Pregnancy Trauma 

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



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.





Features of the pregnant 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% to 20.1%.[7] )

  • Infants with mothers who have childhood histories of abuse/neglect, particularly those with unresolved trauma and trauma-specific reflective function, appear to be disproportionately insecure and exhibit attachment disorganization.[8] Canadian investigators suggested that a strong concordance between mother and infant attachment may be indicative of intergenerational transmission of attachment in women with childhood histories of abuse/neglect and their infants.[8]

Physical Examination

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.



Differential Diagnoses



Laboratory Studies

Laboratory studies in the evaluation of the pregnant trauma patient may include the following:

  • Determination of CBC: Pregnancy-induced leukocytosis peaks to levels of 12,000-18,000 per cubic millimeter during the third trimester. During labor, levels as high as 25,000 per cubic millimeter may occur.

  • Determination of electrolyte and glucose levels

  • Blood typing and crossmatching

  • Rhesus (Rh) blood group determination (Administer Rho(D) immune globulin [RhoGAM] if the mother is Rh negative)

  • Urine pregnancy testing, if the status is unknown in a female of reproductive age with trauma

  • Urinalysis

  • Assessment of coagulation profile (Most coagulation factors rise throughout pregnancy, although laboratory values remain unchanged except for fibrinogen levels, which nearly double in value.)

  • Kleihauer-Betke testing: This test (an acid elution test in which adult hemoglobin is eliminated while fetal hemoglobin is resistant and hence stains) is used to detect fetal-to-maternal hemorrhage in excess of that which can be treated with a standard dose of 300 mcg of Rho(D) immune globulin (RhoGAM). In the event of fetal distress, a positive test result may indicate life-threatening hemorrhage in the fetal circulation. The test is useful in Rh-negative mothers because the standard dose of RhoGAM (300 mcg) covers only up to 15 mL of fetal red cells (30 mL of fetal whole blood). In major trauma, additional fetal red cells may come into contact with maternal blood, and the Kleihauer-Betke test helps to determine how much additional RhoGAM to administer. Although this test is usually only indicated for the Rh-negative pregnant patient with major trauma, some advocate its use in all patients as it may correlate with risk for preterm labor. However, it is neither sensitive nor specific for this outcomesoit should be used with caution or not at all.

  • Toxicology screening

  • D-dimer: Some obstetricians advocate use of D-dimer testing to help in determining the course of action for placental abruption.

  • Base deficit: In patients with blunt abdominal trauma, data show that base deficit is an early available important indicator to identify intra-abdominal injury.[9]

Imaging Studies

Radiologic examinations must be interpreted in the context of pregnancy-related changes. For example, increased AP diameters, mild pulmonary vascular cephalization, cardiomegaly, and a slightly widened mediastinum are seen in normal pregnancy. Similarly, pelvic radiographs show normal widening of the sacroiliac joints and symphysis pubis.

Radiologic examinations should not be deferred because of the presence of the fetus. Data about injury to the fetus secondary to diagnostic radiology are only suggestive. The 3 primary concerns are the following: radiation-induced cancer, loss of viability, and radiation-induced malformation (small head size). Usually, adverse effects are not expected until the dose is in the 50-100 mGy range (mGy = 0.1 rad). The acquisition of an anteroposterior pelvic radiograph delivers a 0.16-mGy dose to the fetus, while typical dose from CT scanning of the pelvis is approximately 20-50 mGy.

Data about radiation-induced cancer after in utero exposure suggest that risks for radiation-induced cancer fatality, in children younger than 14 years, may be on the order of 1 in 15,000 children. These results occur when each fetus is exposed to 1 mGy of radiation in utero during the second or third trimester. The risk ratio for a 50-mGy exposure is about 1:300. Risk of first-trimester exposure may be higher, but data are less specific.

Loss of viability of the fetus is possible if radiation exposure occurs within 2 weeks of conception. For most diagnostic abdominal examinations, this risk probably is less than 1%. All risk estimates related to this possibility at diagnostic dose levels are derived from animal data. Data suggest that, during this period, no increased risk of malformation exists.

