Prehospital care is an extension of the trauma system (see Chapter 4) and must be appropriately adapted to the needs of the injured gravid patient. In particular, the importance of providing an adequate airway and supplemental oxygen to prevent fetal hypoxia must take priority during field transport. Also, it is important to recognize that the relative hypervolemia of pregnancy may mask the usual signs and symptoms of acute blood loss. Thus, intravenous fluids should be given liberally during transport in these patients. A wedge placed under the right hip may help avoid the vena cava compressive syndrome described above. Any information on the length of the gestation and prenatal care and complications that can be obtained should be relayed to the receiving trauma center.
As with any other injured patient, the primary survey of the injured pregnant patient addresses the airway, breathing, and circulation, with the mother receiving treatment priority (see Chapter 10). Ensuring an adequate maternal airway with supplemental oxygen is essential for preventing maternal and fetal hypoxia (see Chapter 11). Because the oxyhemoglobin dissociation curve for fetal blood is different from that for maternal blood, small increments in maternal oxygen concentration improve the blood oxygen content and reserve for the fetus, even though the maternal arterial oxygen content does not change appreciably. Of note, because pseudocholinesterase levels decrease during pregnancy, lower doses of succinylcholine may be used during rapid sequence intubation.24 As mentioned above, due to the expansion of the intravascular volume, signs of shock in the mother may be delayed until over 35% of blood loss has occurred; however, the fetus will be in jeopardy before this point. Thus, fluid and blood resuscitation should be vigorous. In late pregnancy, it is wise to refrain from the use of femoral catheters for resuscitation. Although the role of ED thoracotomy in pregnancy remains to be defined, it is the opinion of the authors that it should be considered in conjunction with perimortem cesarean section (see below).25
Secondary Survey and Maternal Assessment
Following the primary survey of the patient and performance of life-saving measures, the secondary survey is initiated. This consists of obtaining a thorough history, including an obstetric history. An accurate prenatal history is crucial because comorbid factors such as pregnancy-induced hypertension, diabetes mellitus, and congenital heart disease may alter management decisions. Furthermore, a history of preterm labor, placental abruption, or placenta previa puts the patient at increased risk for the recurrence of these conditions. The obstetric history includes the date of the last menstrual period, expected date of delivery, and date of the first perception of fetal movement, and any problems or complications of the current and previous pregnancies. Whenever possible, the obstetrical team should be immediately notified and respond to the trauma room for patients in their second or third trimester of pregnancy.
During the secondary survey, appropriate x-rays should be ordered as during any trauma evaluation, shielding the uterus whenever possible (see below). The Focused Assessment with Sonography in Trauma (FAST) examination (see Chapter 16) is strongly recommended during the secondary survey to detect pericardial or peritoneal fluid in the mother. Although there is some debate on the sensitivity of ultrasound in this setting, most report an 80% sensitivity and a 100% specificity in detecting fluid using the FAST examination during pregnancy.26 A small amount of free fluid in the pelvis may be normal during pregnancy, but this trace amount (7–21 mL) is too small to be detected during a routine transabdominal ultrasound examanition.27 Therefore, any amount of fluid seen on the FAST examination should be considered pathologic even during pregnancy.
As part of the abdominal examination, determination of the uterine size provides an approximation of gestational age and fetal maturity. Measurement of fundal height is a rapid method for estimating fetal age. If, for example, the most superior part of the fundus is palpated at the umbilicus, the fetal age is estimated to be 20 weeks. A discrepancy between dates and uterine size may result from a ruptured uterus or intrauterine hemorrhage. Determination of fetal age and fetal maturity is an important factor in the decision matrix regarding early delivery. In general, a 25-week-old fetus is considered viable if given neonatal intensive care. Fig. 37-1 contains a helpful algorithm summarizing the initial evaluation of the injured pregnant patient.
Algorithm for the initial evaluation and resuscitation of the injured mother and fetus.
