eMedicine Specialties > Emergency Medicine > Obstetrics & Gynecology

Pregnancy, Trauma

Author: Andrew K Chang, MD, Associate Professor, Department of Emergency Medicine, Albert Einstein College of Medicine, Montefiore Medical Center
Contributor Information and Disclosures

Updated: Feb 3, 2009

Introduction

Background

The pregnant trauma patient presents a unique challenge because care must be provided for two patients—the mother and the fetus. Anatomic and physiologic changes in pregnancy can mask or mimic injury, making diagnosis of trauma-related problems difficult. Care of pregnant trauma patients with severe injuries often requires a multidisciplinary approach involving an emergency clinician, trauma surgeon, obstetrician, and neonatologist.

Pathophysiology

To evaluate the pregnant patient, the various physiologic changes that occur during pregnancy must be understood. Because balance and coordination are most adversely affected during the third trimester, the frequency of accidental injury is greatest during this period. Although the pregnant patient's blood pressure decreases during pregnancy, changes may not be as great as traditionally thought. Systolic blood pressure changes by only 2-4 mm Hg, while diastolic pressure decreases by 5-15 mm Hg in mid-trimester. In addition, the resting heart rate usually increases by only 10-15 beats per minute. Thus, tachycardia or hypotension in the pregnant trauma patient should not be attributed solely to the gravid state.

Physiologic anemia in pregnancy is due to a dilutional effect of plasma volume increasing by 50% but red blood cell volume increasing by only 18-30%. Thus, the average hematocrit level is 32-34% and is at its nadir around the 30th to 34th week of gestation. Because the average estimated blood loss is approximately 500 mL for a vaginal delivery and 1000 mL for a cesarean delivery, no change in hemodynamic parameters occurs because of these preemptive adaptations. The uterus, which grows from 70 g to 1000 g, enlarges into the peritoneal cavity after the 12th week of pregnancy. Although it now becomes more susceptible to injury, it also provides protection for other maternal abdominal organs such as the small bowel. The bladder is also moved into the abdomen by the uterus in the second and third trimesters, and the ureters become dilated (right > left). Gastrointestinal tract motility decreases.

Blood flow to the uterine arteries is normally maxillary vasodilated, so blood delivery to the uterus is maximal in the normal physiologic state. Maternal hypovolemia may result in vasoconstriction of the uterine vasculature. The third trimester fetus can adapt to a decrease in uterine blood flow and oxygen delivery by diverting blood distribution to the heart, brain, and adrenal glands. Because fetal hemoglobin has a greater affinity for oxygen than does adult hemoglobin, fetal oxygen consumption does not decrease until the delivery of oxygen is reduced by 50%. Thus, maternal shock may have a significant impact on the developing embryo/fetus. 

For further information, see Trauma and Pregnancy.

Frequency

United States

Six to seven percent of all pregnant women experience some sort of trauma, with the greatest frequency in the last trimester. Although usually accidental, the injuries are sometimes caused by intentional violence. Approximately 0.3-0.4% of pregnant women have traumatic injuries that require hospitalization.

Mortality/Morbidity

Trauma is the leading cause of maternal death, accounting for up to 46% of cases. Fetal death, however, is a more common occurrence than maternal death. 

Direct fetal injury is relatively uncommon because the maternal soft tissues, uterus, placenta, and amniotic fluid all tend to absorb and distribute the energy of the blow. The most common cause of fetal death is maternal shock, which is associated with a fetal mortality rate of 80%. This explains why efforts to assess fetal well-being are secondary to resuscitation of the mother.

Placental abruption is the second most common cause of fetal death, with fetal mortality rates as high as 30-68%. Placental abruption occurs when shearing forces lead to a separation of the rigid placenta from the elastic uterus. Up to 30-50% of patients with major traumatic injuries and as many as 5% of patients with minor injuries have placental abruption after trauma. Blunt injury in pregnancy does not appear to pose higher risk for death than it does in nonpregnant patients, with most deaths occurring as a result of either head injury or hemorrhage. 

Homicides (36%) and motor vehicle accounts (32%) are the most common injuries that result in death. Penetrating wounds injure the fetus in as many as 70% of third-trimester cases and cause maternal visceral injuries in 19% of cases.

Age

In one trauma center that treats more than 2,500 trauma patients per year, the mean age of pregnant trauma patients was 25 years, with a range of 14-45 years.

Clinical

History

Features of the patient's history may include the following:

• Mechanism
  • Direct abdominal trauma
  • Weapons
  • Seatbelt use, proper or improper (The American College of Obstetrics and Gynecology emphasizes that both the lap belt and shoulder harness be worn with the lap belt passing below the abdomen and over the anterior superior iliac spine and symphysis pubis and the shoulder harness passing between the patient's breasts).
• Last menstrual period (LMP) and estimated date of confinement (EDC)
• Uterine contractions
• Fetal movement
• Premature rupture of membranes
• Vaginal bleeding
• History of depression, substance abuse, or several ED visits (These factors may suggest intimate partner violence, which is not dependent on age, race, marital status, or socioeconomic class.) A review of 13 studies found the prevalence of intimate partner violence to range from 0.5-20.1%.¹

Physical

Primary and secondary trauma surveys should be performed as per usual, as the hemodynamic and ventilatory well-being of the patient are the most important factors in determining the fetus' outcome in a critically injured pregnant patient. The secondary survey should also include the following:

• Abdominal examination
  • Inspect for ecchymoses, especially across the lower abdomen, which may indicate a possible seatbelt injury.
  • Palpate for uterine contractions or tenderness.
  • Gestational age can be estimated by the size of the gravid uterus. In general, when the fundal height reaches the umbilicus, gestational age can be estimated at 20 weeks. Once above the umbilicus, the fundal height in centimeters measured from the symphysis pubis correlates well with gestational age.
  • Fetal heart tones can be assessed with Doppler examination or ultrasonography.
  • Rebound tenderness and guarding may be less apparent in advanced gestation, making clinical diagnosis of hemoperitoneum potentially less reliable because peritoneal stretching in the third trimester decreases the density of afferent pain fibers, thereby muting peritoneal signs.
• Sterile speculum examination before bimanual examination
  • Perform these in the absence of vaginal bleeding.
  • Test the fluid for pH and ferning. A pH of 7 indicates amniotic fluid. Vaginal secretions are more acidic, with a pH around 5.
  • Examine for vaginal lacerations, which may signify an open pelvic fracture.
  • Look for bone fragments in the vagina, which signify an open pelvic fracture.
• Bimanual examination
  • In general, the obstetrician should perform this examination.
  • It should be performed in a setting where emergency cesarean delivery can be performed.
• Evaluation for possible domestic violence
  • Ecchymoses of the breasts, abdomen, and upper extremities may be present.
  • Injuries at more than one site in varying stages of healing may be observed.

Causes

Causes of traumatic injuries in pregnancy are similar to those in the general population; blunt injury trauma is the most common cause.  

• Motor vehicle accidents (MVAs) account for 49% of injuries.
• Falls account for 25% of injuries (may be related to physiologic changes that result in loss of balance).
• Assaults account for 18% of injuries.
• Guns account for 4% of injuries.
• Burns account for 1% of injuries.
• Intimate partner violence

Risk factors for trauma in pregnancy include simply pregnancy itself, younger age, drug use, alcohol use, and history of intimate partner violence.

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