The number of autologous, vitrified mature oocytes needed to obtain three euploid blastocysts increases with age.

OBJECTIVE

To determine the number of mature oocytes required to make at least three euploid blastocysts.

DESIGN

Retrospective cohort study.

SUBJECTS: All patients at a multicenter assisted reproductive technology practice that warmed vitrified autologous oocytes for in vitro fertilization from 2011 to October 2023.

EXPOSURE: Warming oocytes.

MAIN OUTCOME MEASURES: Number of mature (metaphase II [MII]) oocytes to achieve at least three euploid blastocysts.

RESULTS

A total of 1,041 thaw cycles from 986 patients were analyzed. Patients were stratified by age at vitrification. Measures of ovarian reserve decreased with advancing age, as expected. The number of mature oocytes (MII) banked and euploid blastocysts available decreased as age at vitrification increased. Patients aged 35-40 years used preimplantation genetic testing more than those older than 40 years or younger than 35 years. To optimize the chance of a potential live birth by banking at least three euploid blastocysts, patients aged <35 years at vitrification needed a mean of 15 MII oocytes. This number doubled in patients aged ≥38 years and tripled for patients aged >40 years. We also analyzed potential live birth per number of MII oocytes banked, which also increased with age, with 0.13 expected live births per thawed MII oocyte at the age of <35 years and 0.04 expected live births if older than 40 years at time of oocyte vitrification. Age at vitrification was more influential than indication for vitrification for expected outcome of live birth.

CONCLUSION

From previously published literature, three euploid blastocysts provided a 93% chance of a child. From our analysis, patients required a mean of 15 mature oocytes to yield at least three euploid blastocysts if they were aged <35 years at time of vitrification. The required number of MII oocytes doubled in patients aged ≥38 years and tripled in those aged ≥40 years, to achieve the same goal. Given our results, we should encourage egg freeze patients to cryopreserve before the age of 38 years. We should also counsel patients that multiple vitrification cycles will likely be required to achieve a high probability of live birth from future oocyte thaws for women aged ≥38 years.