Importance: Literature has suggested that trauma among pregnant women is associated with an increased risk of adverse pregnancy outcomes. However, limited research has investigated the association of trauma with adverse pregnancy outcomes by using a national data set. Objective: To investigate the association between traumatic injury and adverse pregnancy outcomes. Design, Setting, and Participants: This population-based cohort study of pregnant women in Taiwan linked 3 data sets, the Taiwan Birth Registry, Household Registration Information, and National Health Insurance Research Database, from January 1, 2004, through December 31, 2014. Data, including the characteristics of pregnant women and infants, were extracted from the Taiwan Birth Registry data set; to obtain trauma data, this data set and the Household Registration Information data set were collectively linked to National Health Insurance Research Database data. The combined data set was analyzed from January to July 2019. Adverse pregnancy outcomes and premature delivery were defined using International Classification of Diseases, Ninth Revision, Clinical Modification codes. Exposures: The primary exposures of this study were 2 clinical variables related to injury during pregnancy: medical treatment in the emergency department (yes or no) and hospitalization (yes or no). Main Outcomes and Measures: The main outcome variable was adverse pregnancy outcomes, and the secondary outcome variable was premature delivery. Multivariate logistic regression models were used to investigate the association of injuries with adverse pregnancy outcomes after controlling for demographic characteristics and other pregnancy-related variables. Results: A total of 2973831 pregnant women (2475805 [83.3%] aged 20-34 years) were enrolled between 2004 and 2014, of whom 59681 (2.0%) sought medical treatments due to injuries. Results of multivariate logistic regression models showed that women receiving emergency treatments more than once were 1.08 times as likely (adjusted odds ratio, 1.08; 95% CI, 1.05-1.10) to have adverse pregnancy outcomes than women who received no emergency treatment. Women with injury-related hospitalization were 1.53 times more likely (adjusted odds ratio, 1.53; 95% CI, 1.41-1.65) to have adverse pregnancy outcomes than women who did not sustain injuries. Furthermore, recurrent injuries were associated with a 572% increase in odds of premature delivery (adjusted odds ratio, 6.72; 95% CI, 2.86-15.80). Conclusions and Relevance: In this study, trauma among pregnant women was associated with an increased risk of adverse pregnancy outcomes, as were hospitalization and emergency department visits due to injury..