Pregnant women comprise a stable proportion of our trauma patients despite declining birth and pregnancy rates in the population, which raises concern that the relative risk of suffering traumatic injury while pregnant may be increasing. Pregnant women are more likely to be admitted to the hospital despite having less severe injuries and less substance use (primarily explained by less alcohol use), which likely reflects a deliberate (and appropriate) abundance of caution in this population. One factor driving admission of pregnant patients is the need for fetal monitoring, particularly in the third trimester. Another factor relates to the reduced number of abdominal CT scans obtained: in the setting of blunt abdominal trauma, serial abdominal exams and laboratory tests may replace initial CT imaging, but requires admission and longer observation. There is a suggestion that clinicians remain reluctant to utilize CT imaging in pregnant women, despite evidence that fetal exposure is comparatively small and guidelines discouraging the withholding of otherwise indicated imaging based on pregnancy.¹¹ This may be one driver of the slightly shorter length of stay in the pregnant cohort (and associated marginally decreased hospital costs).

However, after adjusting for injury severity and other confounders, pregnant women demonstrated higher mortality than their matched nonpregnant controls (see Table 2). This finding corroborates two prior analyses from earlier time periods demonstrating higher mortality,^12,13 in direct contrast to a national analysis suggesting that pregnancy has a protective effect in trauma.⁴ Our analysis reinforces the concern that pregnancy remains a period of vulnerability and can complicate the challenges of appropriate assessment, resuscitation, and rescue after serious injury.

	Pregnant		Not pregnant		p
	n = 140		n = 618
Age (years)	25.5	[21.5, 32]	26	[21, 32]	0.91
ISS	1	[1, 5]	1	[1, 5]	0.12
Penetrating trauma	5	(3.6%)	19	(3.1%)	0.15
Hospital charges	US$27,216	[US$19,612, US$35,999]	US$29,719	[US$23,313, US$42,234]	0.02
Length of stay (days)	1	[1, 2]	0	[1, 2]	0.06

Why may pregnant women be at greater risk? Causal inference is beyond the power of this analysis, but prior studies have demonstrated higher rates of motor vehicle collision and assault (typically by an intimate partner)¹⁴ during pregnancy, with higher ISSs specifically for the abdominal region compared with nonpregnant patients.¹⁵ Substantial morbidity and mortality from abdominal injuries in pregnant patients have been highlighted by prior research.¹⁶

Once injured, pregnant women may face greater physiologic challenges in resuscitation—for instance, caval compression and impaired venous return by a gravid uterus.¹⁷ Recognizing that the presence of the fetus may impair chances of maternal survival, recent efforts have reconceptualized the goals of perimortem cesarean delivery with the concept of “resuscitative hysterotomy” geared toward maternal rescue.¹⁸

Logistical and operational factors undoubtedly play a role as well. The most striking case in our cohort was one in which pregnancy was not recognized during the prehospital phase of care, and a patient with a potentially survivable blunt injury died of hemorrhage (with concomitant fetal demise) with delayed resuscitation efforts that otherwise would have been immediately employed. Because she was initially triaged as a level II trauma and upgraded only after arrival, interventions were performed in the emergency department with suboptimal resources and coordination. In contrast, patients triaged to our highest level bypass the emergency department and go directly to the operating room, with an anesthesiologist and trauma surgeon in the room awaiting their arrival, a practice that has demonstrated improved survival for the most severely injured patients,¹⁹ and may have improved the likelihood of rescue in this case. Had a third-trimester pregnancy been identified in the field, the in-house obstetrician also would have been alerted and would have been present in the operating room on patient arrival. Instead, he was called only after the patient had arrested, which delayed his assistance in the laparotomy and his performance of a perimortem cesarean delivery. Immediate perimortem cesarean delivery improves the probability of both maternal and fetal survival.¹⁸ This case highlights the importance of considering pregnancy in all female patients of reproductive age and utilizing frank questioning as well as objective testing (bHCG, ultrasound) early in their clinical course.

This analysis has a number of limitations inherent to a retrospective, single-institution study. Small cohort size and modest injury severity contributed to limited numbers for analysis. It is important to recognize that our center does not see every trauma patient in the state, and that state-level demographic data used in denominators do not permit absolute population-level estimates, but do permit trend analyses. It is also important to note that trauma during pregnancy may be associated with adverse pregnancy outcomes remote from the trauma admission,^13,20 and that our study design underappreciates these late effects.

Some classification bias may have been present in under-identifying pregnant women, because while universal testing of all WRA was the institutional standard of care, it is likely that compliance with this standard was achieved in fewer than 100% of WRA. This type of bias is unlikely to change the results, as it would tend to skew findings toward the null hypothesis.

This study has limited external validity for centers that see more penetrating trauma or different demographics of their trauma population. Matching was able to adjust for the most striking baseline difference in patient characteristics, but it is possible some residual confounding was present.

Nonetheless, the magnitude of the increase in mortality observed lends credence to the finding that pregnant trauma patients experience higher risk of death.