Association between unintentional injury during pregnancy and excess risk of preterm birth and its neonatal sequelae.

The sequelae of preterm births may differ, depending on whether birth follows an acute event or a chronic condition. In a population-based cohort study of 2,711,645 Canadian hospital deliveries from 2003 to 2012, 3,059 women experienced unintentional injury during pregnancy. We assessed the impact of the acute event on pregnancy outcome and on neonatal complications, such as nontraumatic intracranial hemorrhage, respiratory distress syndrome, intubation, and death. We adjusted for maternal age, parity, pregnancy conditions, and (for neonates) gestational age in logistic regression analyses. Injury was significantly associated with fetal mortality and early preterm delivery. For preterm infants born to injured women during the hospitalization for injury versus those born to noninjured women, the adjusted odds ratios were 2.25 (95% confidence interval (CI): 1.23, 4.17) for neonatal death, 2.44 (95% CI: 1.76, 3.37) for respiratory distress, 2.20 (95% CI: 1.26, 3.84) for nontraumatic intracranial hemorrhage, and 2.17 (95% CI: 1.60, 2.96) for intubation, despite more favorable fetal growth in those born to noninjured women (adjusted birth-weight-for-gestational-age z score: 0.154 vs. 0.024, P = 0.041; small-for-gestational-age rate: 4.5% vs. 9.5%, P = 0.001). Our findings suggest that adaptation to the suboptimal intrauterine environment underlying chronic causes of preterm birth may protect preterm infants from adverse sequelae.