positive, ultrasound shows ret-roplacental hemorrhage that is hyperechoic acutely, becoming hypoechoic over time. It may be isoechoic to the placenta at the time of scanning, in which case one only observes apparent focal thickening of the placenta [52] (Fig. 6). The normal placenta measures 1 mm thick for each week of gestation. At 30 weeks, the normal placenta is 30 mm thick [48, 53]. Normal retroplacental venous plex-us can be differentiated from retroplacen-tal hemorrhage by applying color Doppler ultrasound. With placental abruption, one may also see echogenic amniotic fluid due to bleeding into the amniotic cavity [53].

The diagnosis of placental abruption may be made on CT when the pregnant trauma pa-

tient is scanned to exclude maternal injury. A lacerated or partially devascularized placen-ta may be seen as focal diminished enhance-ment extending from the placental base to the placental surface [12, 43] (Figs. 7 and 8). Over time, this may lead to placental infarc-tion. One may see apparent focal placental thickening from retroplacental clot that may be difficult to distinguish from normal pla-centa or a myometrial contraction [43]. With placental abruption, one may occasionally see hyperdense amniotic fluid from bleeding into the amniotic cavity [12]. The accuracy of CT in the diagnosis of placental abruption in the pregnant trauma patient is controver-sial. Most studies to date lack scientific rigor due to small patient numbers and the lack of a reference standard [43, 54]. Certainly, CT is not recommended for diagnosing placental abruption in pregnancy because of the risks of ionizing radiation in pregnancy. However, when CT is performed to diagnose maternal injuries, it is important for the radiologist to recognize placental abruption when evaluat-ing the gravid uterus.

CT may be false-negative in predicting pla-cental abruption (Fig. 9). Conversely, chronic placental infarcts in late third trimester preg-nancies may cause a false-positive diagno-sis for placental abruption [43] (Fig. 10). The CT appearance of late third trimester placen-tas may also be confusing due to prominent chorionic villous plate indentations that may resemble ischemic changes and venous lakes that may resemble active bleeding into the pla-centa (Figs. 5 and 11). The imaging findings are always correlated with the external fetal monitoring, which remains the most sensitive test to diagnose placental abruption. Findings of placental abruption and fetal distress on ex-ternal fetal monitoring prompt emergency ce-sarean section [3] (Fig. 1). Delayed scanning would significantly contribute to fetal dose and is not performed to evaluate the placenta.

Uterine laceration and rupture are uncom-mon, seen in less than 1% of pregnant ma-jor trauma patients [21]. Uterine rupture is one of the most life-threatening emergencies in obstetrics [14], associated with near 100% fetal mortality. Maternal mortality occurs in fewer than 10% of cases and usually results from associated injuries [3, 55]. Prior cesar-ean section, previous uterine surgery, and congenital uterine anomalies [14] increase the risk for uterine rupture in blunt trauma. Penetrating trauma is an independent risk factor [21, 56]. Patients present with pain, shock, and absent fetal heart tones. The diag-nosis of a uterine laceration is difficult with

ultrasound [56, 57]. On CT, a uterine lacera-tion presents as diminished enhancement of the myometrium, which may appear thinned with deep or full-thickness lacerations [12, 56]. The most extreme cases present with an empty uterus and free-floating fetus sur-rounded by amniotic fluid, blood, and some-times placenta [12, 56] (Fig. 12).

Injury to the FetusDirect fetal injury is uncommon in the

pregnant trauma patient because the fetus is afforded protection by the maternal body wall, uterus, and amniotic fluid [3, 21]. By the late third trimester, the volume of amni-otic fluid relative to the volume of the fetus is decreased, providing less cushion effect. The most common injuries to the fetus are skull fracture and head injury, seen in the late third trimester with cephalic presenta-tion, often in the setting of a maternal pel-vic fracture [58] (Fig. 8). Fetal head injury is almost universally lethal to the fetus [59].

Penetrating TraumaPenetrating trauma in pregnancy is less com-

mon than blunt trauma, accounting for 9% of abdominal trauma in pregnancy in one series [18]. Most result from gunshot wounds [18]. The gravid uterus offers protection to the moth-er; however, direct uterine and fetal injuries are increased [14, 17, 18, 56]. The fetal death rate is 71–73% for uterine gunshot wounds and 27–42% for stabbings [17, 21, 60].

