P-215 Comparison of embryo utilisation and live birth rate between fresh and frozen donor oocytes, with assessment of the impact of paternal age on these parameters
Authors: Wong S , Mascarenhas M 
Published: June 2023

Abstract

Study question
Does paternal age differentially affect the embryo utilisation and live birth rate of fresh and frozen donor oocytes?

Summary answer
The impact of paternal age on embryo utilisation and live birth for frozen donor oocytes is no different from fresh donor oocytes.

What is known already
Frozen donor oocytes are increasingly offered as an alternative to fresh oocytes as it is deemed a more accessible option for patients. There is conflicting data on the impact of paternal age on donor oocyte success rates, with some studies suggesting a declining live birth rate with advancing paternal age and others indicating no difference. However, the current literature appears primarily based on fresh donor oocytes. There is no available information on whether paternal age impacts frozen oocytes (and, if so, whether it differs from the impact on fresh donor oocytes).

Study design, size, duration
This retrospective cohort study analysed 169 616 ART (assisted reproductive technique) cycles from the Human Fertilisation Embryology Authority (HFEA) anonymised database from 2017 to 2018. To reduce bias resulting from age-related oocyte quality and intracytoplasmic sperm injection (ICSI) in frozen oocytes, only fresh and frozen donor oocytes with ICSI were analysed to assess whether paternal age plays a role. Frozen embryo transfer cycles were not included.

Participants/materials, setting, methods
We included 2287 ICSI oocyte donation cycles from the anonymised HFEA database, of which 1551 utilised fresh oocytes and 736 utilised frozen oocytes. Only two years’ worth of data was analysed, as the technology behind oocyte freezing is evolving rapidly with concomitant improvement in success rates. The paternal age group is divided into &gt;40 years old, and &lt;40 years old for analysis to assess for differences.

Main results and the role of chance
Predictably, about 65% of our oocyte recipients in this cohort were more than 40 years of age at the time of treatment. 55% of oocyte donors were under 30 years, and about 64% of the male partners were over 40 years. Paternal age has not been shown to influence the outcome with either fresh or frozen oocytes. When restricting to cycles with paternal age &lt;40 years, the fertilisation rate was higher with fresh oocytes (13.3% with over ten embryos), as compared to 3.0% with frozen oocyte (P &lt; 0.001). In the &gt;40 years paternal age group, the fertilisation rate was also higher using the fresh oocytes, with 13.8% of the group having more than ten embryos formed as compared to 3.2% in the frozen group (P &lt; 0.001). More embryos were also suitable for storing in the &gt;40 years old paternal age group, with 7% of the fresh cohort having more than five embryos suitable for freezing versus 3.6% in the frozen group (P = 0.005). No significant difference was noted in the clinical pregnancy and live birth rate.

Limitations, reasons for caution
Variations in laboratory protocols (such as vitrification methods) between different clinics might lead to the non-uniformity of the dataset, reducing its reliability. Data on cumulative live birth rate was unavailable, and a further project is planned, which would involve requesting the HFEA for this information from linked cycles.

Wider implications of the findings
With the increasing trend towards using frozen donor oocyte banks in the United Kingdom, understanding the implications would allow better patient counselling.

Trial registration number
not applicable