Trauma is the leading cause of nonobstetric morbidity and mortality in pregnant women. Motor vehicle collisions followed by falls and domestic violence are the most common causes of trauma in pregnancy and fetal survival is highly dependent on maternal stabilization.
Physiologic changes of pregnancy make it difficult to determine the severity of injury. Heart rate increases 10 to 20 beats per minute in the second trimester while systolic and diastolic blood pressures drop 10 to 15 mm Hg. Blood volume can increase by 45%, but red cell mass increases to a lesser extent, leading to a physiologic anemia of pregnancy. It may be difficult to determine whether tachycardia, hypotension, or anemia is due to blood loss or normal physiologic changes. Due to the relative hypervolemic state, the patient may lose 30% to 35% of blood volume before manifesting signs of shock. Pulmonary changes in pregnancy include elevation of the diaphragm and a decrease in residual volume and function residual capacity. Tidal volume increases, resulting in hyperventilation with associated respiratory alkalosis. However, renal compensation causes the serum pH to remain unchanged. Gastric emptying is also delayed, which places the pregnant trauma patient at a higher risk of aspiration.
The anatomic changes in pregnancy affect the types of injuries that are typically seen in the mother. Splenic injury remains the most common cause of abdominal hemorrhage in the pregnant trauma patient. After the 12th week of gestation, the enlarging uterus emerges from the pelvis and by 20 weeks reaches the level of the umbilicus. Uterine blood flow increases, making severe maternal hemorrhage from uterine trauma more likely. The uterus also can compress the inferior vena cava when the patient is supine, leading to the “supine hypotension syndrome.” As pregnancy progresses, the small intestines are pushed cephalad, which causes an increased likelihood of injury in penetrating trauma to the upper abdomen. The bladder moves into the abdomen in the third trimester, thereby increasing its susceptibility to injury.
Abdominal trauma affects not only the mother but also the fetus. Fetal injuries are more likely to be seen in the third trimester and are often associated with pelvic fractures or penetrating trauma in the mother. Uterine rupture is rare but is associated with a very high fetal mortality rate. More common complications of trauma include uterine irritability, preterm labor, and placental abruption. Classically, the mother will demonstrate abdominal pain, vaginal bleeding, and uterine contractions. Fetal–maternal hemorrhage occurs in more than 30% of cases of significant trauma and may result in rhesus (Rh) isoimmunization of Rh-negative women.
DIAGNOSIS AND DIFFERENTIAL
Maternal stability and survival offer the best chance for fetal well-being, and no critical interventions or diagnostic procedures should be withheld out of concern for potential adverse effects to the fetus. The initial sequence of trauma resuscitation is unchanged. Special attention should be directed to the ...