Baby on board: Trauma in pregnancy

Approximately 4 million babies are born annually—11,000 births per day—in the U.S.* An estimated one in 12 pregnancies is complicated by trauma, most commonly motor vehicle crashes, followed by assaults, falls, and intimate partner violence. Of the traumatic injuries occurring during pregnancy, nine out of 10 are classified as “minor,” yet 60–70 percent of fetal loss after trauma results from “minor injuries.”

Physiologic changes in pregnancy

Many physiologic and anatomic changes associated with pregnancy can alter the care of the pregnant patient after a traumatic incident. These changes include a plasma volume increase of 50 percent, resulting in a decrease in hemoglobin/hematocrit and red blood cell count. Platelet counts tend to fall throughout pregnancy but will usually remain within normal limits. Other changes in the coagulation system produce a physiologic hypercoagulable state in preparation for the hemostasis that will need to occur following birth.

Changes in the cardiovascular system begin early in the pregnancy. Systemic vascular resistance decreases with a compensatory 40 percent increase in cardiac output. Maternal heart rate also increases 10–20 beats per minute.

Oxygen demands during pregnancy increase significantly because of heightened metabolic rate and oxygen consumption. To accommodate for this change, minute ventilation rises as a result of taking deeper breaths. This maternal hyperventilation results in an increase in arterial pO2 and decrease in pCO2. Diaphragm elevation in late pregnancy decreases functional residual capacity.

As pregnancy progresses, mechanical changes are produced within the alimentary tract, including the stomach being displaced upwards, leading to increased intragastric pressure. Musculoskeletal changes include exaggerated lordosis of the lower back, forward flexion of the neck, downward movement of the shoulders, joint laxity in the ligaments of the lumbar spine, widening of the symphysis pubis, and increased mobility of the sacroiliac joints.

Findings from NTDB search

To examine the occurrence of injured patients who were pregnant at the time of injury in the National Trauma Data Bank® (NTDB®) research admission year 2016, medical records were searched using the International Classification of Diseases, 10th Revision Clinical Modification codes. Specifically searched were records that contained a diagnosis code of either Z33.1 (pregnant state, incidental), Z3A (weeks of gestation), 09A.211 (injury complicating pregnancy—first trimester), 09A.212 (injury complicating pregnancy—second trimester), 09A.213 (injury complicating pregnancy—third trimester), or 09A.219 (injury complicating pregnancy—unspecified trimester).

A total of 101 records were found, of which 61 contained a discharge status, including 57 patients discharged to home; four died. These patients were female, on average 26.2 years of age, had an average hospital length of stay of 3.5 days, an intensive care unit length of stay of 6.6 days, an average injury severity score of 7.9, and were on the ventilator for an average of 8.3 days. Of the patients tested, 10 percent (four of 39) were over the legal limit for alcohol. For mechanism of injury, see Figure 1.

Figure 1. Mechanism of injury

Figure 1. Mechanism of injury

Fetal monitoring

The most common causes of trauma in the pregnant patient are minor incidents including motor vehicle crashes and blunt abdominal trauma. However, the fetal monitoring recommendations for patients with minor trauma are similar to the monitoring requirements for patients with major trauma. Fetal monitoring should last a minimum of four hours and up to 24 hours after minor trauma and should begin immediately after the primary assessment has been completed. A gravid uterus can compress the inferior vena cava; therefore, it is important to remember to tilt the patient to the left to improve venous return. In cases of extremis, the American Heart Association recommends that perimortem cesarean delivery occur if spontaneous circulation has not returned within four to five minutes post-cardiac arrest in an injured mother.

Throughout the year, we will be highlighting NTDB data through brief monthly reports in the Bulletin. All previous years of the NTDB Annual Report can be found on the ACS website, or as a PDF file. In addition, information is available on the website regarding how to obtain NTDB data for more detailed study. To submit your trauma center’s data, contact Melanie L. Neal, Manager, NTDB, at


Statistical support for this article was provided by Ryan Murphy, Data Analyst, NTDB.

*Centers for Disease Control and Prevention. National Center for Health Statistics. Births and natality. Available at: Accessed September 25, 2017.

Murphy NJ, Quinlan JD. Trauma in pregnancy: Assessment, management, and prevention. Am Fam Physician. 2014;90(10):717-722.

Soma-Pillay P, Nelson-Piercy C, Tolppanen H, Mebazaa A. Physiologic changes in pregnancy. Cardiovasc J Afr. 2016;27(2):89-94.


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