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; <28 weeks), very preterm (VPTB; <32 weeks), and preterm birth (<37 weeks) births. Result(s): In both singleton and twin births, increased maternal height was associated with a decreased risk of preterm birth. Maternal overweight and obesity were associated with significantly increased risk of VEPTB and VPTB in twin pregnancies. For very obese women (BMI > 35 kg/m2) twins were associated with a threefold increased risk of VEPTB (6.1% vs. 2.0%) and a twofold increased risk of VPTB (11.5% vs. 5.9%) compared with women of normal weight (BMI 18.4–24.9 kg/m2). Conclusion(s): Obesity and short stature significantly increase the risk of VEPTB and VPTB in twins conceived by IVF. [ABSTRACT FROM AUTHOR]