Trauma is the leading cause of nonobstetric morbidity and mortality in pregnant women. Fetal survival is highly dependent on stabilization of the mother.
Physiologic changes of pregnancy make determination of severity of injury problematic. Heart rate increases 10 to 20 beats/min 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 hypervolemic state, the patient may lose 30% to 35% of her blood volume before manifesting signs of shock. Pulmonary changes in pregnancy include elevation of the diaphragm and decreases in residual volume and function residual capacity. Tidal volume increases, resulting in hyperventilation with associated respiratory alkalosis. Renal compensation causes the serum pH to remain unchanged.
Anatomic changes with pregnancy affect the types of injuries seen in the mother. After week 12 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, increasing their likelihood of injury in penetrating trauma to the upper abdomen. Decreased intestinal motility is associated with gastroesophageal reflux, thus predisposing the patient to vomiting and aspiration. The bladder moves into the abdomen in the third trimester, thereby increasing its susceptibility to injury. Splenic injury remains the most common cause of abdominal hemorrhage in the pregnant trauma patient.
Abdominal trauma affects the fetus and the mother. Fetal injuries are more likely to be seen in the third trimester, often associated with pelvic fractures or penetrating trauma. Uterine rupture is rare but is associated with a very high fetal mortality rate. More common complications of trauma include preterm labor and abruptio placentae. Second only to maternal death, abruptio placentae is a common cause of fetal death. Classically, the mother will demonstrate abdominal pain, vaginal bleeding, uterine contractions, and signs of disseminated intravascular coagulation. Fetal–maternal hemorrhage occurs in more than 30% of cases of significant trauma and may result in rhesus (Rh) isoimmunization of Rh-negative women.
Because maternal stability and survival offer the best chance for fetal well-being, no critical interventions or diagnostic procedures are withheld out of concern for potential adverse effects to the fetus. The initial sequence of trauma resuscitation is unchanged. Direct special attention to the gravid abdomen, examining for evidence of injury, tenderness, or uterine contractions. If abdominal or pelvic trauma is suspected, perform a sterile pelvic examination to assess for genital trauma, vaginal bleeding, or ruptured amniotic membranes. Fluid with a pH of 7 in the vaginal ...