Evaluation of the Fetal–Placental Unit
Evaluation of the state of the pregnancy focuses on the following: (a) vaginal bleeding; (b) ruptured membranes (amniotic sac); (c) a bulging perineum; (d) the presence of contractions; and (e) an abnormal fetal heart rate (FHR) and rhythm. These five conditions indicate the acute status of the pregnancy. Vaginal bleeding prior to labor is abnormal and may indicate premature cervical dilation, early labor, placental abruption (separation of the placenta from the uterine wall), or placenta previa (location of the placenta over a portion of the cervical os). A ruptured amniotic sac should be suspected when cloudy white or green fluid is observed coming from the cervical os or perineum. The presence of amniotic fluid can be confirmed by the change in color of nitrazine paper from blue–green to deep blue when the fluid is tested. Rupture of the amniotic sac is significant because of the potential for infection and prolapse of the umbilical cord, the latter being an obstetric emergency requiring immediate cesarean section. Bloody amniotic fluid is an indication of premature separation of the placenta (placental abruption) or placenta previa. In the presence of known or continuous meconium staining (green amniotic fluid), continuous electronic fetal monitoring is necessary. A bulging perineum is caused by pressure from a presenting part of the fetus. If this occurs during the first trimester, spontaneous abortion may be imminent.
Assessment of the pattern of uterine contraction is accomplished by resting the hand on the fundus and determining the frequency, duration, and intensity of contractions. Contractions are usually rated as mild, moderate, or strong. Strong contractions are associated with true labor, and assessment for their presence is important so that appropriate preparation can be made for delivery and resuscitation of the neonate if necessary.
The Kleihauer–Betke (KB) test is used after maternal injury to identify fetal blood in the maternal circulation (i.e., fetomaternal transfusion). Adult hemoglobin (HbA) is eluted in the presence of an acidic buffer, whereas fetal hemoglobin (HbF) is resistant to elution. Fetal cells containing HbF are stained with erythrosine, whereas maternal cells containing HbA fail to stain and remain as “ghost cells” in the peripheral smear. Because the KB test can determine the risk of isosensitization in Rh-negative gravidas, it is recommended for detecting imminent fetal exsanguination in injured pregnant patients who are Rh-negative in the second or third trimester. If positive, the KB test should be repeated after 24 hours to identify ongoing fetomaternal hemorrhage. The initial dose of Rh-immune globulin is 300 μg, with an additional 300 μg given for every 30 mL of fetomaternal transfusion estimated by the KB test. Although the KB test is a very sensitive marker for even a small amount of fetomaternal transfusion, its clinical utility in Rh-positive mothers is uncertain.28 Indeed, the usefulness of the KB test after injury has been challenged recently by several authors. Authors from the R Adams Cowley Shock Trauma Center in Baltimore reported that among 46 injured women who were KB-positive on admission, 44 had documented contractions.29 In that study, KB testing accurately predicted the risk of preterm labor after maternal trauma, whereas clinical assessment was insensitive in identifying women at risk for this complication. On the other hand, a recent study from Cincinnati documented that 5% of low-risk women had a positive KB test, compared to only 2.6% of injured patients.30 None of these positive results were associated with a clinical abruption or fetal distress. The authors concluded that the presence of a positive KB test alone does not necessarily indicate pathologic fetal–maternal hemorrhage in patients with trauma, and that its routine use after injury should be abandoned.31
Unfortunately, direct assessment of the fetus following trauma is somewhat limited. Currently, the most valuable information regarding fetal viability can be obtained by a combination of monitoring of the FHR and ultrasound imaging. Fetal heart tones can be detected with a Doppler device around the 12th week of pregnancy. The normal FHR is between 120 and 160 beats/min. Because the fetal stroke volume is fixed, the initial response to the stress of hypoxia or hypotension is tachycardia. Severe hypoxia in the fetus, however, is associated with bradycardia (FHR <120 beats/min) and should be recognized as fetal distress, demanding immediate attention. Initial FHR monitoring of all pregnant patients with potentially viable pregnancies (i.e., those that would survive if emergency delivery was required) is indicated, even following relatively minor abdominal trauma. This monitoring is best accomplished using cardiotocographic (CTM) devices, which record both uterine contractions and FHR. A lack of variability in heart rate may also indicate fetal distress, and if there is no response to conservative measures such as fluid administration, increasing inspired oxygen, or change in maternal position, an emergency delivery should be considered (Fig. 37-2).
(A) Cardiotocographic strip demonstrating poor beat-to-beat variability in the fetus. (B) Return of beat-to-beat variability after resuscitation; variable decelerations with uterine contractions are within normal limits.
