A decade of elective egg freezing in Brazil: reproductive outcomes of women using stored oocytes

What are the reproductive outcomes of women who returned to a Brazilian fertility clinic to achieve motherhood after elective oocyte cryopreservation (EOC)?

Retrospective single-centre study (n = 2073 women; n = 2431 EOC cycles) between January 2013 and December 2022. Women freezing oocytes for medical indications or infertility treatment were excluded.

Mean age at freezing was 36.5 ± 2.8 years. The annual number of EOC cycles increased nearly 500% from 2013 to 2022. Of 1755 women with cryopreserved oocytes, 134 (7.6%) returned to the same clinic for oocyte warming after a mean interval of 4.1 ± 2.2 years; from this cohort, 69% achieved embryo transfer and 47.3% of those achieved a live birth. Older age at freezing was associated with lower odds of reaching embryo transfer (adjusted OR [aOR] 0.86, 95% CI 0.74 to 0.99, P = 0.037), whereas a higher cumulative number of vitrified mature oocytes increased those odds (aOR 1.11, 95% CI 1.03 to 1.20, P = 0.004). The number of oocytes warmed, post-warming survival, fertilization and blastocyst rate were independently associated with embryo transfer; no variable independently predicted live birth. Kaplan-Meier analysis showed cumulative utilization of 4.02% at 3 years and 9.37% at 5 years after freezing. Utilization differed according to cumulative number of vitrified mature oocytes, but not age at freezing. Among women who warmed oocytes, 27% pursued single motherhood.

As elective oocyte cryopreservation increases, a greater number of women may return for future use. Counselling should emphasize freezing at younger ages, achieving an adequate number of vitrified mature oocytes, and the limitations of assisted reproductive technology at advanced maternal age.