Fetal Trauma from Motor Vehicle Collisions

>“Trauma is more likely to cause maternal death than any other medical complication of pregnancy.”

“Trauma is more likely to cause maternal death than any other medical complication of pregnancy.” 1

Six to seven percent of pregnant women experience trauma during pregnancy. When we’re responding to a pregnant woman who has experienced some form of trauma, two patients require our care: the mother and the fetus. EMS providers need to be aware of anatomical and physiological changes in pregnancy that can mask or mimic injury, which complicates assessment of the pregnant trauma patient.2

Although trauma is the leading cause of non-obstetric maternal death, less than one-half percent of pregnant women with traumatic injuries require hospitalization.2 Motor vehicle collisions are the leading cause of injury during pregnancy, accounting for 60% of injuries. Falls and physical abuse account for much of the remainder.2 Although any cause of blunt trauma—falls, physical abuse, collision—can have adverse impacts on the mother or fetus, motor vehicle collisions cause the most severe maternal injuries and fetal death.3

This article will review pregnancy anatomy and physiology, describe fetal trauma injuries, discuss assessment and treatment of maternal trauma, review components of fetal assessment and discuss strategies to prevent fetal trauma from motor vehicle collisions.

Pregnancy Anatomy

The uterus, a muscular organ, grows from a volume of 5 ml to 5 liters during pregnancy.4 In the first trimester, the uterus is still low in the abdomen and surrounded by the pelvis. In the second and third trimesters, it grows upward and outward, losing the protection of the pelvic ring and displacing other abdominal organs.4 The fetus is still relatively protected by the shock-absorbing properties of the amniotic fluid.4 The placenta is a vascular organ that exchanges nutrients and oxygen for metabolic waste with the fetus. The loose attachment of the placenta to the wall of the uterus is weaker than either of the two tissues.4

The gestation age of the fetus is split into three trimesters. From conception to the end of the first trimester, the pregnant woman experiences dramatic physical changes. Her blood volume increases, her breasts enlarge and she is often fatigued. Meanwhile, the fetus is growing to a weight of a few ounces, is moving spontaneously, and a heartbeat is audible with a Doppler ultrasound.5

During the second trimester, maternal blood volume has increased by 30%–40%. Cardiac output increases from one liter per minute to 6–7 liters per minute. One-sixth of maternal blood volume is in the placenta. Trauma that causes a placental laceration will lead to a quick and severe loss of blood.5 The mother is aware of fetal movement and experiences diminished agility from her shifting center of gravity and weight gain.

The expanding uterus grows into the peritoneal cavity after the 12th week of pregnancy. While the uterus is now more susceptible to injury, it offers some protection to other maternal organs, like the small intestine.2 The bladder is the most susceptible to damage from trauma since it is forced upward by the uterus.2, 5 The fetus is increasing in length and weight. By 20 weeks, the heartbeat can be auscultated with a stethoscope. Twenty- four to 25 weeks is considered the practical low-end age for out-of-uterus viability or survival.

The risk of accidental injury is greatest in the third trimester. Balance and coordination suffer greatly.2 This is when most falls and motor vehicle collisions occur. The fetus grows to its birth size and weight and is kicking actively.

Blood pressure does not change as significantly as once thought. A change of 2–4 mmHg for the systolic pressure and 5–15 mmHg for the diastolic pressure is normal. The mother’s resting heart rate increases by 10–15 beats per minute during pregnancy.2 Never discount tachycardia. During assessment, tachycardia and low blood pressure are not just caused by the pregnancy, but could be caused by blood loss.2

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