Blunt trauma to the abdomen can result in uterine rupture, but this event is uncommon, unlikely to be missed, and usually rapidly fatal for the fetus. A much more common event is placental separation from the uterus as the result of the shearing forces following blunt injury. This separation is termed placental abruption. Major cases of placental abruption (i.e., >50% separation) are uniformly fatal for the fetus, but more minor cases may initially go undetected. Vaginal bleeding is an unreliable sign of placental abruptions, occurring in only 35% of cases.25 On the other hand, in patients with placental abruption following trauma, CTM will detect early fetal distress, often manifested as a decelerated heart rate associated with uterine contractions. Most cases of placental abruption become evident within several hours of trauma, although late cases have been reported.25,32,33 A minimum of 24 hours of CTM is recommended for patients with frequent uterine activity (≥6 contractions per hour), abdominal or uterine tenderness, vaginal bleeding, or hypotension.34 A study of 271 pregnant patients who had sustained blunt trauma identified the following risk factors for fetal loss: ejections, motorcycle and pedestrian collisions, maternal tachycardia, abnormal FHR, lack of restraints, Injury Severity Score (ISS) >9, gestational age >35 weeks, and a history of assaults.35 Patients with any of these risk factors should be monitored for at least 24 hours. In the absence of these factors, asymptomatic trauma patients should undergo at least 6 hours of CTM prior to considering discharge. These patients should be counseled to observe for decreased fetal movement, vaginal bleeding, abdominal pain, or frequent uterine contractions, as partial placental lacerations have been reported to progress over time.36
Ultrasonography High-resolution real-time ultrasonography (US) has proven valuable for the assessment of fetal age and well-being, recognition and categorization of fetal abnormalities, and treatment of disease processes in the unborn patient. In the trauma setting, US is used primarily to identify acute problems that may be due to maternal events such as placental abruption, placenta previa, or cord prolapse. Although placental abruption is difficult to detect, US can accurately locate the lower margin of the placenta and its relation to the cervical os, hence demonstrating placenta previa.37 Additionally, it is routine to evaluate the fetus for gestational age, cardiac activity, and movement. In a study of 216 patients with high-risk pregnancies, fetal biophysical profile scores corresponded well with perinatal outcome.38 US findings consistent with uteroplacental injury may include oligohydramnios secondary to uterine injury or ruptured membranes. Oligohydramnios should be suspected if less than a 1-cm layer of amniotic fluid surrounds the fetus.
Radiographic Examination Following the secondary survey and the initial assessment of the fetus, appropriate diagnostic studies should be utilized to fully evaluate the extent of maternal injuries. Although there is much concern about radiation exposure during pregnancy, a diagnostic modality deemed necessary for maternal evaluation should not be withheld on the basis of its potential hazard to the fetus. There are three phases of radiation damage related to the gestational age of the fetus.39 During preimplantation and early implantation (less than 3 weeks’ gestational age), exposure to radiation can result in death of the embryo. During organogenesis (from 316 weeks’ gestation), radiation can damage the developing fetal tube and results in the associated anomalies of exencephaly, dysraphism, single cerebral ventricle, hydrocephaly, and the hypoplastic brain syndrome. Skeletal and genital abnormalities, retinal pigmentation, and cataracts are associated with radiation received during the third and eleventh weeks of gestation. After 16 weeks, neurologic defects are the most common complications of radiation exposure, due to the sensitivity of neuroblasts, which persist in the human embryo from 16 days postconception to about 2 weeks after birth.39 Prenatal x-ray exposure may also be associated with the later development of childhood cancers.40
Most of the human data on exposure to radiation is based on the large doses received in an atomic bomb blast (which includes neutrons and gamma ray), rather than on doses applied during normal diagnostic (x-ray) studies. The rad is the unit of measurement for absorbed radiation and corresponds to an energy transfer of 100 erg/g of tissue. Absorbed radiation is expressed in Gray (Gy) units, with 1 Gy equal to 100 rad. The dose to the uterus/fetus from x-ray procedures depends on several factors, including the x-ray tube potential, the current, the exposure time, the size of the patient, the type of procedure, the source-to-film distance, and the type of x-ray generator (Table 37-2). It is estimated that the fetal radiation dose without shielding is 30% of that to the mother.
