Effect of maternal height and weight on risk for preterm singleton and twin births resulting from IVF in the United States, 2008–2010

Objective To analyze the effects of preconception maternal height and weight on the risk of preterm singleton and twin births resulting from in vitro fertilization (IVF). Study Design We performed a retrospective cohort analysis of the incidence of very early preterm birth (VEPTB), early preterm birth (EPTB), and preterm birth (PTB), before 28, 32, and 37 completed weeks, respectively, in 60,232 singleton and 24,111 twin live births using 2008-2010 live birth outcome data from the Society for Reproductive Technology Clinic Outcome Reporting System. Result Maternal obesity is associated with significantly increased risk of VEPTB, EPTB, and PTB in pregnancies conceived by IVF. For morbidly obese women (body mass index ≥35) with singletons, rates of VEPTB, EPTB, and PTB were 1.7%, 3.6%, and 16.4%, with adjusted risk ratios (aRRs) and 95% confidence levels (CIs) of 2.6 (1.8–3.6), 2.2 (1.8–2.6), and 1.5 (1.4–1.7) using corresponding rates for normal body mass index (95% CI, 18.6–24.9) as referent. For morbidly obese women with twins, rate of VEPTB and EPTB were 6.5% and 12.5%, with aRRs and 95% CIs of 2.4 (1.8–3.0) and 1.5 (1.3–1.8). For singletons, the rate of PTB for short stature women (