Preterm Birth and Small Size for Gestational Age in Singleton, In Vitro Fertilization Births Using Donor Oocytes

We used 2006-2015 US National Assisted Reproductive Technology Surveillance System data to compare preterm birth and fetal growth for liveborn singletons (24-42 weeks' gestation) following in vitro fertilization with donor versus autologous oocytes. Using binary and multinomial logistic regression, we computed adjusted odds ratios and 95% confidence intervals for associations between use of donor oocytes and preterm delivery, being small for gestational age (SGA), and being large for gestational age (LGA), stratified by fresh and thawed embryo status and accounting for maternal characteristics and year of birth. There were 204,855 singleton births from fresh embryo transfers and 106,077 from thawed embryo transfers. Among fresh embryo transfers, donor oocyte births had higher odds of being preterm (adjusted odd ratio (aOR) = 1.32, 95% confidence interval (CI): 1.27, 1.38) or LGA (aOR = 1.27, 95% CI: 1.21, 1.33) but lower odds of being SGA (aOR = 0.81, 95% CI: 0.77, 0.85). Among thawed embryo transfers, donor oocyte births had higher odds of being preterm (aOR = 1.57, 95% CI: 1.48, 1.65) or SGA (aOR = 1.22, 95% CI: 1.14, 1.31) but lower odds of being LGA (aOR = 0.87, 95% CI: 0.82, 0.92). Use of donor oocytes was associated with increased odds of preterm delivery irrespective of embryo status; odds of being SGA were increased for donor versus autologous oocyte births among thawed embryo transfers only.