Effect of maternal height and weight on risk of preterm birth in singleton and twin births resulting from in vitro fertilization: a retrospective cohort study using the Society for Assisted Reproductive Technology Clinic Outcome Reporting System

Objective To examine the effect of height, weight, and body mass index (BMI) on the risk of preterm birth of singleton and twin pregnancies conceived by vitro fertilization (IVF). Design Retrospective cohort study using 2006–2008 data from the Society for Reproductive Technology Clinic Outcome Reporting System (SART CORS). Setting SART-associated assisted reproductive technology programs. Patient(s) 56,556 singleton and 23,804 twin live births resulting from fresh nondonor IVF cycles. Intervention(s) None. Main Outcome Measure(s) Rates of very early preterm (VEPTB;