Invited commentary: isolating preterm birth to assess its impact.

Separating the causal impact of early delivery on neonatal health outcomes from the antecedents of early delivery is challenging given the range of pathologies that are typically involved. Isolating preterm births resulting from trauma offers an opportunity to assess the impact of preterm birth independent of the usual causes, and it appears that such births are at substantially increased risk of adverse health outcomes (Am J Epidemiol. 2015;182(9):750-758). Trauma-related preterm births may offer insight into what happens when presumably normally developing fetuses are delivered early. Whereas pathology-related preterm births are preceded by a stressful uterine environment, including multiple contributing factors, and allow for interventions to prepare the newborn for extrauterine life, none of these applies to trauma-related preterm births. However, the trauma itself presumably causes acute problems that lead to the decision to deliver. Generalizing from the findings for trauma-related preterm births suggests that the pathology typically causing preterm birth does not have a strong independent effect and that a longer period leading up to the preterm birth is beneficial whether due to maturation or the opportunity for intervention.