Freezing of all embryos in in vitro fertilization is beneficial in high responders, but not intermediate and low responders: an analysis of 82,935 cycles from the Society for Assisted Reproductive Technology registry

Abstract

To assess invitro fertilization (IVF) and pregnancy outcomes in patients having their first frozen embryo transfer (FET) after a freeze-all cycle versus similar patients having their first fresh embryo transfer (ET). Retrospective cohort study. None. Registry data on 82,935 patient cycles from the Society for Assisted Reproductive Technology (SART). All first fresh autologous IVF cycles were analyzed and compared to first FET cycles after a freeze-all first IVF stimulation. The cycles were subdivided into cohorts based upon the number of oocytes retrieved (OR): 1-5 (low), 6-14 (intermediate), and 15+ (high responders). Univariate analyses were performed on cycle characteristics, and multivariable regression analyses were performed on outcome data. Clinical pregnancy rate (CPR) and live-birth rate (LBR). Of the 82,935 cycles analyzed, 69,102 patients had their first fresh transfer, and 13,833 had a first FET. High responders were found to have a higher CPR and LBR in the FET cycles compared with the fresh ET cycles (61.5 vs. 57.4%; 52.0 vs. 48.9%). In intermediate responders, both CPR and LBR were higher after fresh ET compared with FET (49.6% vs. 44.2%; 41.2 vs. 35.3%). Similarly, in low responders, CPR and LBR were higher after fresh compared with FET (33.2% vs. 15.9%; 25.9% vs. 11.5%). A freeze-all strategy is beneficial in high responders but not in intermediate or low responders, thus refuting the idea that freeze-all cycles are preferable for all patients.