P-345 Too cool to be late: the discrepancy between the required and obtained number of oocytes in a social fertility preservation program
Authors: Braga D , Setti A , Carrilho E , Guilherme P , Erthal M  C , Iaconelli Junior A , Borges E 
Published: July 2024

Abstract

Study question
What are the outcomes of thawed oocytes from social fertility preservation (SFP) programs by age? Is the number of cryopreserved oocytes sufficient to achieve pregnancy?

Summary answer
The outcomes of thawed oocytes from SFP programs diminish with age, and the number of cryopreserved oocytes is below the desirable quantity for pregnancy achievement.

What is known already
Social fertility preservation empowers women to safeguard their fertility by anticipating age-related decline and diminished efficacy of fertility treatments in older ages. The effectiveness of oocyte vitrification programs, and consequently fertility preservation, depends on the patient’s age. Previous reports on fertility preservation indicate that, typically, a larger number of oocytes are retrieved in patients aged ≤35 when compared to older patients. Although these reports document that oocyte vitrification preserves developmental potential akin to fresh oocytes, uncertainties persist regarding patient awareness of the adequate number of cryopreserved oocytes needed for pregnancy.

Study design, size, duration
This historical cohort study, conducted at a university-affiliated IVF center from January 2012 to December 2022, analyzed data from 1,332 vitrified oocyte ICSI cycles involving 1,000 SFP program participants. Fertility preservation patients and oocyte thawing cycles (n = 132) were categorized by age as follows: &lt;30 years (n = 55 and 24), 30-35 years (n = 250 and 33), 36-40 years (n = 480 and n = 42), and &gt;40 years (n = 215 and 33) for preservation and thawing, respectively.

Participants/materials, setting, methods
Laboratory and clinical outcomes were compared among the groups. In a subsequent analysis, data from PGT cycles conducted in our laboratory (n = 480) from January to December 2022 were utilized to determine blastulation and euploidy rates within vitrified oocytes. This data, combined with literature findings, was employed to estimate the average number of oocytes required for a patient to reach a 95% cumulative probability of pregnancy. These estimates were then compared with our database findings.

Main results and the role of chance
There were 1,332 cycles of SFP involving 1,000 patients. Among them, 121 (12.2%) returned for oocyte thawing and underwent 132 ICSI cycles. A significant difference in the survival rate was observed among thawed oocytes from patients under 30 compared to those over 40 years-old (&lt;30: 90.7 ± 33, 30-35: 81.4 ± 40.4, 36-40: 83.4 ± 35.5, and &gt;40: 72.3 ± 34, p = 0.047). Additionally, a significantly higher pregnancy rate was observed in the 30–35 age group when compared to those in the group aged &gt;40 years-old (&lt; 30: 50.0 ± 17.7, 30-35: 56.0 ± 85.0, 36-40: 46.3 ± 69.0, and &gt;40: 21.4 ± 93.0, p = 0.048). However, there was no significant difference when comparing fertilization, blastulation, and implantation rates. In the general group, an appropriate number of oocytes to be cryopreserved to achieve a pregnancy chance of 95% would be 17. For patients aging &lt; 30, 30-35, 36-40, and &gt; 40, that would be 7.47, 10.7, 22.5, and 42.8, respectively. Overall, 92 out of 1,000 patients (9.2%) obtained an adequate number of oocytes. When the group was stratified by age, it was observed that 54.5%, 27.2%, 2.5%, and 0% of the patients obtained an adequate number of oocytes to achieve pregnancy.

Limitations, reasons for caution
The retrospective nature of the study and the small patient cohort included in the analysis, when divided by age, may pose limitations. However, the low number of patients returning to utilize their oocytes in SFP is a consistent limitation across all studies.

Wider implications of the findings
These findings underscore the importance of appropriate counseling and encouragement for patients undergoing SFP earlier, ensuring a larger number of oocytes are cryopreserved. This aligns with SFP’s primary objective: enhancing women’s reproductive autonomy by enabling the postponement of childbearing and preserving the biological relationship with future offspring.

Trial registration number
N/A