PreventionTrauma is the leading cause of nonobstet-

ric maternal mortality, and much attention has been drawn to prevention. Most serious injuries occur as a result of motor vehicle crashes. Fetal mortality is 1–2% from minor crashes, rising to 30–50% in major crashes [61]. Properly placed shoulder-lap belts have protective effects on the mother and her fetus in all trimesters of pregnancy, and their use is recommended by the National Highway Traffic Safety Administration (NHTSA) and the American College of Obstetrics and Gy-necology. However, many pregnant women do not use seat belts or do not use them cor-rectly [4, 62]. The lap portion should be placed as low as possible on the hips, never above the abdomen because this may cause injury to the gravid uterus [21, 63]. The use of airbags in pregnancy is controversial. Air-bags deploy at high velocity and at high force, and the force is greater the closer one is to the airbag deployment device [64]. In the third tri-mester of pregnancy, the gravid uterus may be


Sadro et al.

positioned very close to the airbag deploy-ment device and is susceptible to strong forces if the airbag deploys. Airbag deployment has been implicated in direct fetal injury and pla-cental abruption in late third trimester preg-nancies in several case reports [65–67]. De-powered and multistage airbags are being installed in newer vehicles for safety reasons [64]. The NHTSA is currently evaluating its position on the use of airbags in pregnancy [63]. As a rule, drivers and passengers should sit at least 10 inches (25 cm) from the airbag deployment device. If this is not possible, the airbag should be disconnected [62].

Domestic violence is such an important cause of trauma in pregnancy that pregnancy itself is an independent risk factor for trauma in young women. The trauma from domestic violence is often directed at the gravid abdo-men [14] and may threaten the mother and her pregnancy [11, 68]. Up to 10% of abused women are pregnant, with a miscarriage rate of 5% [68]. Emergency personnel should rou-tinely inquire about domestic violence when pregnant women present for medical care.

Substance abuse is a common problem in trauma victims, including pregnant women. The incidence of substance abuse in pregnant trauma patients in the form of drugs or alcohol is 13–20% [4]. Prenatal care visits should in-clude prevention programs aimed at reducing substance abuse, especially in young women.

ConclusionTrauma is the leading cause of nonobstet-

ric maternal mortality and a significant cause of fetal loss. Managing the pregnant trauma patient requires a multidisciplinary approach. In high-energy trauma when there is concern for maternal injuries, CT is the mainstay of imaging. The risks of radiation to the preg-nancy are small compared with the risk of missed or delayed diagnosis of trauma. With rare exception, there is no fetal survival with-out maternal survival and imaging should be performed without delay. Radiologists must be familiar with the normal and abnormal appearance of the gravid uterus in pregnant trauma patients undergoing CT. In low-en-ergy trauma when there is no concern about maternal injuries but there is concern about the fetus, ultrasound is performed to evaluate the pregnancy. Radiologists must be aware that ultrasound is insensitive in diagnosing placental abruption and a negative ultrasound examination does not exclude this diagnosis. External fetal monitoring is used to dictate patient care. Trauma prevention is important

in pregnancy. Pregnant patients are advised to wear seat belts correctly when in a motor vehicle. The use of airbags is controversial.

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Sadro et al.

Fig. 1—Readout from external fetal cardiotocography monitoring in woman with placental abruption requiring emergency cesarean section. Uterine contractions are occurring every minute with increasing baseline tone as tracing evolves (lower strip). Fetal heart rate shows variable-appearing deceleration evolving into prolonged fetal deceleration (upper strip). Toward end of tracing, fetal heart signal is lost and when regained, fetal heart rate is in 70–80 beats/min (bradycardic) range, warranting emergency cesarean section. (Reprinted with permission from [69])

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Fig. 2—Normal CT of gravid uterus.A, 35-year-old woman who is 8 weeks pregnant. Normal first trimester CT image of gravid uterus shows intrauterine gestational sac as low-attenuation cystic structure. There is pronounced endometrial enhancement (arrow). Placentation site is not visualized.B, 33-year-old woman who is 15 weeks pregnant. Normal CT image of gravid uterus shows early ossification of fetal parts. Placenta (P) is forming on right side of uterus with heterogeneous enhancement. There are enhancing engorged veins deep in relation to placenta representing retroplacental venous plexus (arrowheads). There is marked enlargement of pelvic veins bilaterally (arrows).C, 26-year-old woman who is 26 weeks pregnant. Normal late second trimester CT image of gravid uterus shows anterior placenta with well-defined cotyledons characterized by central areas of low attenuation with intervening rings of higher attenuation (asterisks). Fetal parts are ossified and amniotic fluid is low density. Very little iodinated contrast material crosses placenta, so there is no enhancement of fetal liver (L). Right ovarian vein is enlarged to one half size of inferior vena cava (arrow).D, 24-year-old woman who is 35 weeks pregnant. Normal third trimester CT image of gravid uterus and kidneys shows bilateral hydronephrosis, greater on right (arrows). Placenta is posterior with heterogeneously enhancing cotyledons (asterisk).