Malformation (small head size) is also a concern. Findings from animal studies suggest a threshold of about 100 mGy, with the most vulnerable period during embryonic development (2-8 wk after conception). Data collected from those affected by the bombings of Hiroshima and Nagasaki suggest that head size may be slightly reduced as a result of exposure to radiation (< 200 mGy). However, reduction in intelligence did not occur when exposure occurred during the 2nd to 8th weeks after conception. A tendency toward induced intellectual deficit from the 8th to 15th weeks after conception was observed (during this period, the brain undergoes rapid neuron development and migration); however, data are uncertain.

As a general rule, abdominal CT should be avoided in early pregnancy because other diagnostic modalities, such as ultrasonography and diagnostic peritoneal lavage, are acceptable alternatives. CT does, however, allow for better visualization of retroperitoneal and intrauterine injuries. Head and chest CT may be used when indicated because the amount of radiation is much less and because few, if any, alternative diagnostic modalities exist.


Assess fetal viability and for multiple gestations.

Assess the size, gestational age, and position of the fetus.

Ultrasonography can depict free intraperitoneal fluid or hemorrhage in the mother. The focused assessment with sonography for trauma (FAST) examination has become routine in many trauma centers and has been shown to have high sensitivity and accuracy in the hands of emergency clinicians and trauma surgeons.


No reports of adverse effects (but few data) exist.

Ventilation-perfusion (V/Q) scanning

No reports of adverse effects (but few data) exist.

Other Tests

Cardiotocographic monitoring

All pregnant trauma victims of 20-24 weeks of gestational age or greater should be placed on a fetal monitor.

Fetal distress may be the first sign of maternal hemodynamic compromise because the mother will maintain her vital signs by shunting blood away from the relatively low-resistance uterus.

A minimum of 4 hours of monitoring is suggested, even after minor abdominal or flank trauma, to identify patients that might experience placental abruption. This is because clinical signs and symptoms or abruption, such as vaginal bleeding, abdominal pain and tenderness, and uterine tenderness, are often absent.

Monitoring for 24 hours is suggested with major trauma or signs of obstetric decompensation, such as persistent uterine contractions, vaginal bleeding, premature rupture of the membranes, or fetal heart rate tracing that causes concern.

Ultrasonography has less than 50% sensitivity in diagnosing placental abruption because the density of a fresh clot of blood behind the placenta is the same as the placenta itself.


The electrocardiography (ECG) may change as the diaphragm elevates.

It may show a left-axis deviation with flattened T waves and, possibly, a Q wave in leads III and aVF.

Do not mistake these changes for the ischemic or traumatic changes in blunt chest trauma.


Diagnostic peritoneal lavage (DPL)

This study is rarely used nowadays with the advent of ultrasonography. It may be indicated in the pregnant patient where avoidance of radiation exposure through the use of CT is desired and in whom ultrasonography is either unavailable or equivocal. DPL is safe if performed above the umbilicus with an open technique (lower risk of complications such as inadvertent uterine and fetal injury).

Perimortem cesarean delivery

This is performed for two indications: In the case of certain maternal death due to severe head injury or other non-resuscitatable cause, the indication is to save the fetus. In the case of maternal cardiac arrest due to a potentially resuscitatable cause such as a cardiac event or severe blood loss, the indication for the perimortem cesarean delivery is to remove the fetus so as to remove a nonvital organ from the maternal circulation and therefore facilitate the resuscitation.

In either indication, perform this within 4 minutes of cardiac arrest to support neurologic function of the fetus.

The key to rapid delivery is the use of large of incisions.

Perform a midline vertical incision from the xiphoid to the pubis through all layers of the abdominal wall. If the placenta is in an anterior position, cut through it and address the bleeding only after the fetus is delivered.

Perform a midline vertical incision through the upper uterine segment.

Then, remove the neonate, perform suctioning, clamp and cut the cord, and resuscitate the neonate.

Continue resuscitation of the mother.



Prehospital Care

As in any trauma patient, the ABCs of trauma resuscitation must be followed in treating the pregnant patient. The mother should always receive supplemental oxygen. Several additional issues must be considered in treating the trauma patient who is pregnant. Note the following:

  • For patients beyond the 20th to 24th week of gestation, the patient should be tilted 15° to the left by placing rolled towels beneath the spinal board. This is completed to prevent supine hypotension syndrome, which occurs when the gravid uterus compresses the inferior vena cava. Such compression can decrease cardiac output by up to 28%, which then may cause significant hypotension. Alternatively, one person may be designated to manually displace the uterus to the left. If the patient does not require spinal immobilization, then she can be asked to assume the left lateral decubitus position.