Table 37-2 Estimated Fetal Exposure from Some Common Radiologic Procedures |Favorite Table|Download (.pdf)
Table 37-2 Estimated Fetal Exposure from Some Common Radiologic Procedures
|Chest x-ray (anteroposterior/lateral)||0.02–0.07 mrad|
|Abdominal plain x-ray||100 mrad|
|Hip x-ray (single view)||200 mrad|
|Head or chest CT||<1 rad|
|Abdomen and lumbar spine CT||3.5 rad|
|Pelvis CT||0.25–1.5 rad|
|Anteroposterior pelvis||0.04 rad|
|Complete spine series||0.37 rad|
The American College of Obstetricians and Gynecologists (ACOG) has produced a consensus statement on the use of diagnostic imaging during pregnancy.41 The authors emphasize the fact that most diagnostic radiologic procedures are associated with little, if any, known significant fetal risk. Specifically, exposure of the fetus to less than 5 rad has not been associated with an increase in fetal anomalies or pregnancy loss. A plain x-ray generally exposes the fetus to very little radiation, and the uterus is shielded for nonpelvic procedures during pregnancy. With the exception of a barium enema or small bowel series, most fluoroscopic examinations result in fetal exposure of just millirads. Radiation exposure from CT varies depending on the number and spacing of adjacent image sections (see Table 37-2). CT pelvimetry can result in fetal exposures as high as 1.5 rad but can be reduced by using a low-exposure technique as outlined by Moore and Shearer.42 Radiation exposure using helical CT is affected by slice thickness, the number of cuts obtained, and the pitch (a ratio defined as the distance the couch travels during one 360° rotation divided by the section thickness). Thus, CT can be used, when indicated to diagnose both maternal and fetal injuries as well as evaluating the placenta.
Table 37-3 Postmortem Cesarean Section |Favorite Table|Download (.pdf)
Table 37-3 Postmortem Cesarean Section
|Predictors of Successful Fetal Outcome Following Postmortem Cesarean Section|
Duration of gestation
Fetal viability generally is defined as 26–28 weeks’ gestation. This corresponds to a fundal height of approximately 26–28 cm above the pubis and/or uterus, halfway between the umbilicus and costal margin. At this age, the fetus, under optimal conditions, has a 40–70% estimated chance of survival without major handicap; therefore, cesarean section is indicated shortly after maternal death
Time between maternal death and delivery
- <5 min, excellent
- 5–10 min, good
- 10–15 min, fair
- 15–20 min, poor
- 20–25 min, unlikely
Complete the CPR sequence
Make a vertical midline incision through the abdominal layers into the uterus
Remove the fetus from the uterine cavity, clamp the cord, and hand the neonate to appropriate personnel for resuscitation
Remove the placenta
Continue CPR and assess for maternal signs of life; maternal survival is still possible after the uterus has been emptied and the supine hypotension syndrome has been resolved.
In summary, the ACOG Committee recommends the following:
- Women should be counseled that x-ray exposure from a single diagnostic procedure does not result in harmful fetal effects. Exposure to less than 5 rads is not harmful to the fetus or the pregnancy.
- Concern about possible effects of high-dose ionizing radiation should not prevent medically indicated diagnostic x-ray procedures from being performed during pregnancy.
- Other imaging procedures not associated with ionizing radiation, such as US or magnetic resonance imaging, which are not associated with known adverse fetal effects, should be utilized when appropriate.
- Consultation with an expert in dosimetry calculation may be helpful when multiple diagnostic x-rays are required.41
For a more complete review of the effects of ionizing radiation in pregnancy, readers are referred to the recent publications by De Santis et al.43 and Mann et al.44 For the injured patient, the following guidelines are suggested:
The minimum number of x-rays should be ordered to obtain the maximum information. Careful planning prevents duplication.
The patient’s abdomen should be shielded with a lead apron. This reduces fetal exposure by a factor of 8.
When many x-rays are required over a long period, a thermoluminescent dosimeter or “radiation badge” may be attached to the patient to serve as a guide to the dosage of radiation delivered. This is particularly valuable for the critically ill patient, who may have a prolonged stay in the intensive care unit.