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

Fertil Steril. 2018 Oct;110(5):880-887. doi: 10.1016/j.fertnstert.2018.05.024. Epub 2018 Aug 21.


Objective: To assess in vitro 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).

Design: Retrospective cohort study.

Setting: None.

Patient(s): Registry data on 82,935 patient cycles from the Society for Assisted Reproductive Technology (SART).

Intervention(s): 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.

Main outcome measure(s): Clinical pregnancy rate (CPR) and live-birth rate (LBR).

Results: 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%).

Conclusion(s): 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.

Keywords: FET; IVF; fresh embryo transfer; frozen embryo transfer; in vitro fertilization.

MeSH terms

  • Adult
  • Cohort Studies
  • Cryopreservation / methods
  • Cryopreservation / trends*
  • Female
  • Fertilization in Vitro / methods
  • Fertilization in Vitro / standards
  • Fertilization in Vitro / trends*
  • Humans
  • Pregnancy
  • Pregnancy Outcome* / epidemiology
  • Pregnancy Rate / trends*
  • Registries*
  • Retrospective Studies
  • Societies, Medical / trends*