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Fig. 4—18-year-old woman who is 14 weeks pregnant and was restrained passenger in T-bone high-speed motor vehicle crash.A, CT image of head shows shear hemorrhage in splenium of corpus callosum (arrow) and small amount of intraventricular blood (not shown).B, Contrast-enhanced CT image through abdomen shows grade 2 splenic laceration (arrowhead) and small hemoperitoneum (arrow).C, CT image through gravid uterus is normal with anterior placenta (arrow) and early ossification of fetal parts (arrowhead). There is small hematoma in left pelvic sidewall (asterisk) due to pelvic fracture. Patient had lateral compression injury of bony pelvis with zone 1 fracture of left sacral ala and left obturator ring fracture (not shown). CT cystography performed for hematuria was negative for bladder injury (not shown).D, Limited obstetric ultrasound image obtained next day shows fetal death with intrauterine gestation with no fetal cardiac activity. Placenta was normal on ultrasound. Patient was treated with dilatation and curettage and had internal fixation of pelvic fracture.

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Fig. 3—25-year-old intoxicated woman who is 21 weeks pregnant and was restrained passenger in head-on high-speed motor vehicle crash.A, Contrast-enhanced CT image of abdomen and pelvis shows right retroperitoneal hemorrhage (asterisk) centered on enlarged right ovarian vein (arrowhead).B, CT image through gravid uterus shows normal anterior placenta. Arrowheads show nonenhancing chorionic villous plate indentations that should not be confused with abnormality. There are enhancing engorged veins in right adnexa (asterisk). Patient also sustained multiple pelvic and acetabular fractures (not shown). Mother and fetus did well.


Sadro et al.

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Fig. 5—39-year-old woman who is 38 weeks pregnant and is hemodynamically stable. She was restrained driver in high-speed motor vehicle crash.A and B, CT images through pelvis show diastasis of left sacroiliac joint (arrowhead, A) and bilateral obturator ring fractures (arrows, B) from anteroposterior compression injury.C, Contrast-enhanced CT image of abdomen and pelvis shows areas of nonenhancement in posterior placenta (asterisk) concerning for ischemia and areas of contrast blush (arrow) concerning for active bleeding. Venous lakes and chorionic villous plate indentations provide alternate explanation because external fetal monitoring at this time was normal (see also Fig. 11). Delayed scans are not performed to evaluate placenta because it would not change management and would significantly add to fetal dose.D, CT image through pelvis shows large hematoma deep in relation to left groin with active contrast extravasation (arrow).E, Emergency angiogram with selective injection of left external iliac artery shows active extravasation from left inferior epigastric artery (arrow) that was treated with embolization coils. Later, in ICU, there were increasing uterine contractions and worrisome fetal heart tones on external fetal monitoring concerning for placental abruption prompting emergency cesarean section. Mother and infant did well. Pelvic fracture was treated conservatively.

Fig. 6—19-year-old woman who is 24 weeks pregnant and sustained multiple blows to her abdomen in mosh pit 1 week before admission. Moshing is form of slam dancing. She had uterine contractions over past week and developed severe abdominal pain and vaginal bleeding on day of admission.A, Color Doppler ultrasound image of placenta (P) shows apparent thickening of placenta due to large retroplacental hematoma (H) that is heterogeneously hypoechoic to placenta without internal color flow.B, Follow-up ultrasound image of placenta obtained 3 weeks later after bed rest in hospital reveals contraction of clot (H) that has become hypoechoic to placenta (P). There was no rupture of membranes. Vaginal bleeding and uterine contractions stopped. Patient was discharged with close interval follow-up. (Reprinted with permission from [69])



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Fig. 7—23-year-old woman who is 20 weeks pregnant and was pedestrian hit by car on right side of her body.A and B, Contrast-enhanced CT images of abdomen and pelvis show grade 4 hepatic laceration (arrow) and small hemoperitoneum. There is normal bilateral hydronephrosis of pregnancy.C, CT image through gravid uterus shows posterior placenta with marginal placental abruption on left with intermediate-density clot elevating placenta from uterine wall (asterisk). Engorged right ovarian vein (arrow) and dilated ureters (arrowheads) are normal in pregnancy. She also sustained comminuted right femur fracture (not shown). Ultrasound revealed normal fetal heart tones and movement. Femur fracture was treated with open reduction and internal fixation, and patient had subsequent uneventful pregnancy.

