Trauma in pregnancy ranges from mild (a single fall from standing height or hitting the abdomen on an object such as an open desk drawer) to major (penetrating or high force blunt motor vehicle crash). Although infrequently encountered in the clinical setting, emergency medicine physicians, trauma surgeons and OBGYN's should aware of and prepared to manage a variety of complications associated with trauma in pregnancy. With sufficient knowledge of normal maternal physiology and potential pregnancy-related injury patterns, the physician facing a pregnant trauma victim will be better equipped to manage them, thus resulting in reduced morbidity and mortality.
Etiology of trauma in pregnancy may be multifactorial. The physics of the growing abdomen results in an imbalance which may lead to falls from standing or down stairs. Further, the clinician must maintain a high suspicion for non-accidental causes, either self-inflicted or other. The normal physiology of the pregnant mother complicates evaluation and management of trauma in pregnancy. The gravid uterus is particularly suspectible to penetrating and blunt trauma to the abdomen. Domestic violence increases during pregnancy, placing the mother and the fetus at high risk for injury. 
Anatomic and Physiologic Changes in Pregnancy. To be able to recognize abnormal vital signs and injuries in a pregnant patient, normal anatomic and physiologic changes in pregnancy must be understood. Multiple organ systems undergo changes during pregnancy, the major, pertinent systems are discussed herein.
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 by the third trimester becomes much less sensitive to peritoneal irritation. Even in patients with traumatic hemoperitoneum, they may not exhibit abdominal tenderness on examination due to the peritoneal stretching and insensitivity (AHC media, trauma reports. Current Concepts in the Management of the Pregnant Trauma Patient. Author: Dennis Hanlon, MD). The uterus eventually becomes the largest intraabdominal organ. Its walls become thin and susceptible to injury. Blood flow increases from a non-pregnant 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. Both the plasma volume and the red cell mass increase throughout pregnancy. Plasma volume doubles by the end of the third trimester, however, in much higher proportion than the red blood cell mass increase. This results in dilutional anemia of pregnancy. The normal hemoglobin is 10-14 grams per deciliter by the term. The liver becomes hypermetabolic, increasing production of coagulation factors and fibrinogen. With this production, the patient is now 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 is increased by 40%, leading to a 40% increase in MV. This leads to a lowered partial pressure of carbon dioxide (PCO) of 30 mmHg (normal values are in the range 35-45 mmHg), resulting in a chronically compensated respiratory alkalosis. This must be taken into account when evaluating a blood gas. The diaphragm is elevated by approximately 2-4 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 1-4: 1 denoting 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 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 3rd trimester elevates 15-20 beats per minute. The blood pressure goes down by 15-20 mmHg, however, returns to normal during the 3rd trimester. Any sign of hypotension should be evaluated immediately given this return to the normal level. It 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. There are injuries unique to pregnancy that must be considered in addition to these.
Premature Labor. Premature labor is defined as the presence of uterine contractions occurring at less than 36 weeks’ gestation (premature) accompanied by cervical changes (labor). Although trauma patients 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 hemorrhage. 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. It occurs in 1-5% of minor trauma. It is important to note that 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, in addition to the peritoneum being markedly insensitive given the massive stretching near term. Ultrasound may be helpful in the diagnosis but is not sensitive. If the ultrasound does not reveal abruption, the diagnosis is not ruled out. Regardless, toconometry is required for minimum 4 hours and may be extended by the obstetrical team for a multitude of reasons.
Amniotic Fluid Embolus. Uncommon and catastrophic, the pathophysiology of amniotic fluid embolus is currently poorly understood. The patient may present much like a massive pulmonary thrombotic embolus. There is no specific treatment for this entity, with exception of supportive care, intubation, vasopressors, and transfusion.
Uterine Rupture. Although a rare complication of trauma (0.06%), fetal mortality approaches 100% when present. It most often occurs in the 3rd 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; abdominal pain, distention (due to the unfolding of the fetus), palpable fetal parts, and shock. However, given the peritoneum's insensitivity in the 3rd trimester, there may be no pain present. High index of suspicion accompanied by prompt recognition is critical. Treatment is exploratory laparotomy, delivery of fetus and supportive care.
The standard trauma algorithim should be followed when evaluating a pregnant patient who has experienced trauma. This includes a primary, secondary, and tertiary survey. Attention should be paid to the vital signs as they change throughout normal pregnancy, see physiology and pathophysiology above.
