Chapter 43 Obstetric Trauma

Epidemiology and Priorities of Care

Five to ten percent of gravid women will sustain an injury for which they seek medical care.^1,² Fortunately, most cases involve minor or moderate trauma, but life-threatening injuries complicate 3 in 1000 pregnancies.³ As is true for nonpregnant women in their childbearing years, motor vehicle crashes are the primary mechanism of maternofetal trauma for pregnant women as well. Falls are the second most common cause of injury in pregnant patients.^1,² Pregnancy is a time of increased interpersonal stress, which puts women at risk for abuse. The frequency of intimate partner violence during pregnancy is difficult to establish but has been estimated to be between 1.2% and 24%.⁴ Following major trauma, the obstetric patient has about the same mortality rate as a nonpregnant woman with comparable wounds.⁵ However, the vulnerable fetus is five to seven times more likely to die from an injury than is its mother.¹

Care of the gravid trauma patient is complicated by the normal physiologic changes of pregnancy (Table 43-1) and by the presence of a second patient, the fetus. Pregnancy should never be permitted to divert attention from the rapid identification and appropriate management of maternal injuries.⁶ Vigorous maternal resuscitation remains the initial care priority and provides the fetus with the best possible chance of survival. Virtually all diagnostic procedures and interventions routinely employed in the care of the trauma patient are equally appropriate for management of the pregnant patient, with the addition of a few diagnostic procedures, modifications, and simple safety measures.

TABLE 43-1 MATERNAL CARDIOVASCULAR AND RESPIRATORY CHANGES DURING PREGNANCY

Assessment of the Obstetric Trauma Patient

Primary Assessment

The primary assessment of the pregnant trauma patient is conducted in the same manner and sequence as that of any other patient (see Chapter 35, Assessment and Stabilization of the Trauma Patient). Evaluation of airway, breathing, and circulation occurs simultaneously with interventions when a potentially life-threatening condition is identified. Importantly, the changes of pregnancy can mask normal physiologic responses to trauma, and these alterations must be considered carefully when managing the gravid patient. Table 43-2 summarizes the effects of these changes on the traumatized gravid patient.

TABLE 43-2 THE IMPACT OF NORMAL PHYSIOLOGIC CHANGES OF PREGNANCY ON THE TRAUMA PATIENT

Airway	The risk of aspiration is increased because of cardiac sphincter laxity, stomach compression, and gastric hypomotility. Consider liberal gastric tube placement. Endotracheal intubation is complicated by increased upper airway vascularity. Epistaxis and oral bleeding are potential problems.
Breathing	Pregnancy causes the patient to exist in a state of compensated respiratory alkalosis. Therefore arterial blood gases suggestive of shock (lactic acidosis) will not be evident until shock is advanced. High metabolic demands and diaphragm elevation (which reduces functional residual capacity) predispose the patient to hypoxia.
Circulation	The pregnant patient’s 40% increase in circulating volume can mask signs of shock until the patient has lost 1500 mL of blood. The pregnant patient (normally hot and flushed) may be slow to develop the cool, clammy skin characteristic of hemorrhagic shock. The physiologic anemia of pregnancy makes interpreting hemoglobin and hematocrit results difficult. The normal hypotension and tachycardia of pregnancy make interpreting vital signs difficult. After 20 weeks gestation, the combined weight of the fetus, uterus, placenta, and amniotic fluid will compress the vena cava, decreasing blood pressure and cardiac output when the patient is supine. In the presence of hypovolemia, the uterus (a nonvital organ) and the fetus inside it quickly become hypoperfused. Most clotting factor levels are elevated in pregnancy, making the pregnant patient prone to venous thromboembolic events and bleeding disorders. Because of a large circulating volume and hormonal changes, the pregnant patient does not concentrate urine efficiently and may produce normal amounts of urine output in the face of hypovolemia. Massively increased blood flow through the uterus predisposes the pregnant patient to major hemorrhage if the uterus or its vessels are damaged.