P-371 It’s worth the freeze: outcomes from thawing electively cryopreserved oocytes are comparable in patients with reduced vs normal ovarian reserve at the time of cryopreservation
Authors: Resetkova N , Hillis N , Duvall D , Sakkas D 
Published: July 2024

Abstract

Study question
For patients coming back to use oocytes derived from elective cryopreservation, does their initial ovarian reserve predict thaw survival, embryos’ developmental milestones and pregnancy success?

Summary answer
Thaw survival, fertilization rate, embryo development and pregnancy success rates do not vary significantly according to AMH level at initial cryopreservation.

What is known already
Increasing numbers of patients are electing to cryopreserve oocytes for future use. AMH (Anti Mullerian Hormone) is an ovarian reserve marker often assessed prior to initiation of treatment that predicts response to fertility treatment and the resulting oocyte yield. However, it is not known whether oocytes derived from a patient with compromised ovarian reserve (perhaps over multiple treatment cycles) will fare as well as that of a patient with normal ovarian reserve and a higher per cycle oocyte yield. Our study seeks to shed light on whether a lower initial AMH level negatively impacts the prognosis of the thawed oocytes.

Study design, size, duration
We included in our retrospective study all oocyte thaw cycles resulting from electively cryopreserved oocytes since 1996 at a single academically affiliated fertility center. 325 patients completed a total of 510 thaw cycles. 315 cycles were excluded from analysis for no AMH information. 6376 oocyte cryopreservation cycles were performed over that timeframe. The primary outcomes were laboratory statistics including oocyte survival, fertilization and embryo blastulation rates, while the secondary outcome was cumulative live birth rates.

Participants/materials, setting, methods
AMH categories of &lt; 1, 1-2 and &gt; 2 were selected to stratify reduced, low-normal, and normal ovarian reserves, respectively. 70.7% inseminated oocytes with partner sperm while the remaining 29.3% used donor sperm.
Mean age at time of oocyte cryopreservation was 36.5 (range 27.5 to 46.2) while mean age at time of oocyte thaw was 39.2 (range 27.7 to 47.5). The statistical analysis was performed using ANOVA for mean comparisons and chi-squared for pregnancy data.

Main results and the role of chance
Average oocyte yield per cryopreservation cycle was significantly different across AMH groups (7.7 oocytes in AMH &lt; 1, 10.5 oocytes in AMH 1-2, and 17.2 oocytes in AMH &gt; 2, p &lt; 0.01). The number of treatment cycles completed was highest in patients with AMH &lt; 1 at 1.26 cycles.
Oocyte survival (mean 89.0%), fertilization rate (mean 75.3%), and blastocyst conversion rate (mean 62.4%) did not vary significantly across AMH groups.
Time to oocyte use was not significantly impacted by AMH at the time of initial testing. Those with reduced AMH &lt; 1 came back earlier to utilize the oocytes (787 days), vs 1141 days for patients with AMH 1-2 and 1021 days for patients with AMH &gt; 2. However, this difference was not statistically significant, p = 0.4.
The rate of PGT-A euploid embryos did not vary between groups (38.8% in AMH &lt; 1, 45.3% in AMH 1-2, 53.0% in AMH &gt; 2, p = 0.07). Clinical pregnancy, miscarriage rate, and live birth rate in the first transfer cycle was not impacted by AMH. Total cumulative live birth rate was not correlated with AMH (31.6% in AMH &lt; 1, 44.4% in AMH 1-2, 47.8% in AMH &gt; 2, p = 0.48).

Limitations, reasons for caution
This data was collected at a single fertility center and thus has limited generalizability. 8.0% of patients came back to utilize their oocytes, which varies widely across the published literature. 60.6% of patients did not have AMH assessed as part of their pre-treatment testing and were excluded from analysis.

Wider implications of the findings
Although reduced ovarian reserve impacts oocyte yield, many studies find no impact on resulting oocyte quality, embryo development and pregnancy success rates. Those with compromised AMH have comparable oocyte thaw outcomes to those with normal ovarian reserve, though more oocyte cryopreservation cycles may be needed to achieve a successful outcome.

Trial registration number
N/A