In addition, the abdomen should be palpated to determine if the level of uterine height correlates with the estimated gestational age. At eight weeks, the uterus begins to enter the abdominal cavity, surfacing above the pubic symphysis. At 20 weeks, it approaches the level of the umbilicus. At this point, the uterus should grow at approximately one finger’s breadth until 40-weeks gestation. The uterus will reach the sternum at 36 weeks and then become lower as the fetal head engages in the pelvis. Deviation from these estimated levels should alert the clinician to an abnormality (uterine rupture or a preexisting condition such as multiple pregnancy or IUGR).
The Rh blood type of the patient should be sought. If maternal negative, there is a chance of developing iso-immunization and compromising further pregnancies. Rh Immunoglobulin (RhoGham) should be administered regardless of mechanism, including fall from standing, as maternal Rh sensitization will occur at 0.01-0.03 ml in 70% of Rh -ve patients. The dose of Rh Immunoglobulin is dependent upon the gestational age. At less than 12-weeks gestational age, 150mcg is indicated. At greater than 12 weeks, 300 mcg is indicated. The amount will need to be increased if fetomaternal hemorrhage is marked, in massive blunt force abdominal trauma. This is determined by the Klei-Hauer Betke test. The test is an acid elution assay on blood drawn from the maternal patient. After lysing cells with acid, it shows the amount of fetal blood in the maternal system. Note that this test has a threshold of 5 ml of maternal-fetal hemorrhage, but isoimmunization can occur at 0.01 ml. Therefore, this test should not be utilized to determine if, but rather how much, additional Rh Immunoglobulin is required.
Studies involving the teratogenic effects of radiation come mostly from the atomic bombings of Hiroshima and Nagasaki. At that time, malnutrition, a known teratogen, was widespread. As such, it is truly unclear what the safe dose of radiation is. However, currently, it is recommended that cumulative radiation doses do not exceed five rads in pregnancy. Abdominal and pelvic CT scans may exceed this recommended dose. Radiologic studies should not be withheld if indicated but should be used with caution and risk-benefit analysis. Alternative modalities should be sought if possible, including ultrasound. Consideration of dedicated upper abdomen CT with lower abdomen shielding should be done, as the most commonly injured organ remains the spleen, followed by the liver.
Advanced Trauma Life Support principles remain the same whether the patient is non-gravid or full-term. As always, taking care of the maternal patient will, in turn, take care of the fetus. In addition to standard resuscitation, there are some further recommendations.
Consultation with obstetrics is critical, and transfer to an obstetrical specialized trauma center is optimal if the patient is stable to be transferred.
The positioning of the patient to avoid or alleviate aortocaval compression syndrome, also known as a supine hypotensive syndrome, may be necessary. (See Aortocaval Compression Syndrome section for further information).
Preparation for precipitous delivery should occur before arrival when time allows.
Keep in mind that the maternal vital signs are less sensitive, and, as mentioned above, that the blood pressure returns to normal near term. If hypotension is present, then immediate investigation and treatment must ensue.
Lastly, consideration of perimortem caesarean section should be considered if maternal death occurs and pregnancy is viable (>23 weeks). See Cesarean, Perimortem section for further information.
Trauma during pregnancy is a commonly encountered disease state in the emergency department. Evaluating pregnant patients has significantly more medical, social and ethical considerations than non-pregnant patients. Hence, the management of pregnancy-related trauma usually involves an interprofessional group of health professionals. Trauma is the leading cause of death among young and middle aged adults. The key is education and preperation. Pregnant females should be told to wear a seat belt while in a car and avoid intense physical activities that pose a risk for falls. If there is domestic abuse in the home, the pregnant female should be encouraged to seek a safe shelter. Follow up by a social worker is key. At every prenatal visit, the obstetric nurse should emphasize the importance of safety. (Level V)
The outcomes of pregnant women who suffer trauma depend on the type and extent of trauma. Overall, penetrating trauma carries a fetal mortality rate of 30 to 80%, but the maternal mortality rates are low as the fetus protects the underlying organs of the pelvis. After blunt trauma, the morbidity and mortality depend on the severity of the force. Various series report morbidity rates of 5 to 45% in pregnant women suffering from blunt trauma. In many series, fetal demise is high when moderate to severe hemorrhage occurs. (Level V)
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