Fertility treatment increases the risk of preterm birth independent of multiple gestations

To investigate the complex interplay between fertility treatment, multiple gestations, and prematurity. Retrospective cohort study linking the national Center for Disease Control and Prevention infant birth and death data from 2014 to 2018. National database from Center of Disease Control and Prevention. In total, 19,454,155 live-born infants with gestational ages 22–44 weeks, 114,645 infants born using non IVF fertility treatment (NIFT), and 179,960 via assisted reproductive technology (ART). Noninvasive fertility treatment or ART vs. spontaneously conceived pregnancies. The main outcome assessed was prematurity. Formal mediation analysis was conducted to calculate the percentage mediated by multiple gestations. Newborns born using NIFT or ART compared with those with no fertility treatment had a higher incidence of multiple gestation (no fertility treatment = 3.0%; NIFT = 24.7%; ART = 32.7%; P