Freezing first: insights from 8 years of planned oocyte cryopreservation at an "egg freezing clinic".

OBJECTIVE

To assess the outcomes of oocyte warming (OW) and embryo transfer in individuals who underwent planned oocyte cryopreservation (OC).

DESIGN

Retrospective cohort study.

SUBJECTS: This study includes all planned OC cycles performed at Extend Fertility before December 31, 2023, and subsequent OW cycles performed before August 2024.

EXPOSURE: Age at the time of OC and number of metaphase (M)II oocytes warmed.

MAIN OUTCOME MEASURES: The primary outcome was cumulative ongoing pregnancy/live birth (OP/LB) rate per OW cycle, stratified by age and number of MII oocytes warmed. Secondary outcomes included OW survival and fertilization rates and the number of euploid embryos per MII oocyte, categorized by age at the time of OC.

RESULTS

Between 2016 and 2023, 4,659 OC cycles were completed for 3,138 patients, with the mean OC start age decreasing from 36.9 ± 2.8 years at the onset to 35.0 ± 3.5 years in the final year of the study. The mean length of time between OC and first OW was 3.4 ± 1.9 years. The mean age at first OW was 39.9 ± 3.5 years, with a median (interquartile range) of 40 (39, 42) years. Among patients who had completed at least one OC cycle before 2020 (n = 2,163), allowing for a minimum follow-up period of 4 years, 10.4% (n = 226) returned for OW. Across 271 OW cycles, the mean number of MII oocytes warmed was 15, with survival and fertilization rates of 90.7% and 77.2%, respectively. Among patients who underwent OC at ≤40 years of age, warming a higher number of MII oocytes was associated with increased euploid embryo yield. The cumulative ongoing pregnancy/live birth rate (OP/LB) rate for the cohort was 70.3%, ranging from 58.3% for 1-9 MII oocytes warmed to 81.8% for >20 MII oocytes warmed.

CONCLUSION

Driven by increased awareness and access, patients are undergoing planned OC at younger ages. This study demonstrates high success rates achieved at an "egg freezing clinic", especially among patients who pursue OC at younger ages. It also establishes a framework to estimate the number of euploid embryos from MII oocytes, as well as the likelihood of live birth, stratified by age at OC.