Trauma remains the leading cause of nonobstetric morbidity and
mortality in pregnant women. After traumatic events (particularly
apparently minor ones), the severity of maternal injuries may be
a poor predictor of fetal distress and outcome. Trauma during pregnancy
is associated with an increased risk of preterm labor, abruptio
placentae, fetomaternal hemorrhage, and pregnancy loss. Achieving
successful outcomes for both mother and fetus requires a collaborative
effort by the prehospital provider, emergency physician, trauma
surgeon, obstetrician, and neonatologist.
Trauma during pregnancy is common. One study estimated that 32,810 pregnant
women sustain injuries in motor vehicle crashes every year in the
U.S., a rate of 9 per 1000 live births.1
The most common cause of blunt abdominal trauma is motor vehicle collisions,
which account for up to 70% of acute injuries. This is
followed by falls and direct assault in decreasing order of frequency.2 The
incidence of falls appears to increase with the advancement of pregnancy, presumably
due to alterations in maternal balance and coordination. Even minor
abdominal trauma can result in fetal demise. Penetrating injuries
are less common than blunt trauma during pregnancy.
Physiologic changes in pregnancy are discussed
in detail in Chapter 103, Normal Pregnancy.
In addition to the normal physiologic changes associated with pregnancy,
non–trauma-related complications of pregnancy must be considered.
Conditions such as pregnancy-induced hypertension, placenta previa, preeclampsia,
and eclampsia may significantly alter the presentation and complicate
evaluation and treatment in the setting of trauma (see Chapter 104, Emergencies after 20 Weeks of Pregnancy and the Postpartum Period).
Maternal blood volume begins to expand at approximately
week 10 of gestation and peaks at about a 45% increase
from baseline at week 28, which results in hypervolemia. Red cell
mass increases to a lesser extent, which leads to the relative physiologic
anemia of pregnancy. Cardiac output is increased by 1.0 to 1.5 L/min
at week 10 of pregnancy and remains elevated until the end of pregnancy.
Heart rate in the mother is generally increased by 10 to 20 beats/min
in the second trimester, accompanied by decreases in systolic and
diastolic blood pressures of 10 to 15 mm Hg.
The relative hypervolemic state can mislead the
clinician during maternal resuscitation after trauma and make clinical
findings difficult to interpret. A pregnant patient may lose
30% to 35% of circulating blood volume before
manifesting hypotension or clinical signs of shock. Uterine
arteries constrict, which results in diminished fetal blood flow and
tissue oxygenation before significant evidence of maternal hypovolemia
After week 12 of gestation, the uterus
becomes an intra-abdominal organ, which removes it from the relative
protection of the maternal pelvis and makes it more susceptible
to direct injuries. The bladder also moves anteriorly into
the abdomen in the third trimester of pregnancy, which increases
its vulnerability. Uterine blood flow may increase to upward of
600 mL/min, so that severe maternal hemorrhage from uterine ...