Pregnancy Trauma

Updated: Dec 03, 2020
  • Author: Andrew K Chang, MD, MS; Chief Editor: Bruce M Lo, MD, MBA, CPE, RDMS, FACEP, FAAEM, FACHE  more...
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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.

A systematic review on this topic noted that the available literature is characterized by severe limitations, including retrospective design, widely variable outcomes, and ascertainment bias. [1] The review did conclude that the major determinant of obstetrical outcomes after trauma is the severity of injury and that motor vehicle accidents and domestic violence/intimate partner violence are the most common mechanisms of traumatic injury during pregnancy, with substance abuse being a common accompaniment to these forms of trauma.

For more information, see the slideshow Don't Bump the Bump: Trauma in Pregnancy.



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.



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.

The prevalence of domestic and intimate partner violence across various populations has been evaluated extensively, with more than 60 studies from more than 20 countries reporting a frequency during pregnancy ranging from 1-57%. One explanation for this wide range is the inclusion of emotional, verbal, and/or physical violence within the definition of domestic violence/intimate partner violence in some studies.

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



United States data

Six to eight percent of all pregnant women experience some sort of trauma, with the greatest frequency in the last trimester. [2] 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.

Falls caused over half of reported injuries during pregnancy; 51.6% and 9.5% of reported injuries were intentionally inflicted. [3] Mothers who reported an injury during pregnancy were more likely to be older than 18 years and less likely to be age 30 years or older. These mothers were more likely to use alcohol during pregnancy, to smoke during pregnancy, to have epilepsy, and to be employed than mothers who did not report an injury.

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.




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.

In a retrospective, population-based, matched cohort Canadian study (2006-2010) that evaluated the outcomes of cardiopulmonary resuscitation (CPR) in pregnant women in the emergency department (ED), the investigators noted that trauma status was a significant predictor of outcome in pregnancy. [4]  Gravid females had a better overall survival (36.9%) compared to nonpregnant women (25.9%), and when no trauma was involved in women requiring CPR, the odds of surviving CPR were significantly better in pregnant women than their nonpregnant counterparts. However, in the presence of trauma, there was no significant difference between the groups. [4]

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.

Fetal mortality and overall maternal morbidity remains exceedingly high (73% and 66%, respectively) following penetrating abdominal injury. [5]

Homicides (36%) and motor vehicle accidents (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.

In a retrospective review (2009-2012) of maternal-fetal outcomes following motor vehicle injury in 728 Kuwaiti pregnant women, investigators noted important causes of adverse outcomes in 648 women (89%) included abruption placenta (58.8%), preterm labor (40%), and uterine rupture (1.6%). [6]  Maternal mortality occurred in 100 (13.7%) and fetal mortality in 78 (10.7%). Only 44.8% of prenatal visits included prenatal care provider counseling regarding the use of seat belts. Women wearing seat belts during the accidents had minor injuries/sprains. [6]

Penetrating injury has a perinatal mortality rate of 40-70%, although the maternal mortality rate is less than that in the nonpregnant patient because of the protective effects of the large, muscular uterus on the maternal visceral organs.

In one urban study, violence accounted for 57% of maternal deaths (48% homicides, 9% suicides). Investigators in another study reported a 7% maternal mortality rate in serious automobile injuries and a 14% injury rate in surviving mothers.


Complications of pregnancy trauma include the following:

  • Exsanguination: Dramatic increases in uterine blood flow (60 to 600 mL/min) may result in rapid exsanguination if there is avulsion of the uterine vessels or rupture of the uterus.

  • Retroperitoneal hemorrhage: A common complication of pelvic fracture due to the tremendous increase in vascularity resulting from pregnancy.

  • Uterine rupture: Enlargement of the uterus makes it susceptible to direct abdominal trauma. This rare complication is estimated to complicate 0.6% of traumatic injury. Uterine rupture is associated with a fetal mortality rate approaching 100%. Maternal mortality of 10% is usually a result of associated injuries.

  • Rupture of amniotic membranes can lead to chorioamnionitis, preterm labor, and cord prolapse.

  • Amniotic fluid embolism (may lead to acute respiratory distress syndrome)

Placental abruption

Placental abruption is the most feared complication in cases of trauma. It occurs in 38-66% of major injuries and in 2-4% of minor injuries. It is the most common cause of fetal death when the mother survives the trauma. Placental abruption may be delayed for as long as 24-48 hours after the traumatic incident.

Diagnosis is made with 2 of the following 3 criteria:

  • Tense abdomen with uterine hypotonia

  • Maternal hypertension or hypotension

  • Ultrasonographic evidence of abruptio

Fetal distress is the most reliable indicator of active or impending abruption.

Ultrasonography is an insensitive tool and causes more than 50% of abruptions to be missed. Amniocentesis can be used to make the ultimate diagnosis in desperate situations.

Abruption can lead to consumptive coagulopathy. Fetal injury is the leading cause of fetal death in cases of maternal death. Direct fetal trauma is rare because of the protection from the uterus and amniotic fluid.

Fetomaternal hemorrhage

Historically, fetomaternal hemorrhage has been reported to occur in 9-30% of cases. However, one study of 151 women found an incidence of only 2.6%, which is similar to that of the general population.