Objective This study was undertaken to determine the occurrence rates , outcome s, risk factors, and timing of obstetric delivery for trauma sustained during pr egnancy. Study design This is a retrospective cohort study of women hospitalized for trauma in California (1991-1999). International Classification of Disease, ninth revision, Clinical Modification codes, and external causation codes for i njury were identified. Maternal and fetal/neonatal outcomes were analyzed for wo men delivering at the trauma hospitalization (group 1), and women sustaining tra uma prenatally (group 2), compared with nontrauma controls. Injury severity scor es and injury types were used to stratify risk in relation to outcome. Statistic al comparisons are expressed as odds ratios (ORs) with 95%CIs. Results A total of 10,316 deliveries fulfilling study criteria were identified in 4,833,286 tota l deliveries. Fractures, dislocations, sprains, and strains were the most common type of injury. Group 1 was associated with the worst outcomes: maternal death OR 69 (95%CI 42-115), fetal death OR 4.7 (95%CI 3.4-6.4), uterine rupture OR 43 (95%CI 19-97), and placental abruption OR 9.2 (95%CI 7.8-11). Group 2 al so resulted in increased risks at delivery: placental abruption OR 1.6 (95%CI 1 .3-1.9), preterm labor OR 2.7 (95%CI 2.5-2.9), maternal death OR 4.4 (95%CI 1.4-14). As injury severity scores increased, outcomes worsened, yet were stati stically nonpredictive. The type of injury most commonly leading to maternal dea th was internal injury. The risk of fetal, neonatal, and infant death was strong ly influenced by gestational age at the time of delivery. Conclusion Women deliv ering at the trauma hospitalization (group 1) had the worst outcomes, regardless of the severity of the injury. Group 2 women (prenatal injury) had an increased risk of adverse outcomes at delivery, and therefore should be monitored closely during the subsequent course of the pregnancy. This study highlights the need t o optimize education in trauma prevention during pregnancy. Objective This study was undertaken to determine the occurrence rates, outcome s, risk factors, and timing of obstetric delivery for trauma sustained during pr egnancy. Study design This is a retrospective cohort study of women hospitalized for trauma in California (1991-1999). International Classification of Disease, ninth revision, Clinical Modification codes, and external causation codes for i njury were identified. Maternal and fetal / neonatal outcomes were analyzed for wo men delivering at the trauma hospitalization (group 1), and women sustaining trauma prenatally ( group 2), compared with nontrauma controls. Injury severity scor es and injury types were used to stratify risk in relation to outcome. Statistic al comparisons are expressed as odds ratios (ORs) with 95% CIs. Results A total of 10,316 deliveries fulfilled study Criteria were identified in 4,833,286 tota l deliveries. Fractures, dislocations, sprains, and strains were the most common type of injury. Group 1 was associ ated with the worst outcomes: maternal death OR 69 (95% CI 42-115), fetal death OR 4.7 (95% CI 3.4-6.4), uterine rupture OR 43 (95% CI 19-97), and placental abruption OR 9.2 (95% CI 7.8-11). Group 2 al so resulted in increased risks at delivery: placental abruption OR 1.6 (95% CI 1.3-1.9), preterm labor OR 2.7 (95% CI 2.5-2.9), maternal death The type of injury most commonly leading to maternal dea th was internal injury. The risk of fetal, neonatal, and infant, OR 4.4 (95% CI 1.4-14). As injury severity scores increased, outcomes worsened, yet were stati stically nonpredictive. Death was strong ly influenced by gestational age at the time of delivery. Conclusion Women deliv ering at the trauma hospitalization (group 1) had the worst outcomes, regardless of the severity of the injury. Group 2 women (prenatal injury) had an increased risk of adverse outcomes at delivery, and therefore should be be monitored closely during the subsequent course of the pregnancy. This study highlights the need tooptimize education in trauma prevention during pregnancy.