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 2013 systematic review on this topic noted that the available literature is characterized by severe limitations, including retrospective design, widely variable outcomes, and ascertainment bias.  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.
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.
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.
Falls caused over half of reported injuries during pregnancy; 51.6% and 9.5% of reported injuries were intentionally inflicted.  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.  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. 
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. 
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%).  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. 
Mendez-Figueroa H, Dahlke JD, Vrees RA, Rouse DJ. Trauma in pregnancy: an updated systematic review. Am J Obstet Gynecol. 2013 Jan 17. [Medline].
Tinker SC, Reefhuis J, Dellinger AM, Jamieson DJ. Epidemiology of maternal injuries during pregnancy in a population-based study, 1997-2005. J Womens Health (Larchmt). 2010 Dec. 19(12):2211-8. [Medline].
Lavecchia M, Abenhaim HA. Cardiopulmonary resuscitation of pregnant women in the emergency department. Resuscitation. 2015 Jan 24. [Medline].
Petrone P, Talving P, Browder T, et al. Abdominal injuries in pregnancy: a 155-month study at two level 1 trauma centers. Injury. 2010 Jul 23. [Medline].
Chibber R, Al-Harmi J, Fouda M, El-Saleh E. Motor-vehicle injury in pregnancy and subsequent feto-maternal outcomes: of grave concern. J Matern Fetal Neonatal Med. 2015 Mar. 28(4):399-402. [Medline].
Gazmararian JA, Lazorick S, Spitz AM, Ballard TJ, Saltzman LE, Marks JS. Prevalence of violence against pregnant women. JAMA. 1996 Jun 26. 275(24):1915-20. [Medline].
Berthelot N, Ensink K, Bernazzani O, Normandin L, Luyten P, Fonagy P. Intergenerational transmission of attachment in abused and neglected mothers: the role of trauma-specific reflective functioning. Infant Ment Health J. 2015 Mar-Apr. 36(2):200-12. [Medline].
Mofidi M, Hasani A, Kianmehr N. Determining the accuracy of base deficit in diagnosis of intra-abdominal injury in patients with blunt abdominal trauma. Am J Emerg Med. 2010 Oct. 28(8):933-6. [Medline].
Bochicchio GV, Haan J, Scalea TM. Surgeon-performed focused assessment with sonography for trauma as an early screening tool for pregnancy after trauma. J Trauma. 2002 Jun. 52(6):1125-8. [Medline].
Connolly AM, Katz VL, Bash KL, McMahon MJ, Hansen WF. Trauma and pregnancy. Am J Perinatol. 1997 Jul. 14(6):331-6. [Medline].
Crosby WM, Costiloe JP. Safety of lap-belt restraint for pregnant victims of automobile collisions. N Engl J Med. 1971 Mar 25. 284(12):632-6. [Medline].
Curet MJ, Schermer CR, Demarest GB, Bieneik EJ 3rd, Curet LB. Predictors of outcome in trauma during pregnancy: identification of patients who can be monitored for less than 6 hours. J Trauma. 2000 Jul. 49(1):18-24; discussion 24-5. [Medline].
Dhanraj D, Lambers D. The incidences of positive Kleihauer-Betke test in low-risk pregnancies and maternal trauma patients. Am J Obstet Gynecol. 2004 May. 190(5):1461-3. [Medline].
El-Kady D, Gilbert WM, Anderson J, Danielsen B, Towner D, Smith LH. Trauma during pregnancy: an analysis of maternal and fetal outcomes in a large population. Am J Obstet Gynecol. 2004 Jun. 190(6):1661-8. [Medline].
Esposito TJ. Trauma during pregnancy. Emerg Med Clin North Am. 1994 Feb. 12(1):167-99. [Medline].
Fildes J, Reed L, Jones N, Martin M, Barrett J. Trauma: the leading cause of maternal death. J Trauma. 1992 May. 32(5):643-5. [Medline].
Goldman SM, Wagner LK. Radiologic management of abdominal trauma in pregnancy. AJR Am J Roentgenol. 1996 Apr. 166(4):763-7. [Medline].
Harper M, Parsons L. Maternal deaths due to homicide and other injuries in North Carolina: 1992-1994. Obstet Gynecol. 1997 Dec. 90(6):920-3. [Medline].
Mattox KL, Goetzl L. Trauma in pregnancy. Crit Care Med. 2005 Oct. 33(10 Suppl):S385-9. [Medline].
