Perinatal outcomes after fresh versus vitrified-warmed blastocyst transfer: retrospective analysis

Objective: To investigate the possible effect of controlled ovarian stimulation on the perinatal outcomes of assisted reproductive technology pregnancies, by comparing the outcomes from fresh ET with frozen ET (FET) with blastocysts of similar quality. Design: Retrospective observational study. Setting: Private fertility center. Patient(s): Seven hundred eighty-four fresh transfers and 382 vitrified-warmed double blastocyst transfers. Intervention(s): None. Main Outcome Measure(s): Miscarriage, perinatal mortality, preterm delivery, live birth, live-birth weights, and gestational age of live births. Result(s): FET resulted in higher implantation rates (51.5% vs. 40.6%), higher live-birth rates per transfer (56.8% vs. 44.3%), and lower ectopic pregnancy rates (0.32% vs. 1.80%). FET pregnancies also had higher day 14 beta hCG levels per implantation (148.2 vs. 176.2 IU/L) and higher infant birth weights (singletons Delta 109.4 g, twins Delta 124 g). Female infants benefitted the most in terms of birth weight. Miscarriage, premature delivery, perinatal morbidity, and live birth per pregnancy were all nonsignificantly different between fresh ET and FET. Conclusion(s): Clinically significant differences between the peri-implantation and perinatal outcomes of fresh ET and FET suggest better endometrial receptivity and placentation in FET cycles. (C) 2015 by American Society for Reproductive Medicine.