Fig. 8—20-year-old woman who is 39 weeks pregnant and was restrained driver who swerved head on into traffic and was T-boned by bus on driver’s side at 60 miles/h (96.6 km/h) with airbag deployment. She was intubated at scene for loss of consciousness.A, Contrast-enhanced CT image of abdomen and pelvis shows placenta on right with near-complete devascularization indicative of severe abruption (asterisk). There are only small areas of enhancing placenta (arrowhead). Patient was in right posterior oblique position rather than left, and there is compression of inferior vena cava by gravid uterus (arrow).B, CT image obtained lower through gravid uterus shows cephalic presentation of fetus. There is displaced fracture of right fetal parietal bone (arrow) with intracranial blood (asterisks).C, Bone windows image shows zone 2 left sacral fracture (arrow) and fracture of left obturator ring (not shown). While in CT, patient showed evidence of preterm labor and worrisome fetal heart tones. Emergency cesarean section was performed immediately after CT for placental abruption. Surgery confirmed retroplacental clot and bloody amniotic fluid. Infant had Apgar scores of 1–1-1 and died after 34 minutes of resuscitation. Autopsy report revealed that cause of death was fetal head injury with skull fracture, brain laceration, and intracranial hemorrhage. Mother did well. (Reprinted with permission from [58])


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Fig. 9—33-year-old woman who is 33 weeks pregnant and sustained 20-foot fall from balcony after using alcohol and cocaine.A, Contrast-enhanced CT image of abdomen and pelvis shows anterior placenta (asterisk) that appears normal.B and C, CT images of pelvis show diastasis of sacroiliac joints (arrows, B) and symphysis pubis (arrow, C) from anteroposterior compression injury. There is also hematoma in space of Retzius without active contrast extravasation (not shown). Patient also had open comminuted intraarticular distal left femur fracture (not shown). External fetal monitoring showed moderate fetal heart rate variability and minimal contractions early on. Later on day of admission, there were fetal decelerations and increased uterine contractions in keeping with placental abruption. Patient had emergency cesarean section and delivered live infant. She was treated for her injuries.

Fig. 11—39-year-old woman who is 39 weeks pregnant and was restrained front seat passenger in rear-end motor vehicle crash. She has history of juvenile rheumatoid arthritis and was scheduled for elective cesarean section in 2 days.A and B, Contrast-enhanced CT images of abdomen and pelvis show multiple areas of nonenhancement of placenta, most pronounced on amniotic surface (asterisk). There are also areas of contrast medium pooling (arrow, A) that were concerning for active bleeding into placenta at time. Incidental note is made of enhancing fibroid in posterior left uterine body (F) in A, necrotic fibroid deep in relation to placenta in right uterine body (F) in B, and engorged veins in right pelvic sidewall (arrow, B). External fetal monitoring showed contractions every 5–8 minutes but normal fetal heart tones. There was no vaginal bleeding. Ultrasound of pregnancy and placenta showed normal findings. Patient underwent regularly scheduled cesarean section 2 days later with no complications. Obstetrician did not report anything unusual about placenta. Patient sustained no other injuries. It is thought that unusual appearance of placenta was due to prominent chorionic villous plate indentations and venous lakes rather than sequela of trauma. Delayed imaging is not performed to evaluate placenta because it would not change management and would significantly add to fetal dose.

Fig. 10—22-year-old woman who is 31 weeks pregnant and was involved in motor vehicle crash. Contrast-enhanced CT image of abdomen and pelvis shows several areas of nonenhancing placenta (asterisk). Obstetric ultrasound and ultrasound of placenta were normal. Patient sustained no other injuries. External fetal monitoring over 4 hours was normal. Patient was assumed to have had chronic placental infarcts unrelated to acute trauma and was discharged.



Fig. 12—Woman who is 36 weeks pregnant and was restrained passenger in motor vehicle crash. Fetal heart tones and motion were absent at screening ultrasound.A and B, Contrast-enhanced CT images of abdomen and pelvis show uterine rupture with free floating fetus (F, A) and empty uterus (U, B). There is free intraperitoneal fluid that may represent blood and amniotic fluid. Complete posterior fundal rupture was found at surgery and extruded fetus was dead. Patient recovered from her other injuries. (Reprinted with permission from [12])

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F O R Y O U R I N F O R M A T I O N

The reader’s attention is directed to part 1 accompanying this article, titled “Imaging of Trauma: Part 1, Pseudotrauma of the Spine—Osseous Variants That May Simulate Injury,” which begins on page 1200.

F O R Y O U R I N F O R M A T I O N

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