Muench MV, Baschat AA, Reddy UM, et al. Kleihauer-betke testing is important in all cases of maternal trauma. J Trauma. 2004 Nov. 57(5):1094-8. [Medline].
Pak LL, Reece EA, Chan L. Is adverse pregnancy outcome predictable after blunt abdominal trauma?. Am J Obstet Gynecol. 1998 Nov. 179(5):1140-4. [Medline].
Pearlman MD, Tintinalli JE, Lorenz RP. Blunt trauma during pregnancy. N Engl J Med. 1990 Dec 6. 323(23):1609-13. [Medline].
Pearlman MD, Tintinallli JE, Lorenz RP. A prospective controlled study of outcome after trauma during pregnancy. Am J Obstet Gynecol. 1990 Jun. 162(6):1502-7; discussion 1507-10. [Medline].
Poole GV, Martin JN Jr, Perry KG Jr, Griswold JA, Lambert CJ, Rhodes RS. Trauma in pregnancy: the role of interpersonal violence. Am J Obstet Gynecol. 1996 Jun. 174(6):1873-7; discussion 1877-8. [Medline].
Shah AJ, Kilcline BA. Trauma in pregnancy. Emerg Med Clin North Am. 2003 Aug. 21(3):615-29. [Medline].
Theodorou DA, Velmahos GC, Souter I, et al. Fetal death after trauma in pregnancy. Am Surg. 2000 Sep. 66(9):809-12. [Medline].
Vivian-Taylor J, Roberts CL, Chen JS, Ford JB. Motor vehicle accidents during pregnancy: a population-based study. BJOG. 2012 Mar. 119(4):499-503. [Medline].
Andrew K Chang, MD, MS Vincent P Verdile, MD, Endowed Chair in Emergency Medicine, Professor of Emergency Medicine, Vice Chair of Research and Academic Affairs, Albany Medical College; Associate Professor of Clinical Emergency Medicine, Albert Einstein College of Medicine; Attending Physician, Department of Emergency Medicine, Montefiore Medical Center
Andrew K Chang, MD, MS is a member of the following medical societies: American Academy of Emergency Medicine, American Academy of Neurology, American Academy of Pain Medicine, American College of Emergency Physicians, American Geriatrics Society, American Pain Society, Society for Academic Emergency Medicine
Disclosure: Nothing to disclose.
Francisco Talavera, PharmD, PhD Adjunct Assistant Professor, University of Nebraska Medical Center College of Pharmacy; Editor-in-Chief, Medscape Drug Reference
Disclosure: Received salary from Medscape for employment. for: Medscape.
Eric L Legome, MD Professor and Chair, Department of Emergency Medicine, Mount Sinai St Lukes and Mount Sinai West; Vice Chair of Academic Affairs, Department of Emergency Medicine, Icahn School of Medicine at Mount Sinai
Eric L Legome, MD is a member of the following medical societies: American College of Emergency Physicians, Eastern Association for the Surgery of Trauma, New York American College of Emergency Physicians, Society for Academic Emergency Medicine
Disclosure: Nothing to disclose.
Bruce M Lo, MD, MBA, CPE, RDMS, FACEP, FAAEM, FACHE Medical Director, Department of Emergency Medicine, Sentara Norfolk General Hospital; Professor and Assistant Program Director, Core Academic Faculty, Department of Emergency Medicine, Eastern Virginia Medical School
Bruce M Lo, MD, MBA, CPE, RDMS, FACEP, FAAEM, FACHE is a member of the following medical societies: American Academy of Emergency Medicine, American Association for Physician Leadership, American College of Emergency Physicians, American College of Healthcare Executives, American Institute of Ultrasound in Medicine, Emergency Nurses Association, Medical Society of Virginia, Norfolk Academy of Medicine, Society for Academic Emergency Medicine
Disclosure: Nothing to disclose.
Assaad J Sayah, MD, FACEP Senior Vice President and Chief Medical Officer, Cambridge Health Alliance
Disclosure: Nothing to disclose.
Pamela L Dyne, MD Professor of Clinical Medicine/Emergency Medicine, University of California, Los Angeles, David Geffen School of Medicine; Attending Physician, Department of Emergency Medicine, Olive View-UCLA Medical Center
Disclosure: Nothing to disclose.
Research & References of Pregnancy Trauma|A&C Accounting And Tax Services