BACKGROUND: Approximately 8% of all pregnant women experience a traumatic injury during pregnancy. There has been no evaluation of a state trauma system's effect on birth outcomes. This study examined the association of treatment in a designated trauma hospital vs a nontrauma hospital on maternal and neonatal outcomes among injured pregnant patients in Washington State. STUDY DESIGN: We conducted a population-based retrospective cohort study (1995 to 2012). The Washington State Birth Events Records Database and the Comprehensive Hospital Abstract Recording System were linked to ascertain all hospitalized injured pregnant patients. The cohort was dichotomized by exposure to trauma vs nontrauma hospitals. We analyzed the association between trauma hospital designation and risk of adverse birth outcomes using logistic regression to estimate odds ratios and 95% CI, adjusting for Injury Severity Score and other confounders. RESULTS: We ascertained 3,429 injured pregnant women. Patients treated in trauma hospitals had an adjusted odds ratio (aOR) of 0.60 (95% CI, 0.50-0.73) for preterm labor, aOR = 0.74 (95% CI, 0.57-0.96) for gestational age <37 weeks, aOR = 0.72 (95% CI, 0.54-0.97) for birth weight <2,500 g, and aOR = 0.54 (95% CI, 0.39-0.76) for meconium at delivery. No statistically significant associations were found for maternal death (aOR = 2.57; 95% CI, 0.32-20.38), fetal death (aOR = 1.60; 95% CI, 0.35-7.35), or neonatal death (aOR = 1.50; 95% CI, 0.50-4.49). CONCLUSIONS: Treatment of injured pregnant women at designated trauma hospitals was associated with several improved birth outcomes. Trauma hospital treatment, with a greater focus on maternal resuscitation and monitoring, might explain these findings.