Fertil Steril

ObjectiveTo investigate the risk of preterm birth among liveborn singletons to primiparas who conceived with assisted reproductive technology (ART) using four mutually exclusive categories of infertility (female infertility only, male infertility only, female and male infertility, and unexplained infertility) and to examine preterm birth risk along the gestational age continuum.DesignRetrospective cohort study.SettingNot applicable.Patient(s)Singletons born to primiparas who conceived with or without ART.Intervention(s)None.Main Outcome Measure(s)Preterm (<37 weeks\u2019 gestation) and preterm/early term birth