  • If warranted, fetal heart tones may be auscultated as part of the initial fetal assessment and to reassure the mother.

  • Military antishock trousers (MAST) are considered a class III intervention (inappropriate, possibly harmful) for gravid patients. If they are used, inflate only the leg compartments.

Emergency Department Care

Patients who have minor trauma and who are at less than 20 weeks' gestation do not require specific intervention or monitoring. All pregnant women beyond 20-24 weeks' gestation who have direct or indirect abdominal trauma should undergo at least 4 hours of cardiotocographic monitoring.

Resuscitation of the more serious trauma patient must focus on the mother because the most common cause of fetal death is maternal shock or death. It is important to remember that the mother will maintain her vital signs at the expense of the fetus. Because plasma volume is increased 50% and the mother is able to shunt blood away from the uterus, maternal shock may not manifest itself until maternal blood loss exceeds 30%. During the initial ABC assessment, the fetus is addressed only during evaluation of circulation.

If the patient is more than 20-24 weeks' pregnant, the patient should be tilted 15° to the left. Alternatively, one person may be designated to manually displace the uterus to the left. If the patient does not require spinal immobilization, then she can be asked to assume the left lateral decubitus position.

A study conducted at a level I trauma center found that implementation of a perinatal emergency response team reduced the mean time to obstetrical evaluation by 30 minutes.[10]

Airway and breathing

All pregnant trauma patients should receive supplemental oxygen because the fetus is extremely sensitive to hypoxia and because the oxygen reserve is significantly diminished in the pregnant patient.

In general, pregnancy does not affect the decision to intubate, although the risk of aspiration is increased (decreased gastric tone, delayed gastric emptying, and cephalad displacement of intra-abdominal organs). The use of medications for rapid sequence intubation in pregnancy is not well studied; however, no absolute contraindications exist.

If a chest tube is placed, enter the chest 1 or 2 interspaces higher than usual, because the diaphragm is elevated during pregnancy.


It is extremely important to maintain adequate maternal blood volume as a first step in fetal resuscitation. A decrease in maternal blood pressure may result in a decrease in uterine blood flow, even without uterine artery vasoconstriction.

Resuscitate the patient with warmed crystalloid administered through large-bore catheters placed for intravenous lines because the relative hypervolemia of pregnancy allows for a 30-35% loss of blood volume before hypotension develops.

Rule out occult sources of bleeding because maternal blood flow is maintained at the expense of fetal blood flow.

If blood is needed on an emergency basis, use Rh-negative blood unless the patient's Rh status is known.

Blood pressure returns to prepregnancy levels as the gestational age approaches 40 weeks.

Fetal assessment should be performed early as part of the maternal secondary survey.

Admission and discharge criteria for pregnant trauma patients

Hospitalization is warranted in pregnant trauma patients with the following:

  • Abnormal obstetric findings, such as vaginal bleeding

  • Abnormal fetal heart rate tracings (eg, variable decelerations)

All serious trauma victims who are beyond 23 weeks EGA require 24 hours of fetal monitoring.

Discharge criteria include no abnormal obstetric findings and normal fetal heart tracings.

Instruct the patient to return in the event of decreased fetal activity, vaginal bleeding, uterine contractions and/or cramping, or spontaneous premature rupture of the membranes.


Transfer the patient to a level I trauma center with obstetric and neonatal intensive care units (NICUs).


The pregnant patient with serious traumatic injury requires a multidisciplinary team, which includes an obstetrician, trauma surgeon, and neonatologist.



Medication Summary

The goal of therapy is to prevent immune response to Rh-negative fetus after trauma. RhoGAM (Rh immunoglobulin G) is administered for this purpose.

Immune serum

Class Summary

Suppresses immune response of nonsensitized Rho(D)–negative mothers who are exposed to Rho(D)–positive blood from the fetus, resulting from a fetomaternal hemorrhage, abdominal trauma, amniocentesis, abortion, full-term delivery, or transfusion accident.

Rho(D) immune globulin (RhoGAM)

Administered if the patient is Rh-negative, unless the father also is Rh-negative. Suppresses the immune response of nonsensitized Rh-negative mothers after delivery of Rh-positive infant. Prevents sensitization to Rho(D) factor. Prevents erythroblastosis fetalis in subsequent pregnancy. When administered near the time of delivery, RhIgG may interfere with Rh typing of the newborn.