Trauma in Pregnancy
INTRODUCTION
Every emergency room (ER) doctor or nurse knows the feeling of dread when the EMS radio announces the imminent arrival of a pregnant patient involved in a serious motor vehicle accident (MVA). Optimal care for both the woman and fetus requires the coordination of services from the prehospital providers, the ER professionals, the trauma surgeon, the obstetrician, and the neonatologist. This coordination is initiated and led by the ER practitioner. Trauma occurs in 1 out of every 12 pregnancies. The etiology of trauma in pregnancy is MVAs (55%), followed by falls (22%), assaults (22%), and burns (1%). Fetal deaths are caused by MVAs (82%), firearm injuries (6%), and falls (3%). Physical abuse occurs in 1% to 20% of pregnancies depending on the study. Trauma is the leading cause of nonobstetric deaths.
PREVENTION
Despite case reports of uterine rupture with proper seat belt use, restrained pregnant patients likely have better outcomes after MVAs compared with unrestrained patients.
To any EM practitioner who has witnessed the type of injuries unrestrained patients can sustain in an MVA, this makes intuitive sense.
Current American College of Obstetricians and Gynecologists recommendations state that seat belts should be used throughout pregnancy with the lap portion placed under the uterus and across the superior iliac spines and pubic symphysis.
The shoulder portion should be placed between the breasts.
A pregnancy-mimicking crash test dummy demonstrated that placement of the lap belt over the uterus resulted in a three-to-four-fold increase in forces transmitted to the “fetus.” Airbag deployment does not appear to increase maternal injury.
PHYSIOLOGIC CHANGES IN PREGNANCY
Many of the normal physiologic changes in pregnancy can affect maternal injury patterns and her body’s response to them.
The uterus becomes an intra-abdominal organ after the 12th week, leaving the protective cocoon of the pelvis.
As the uterus enlarges, it draws the bladder into the abdomen as well, increasing its potential for injury.
Bowel is also superiorly displaced and covered by the enlarging uterus, decreasing its risk for injury, especially in penetrating trauma.
Maternal heart rate increases by 10 to 15 beats/min, while the systolic blood pressure drops by 5 to 10 mm Hg, and diastolic blood pressure drops by 10 to 15 mm Hg.
Maternal minute ventilation is hormonally increased leading to PCO 2 values of approximately 30 mm Hg. The kidneys compensate by lowering the serum bicarbonate to 17 to 22 mEq/L.
In the third trimester, the enlarging uterus elevates the diaphragm by up to 4 cm, causing an enlarged cardiac shadow, and a wider mediastinum.
Maternal blood volume changes dramatically during pregnancy. Plasma volume increases by roughly 50%, while red blood cell (RBC) mass increases by 20% to 30%. This leads to an entity known as anemia of pregnancy with hematocrit values in the low 30s.
Uterine blood flow increases to approximately 600 mL/min, which can lead to catastrophic hemorrhage in the case of uterine injury.
PREHOSPITAL CARE
The routine ABCs of trauma resuscitation are still followed.
A pregnant patient’s body will shift blood away from the placenta during periods of hypovolemia, so euvolemia and adequate oxygenation must be maintained. This is accomplished through two large-bore IVs, crystalloid, and supplemental oxygen.
A situation peculiar to pregnant patients beyond 18 weeks is supine hypotension. This occurs when the gravid uterus compresses the inferior vena cava. This can be alleviated by rolling the backboard 15 degrees to the left and then securing this position with blankets. Alternatively, the uterus can be manually shifted to the left.
If possible, the pregnant patient should be transported to a hospital that has the capability to care for the mother and to deliver and care for a distressed newborn even if the trauma seems innocuous.
Keep in mind that placental abruption can occur after a seemingly minor trauma.
