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Oocytes and embryos are exposed to unnecessary risk during routine fertility cryopreservation and storage


We felt compelled to delve deeper into the risks associated with fertility cryostorage following a Quality Improvement project we completed in the Hewitt Fertility Centres in 2019 focusing on embryo vitrification and warming techniques in the laboratory. As with other established fertility services we were focusing on continuous improvement; trying to make those marginal gains to maybe increase embryo survival by 1-2% or improve our monitoring of the warmed embryo to ensure chance of success is optimised yet embryos are not warmed unnecessarily.

Following on from implementation of the QI plan, in 2020 we performed a Failure Mode and Effect Analysis (FMEA) where the potential risk of each step of vitrification, cryostorage and subsequent warming was scored, and consideration given to how we could mitigate against those identified risks scored with a high Risk Priority Number (RPN). It was the element of cryostorage that surprised us the most.

Fertility cryostorage has not evolved for over 40 years. The Hewitt Fertility Centres are not unusual in their method of cryostorage, and although our scientists are extremely highly-skilled in their cryo-sample handling, adverse handling events do occur. Once we started to consider the number of times our scientific team need to access samples in our cryostore, we knew we had to share this data with other clinics. Although absolute risk is hard to quantify, the number of unnecessary handling events that will significantly increase the risk of an adverse handling event cannot be ignored. In fertility it is now time to focus our attention on our cryostorage systems and prepare for the advent of extended storage for non-medical reasons.

Fertility 2022 Presentation Abstract:

A Failure Mode and Effects Analysis (FMEA) of routine cryostorage processes1 identified two failure modes with a severe RPN >70 (Risk Priority Number, a product of likelihood, severity and detection of incidence) related to the removal of samples from the temperature controlled environment due to handling for warming, cryopreservation, removal or audit. With the advent of extended statutory storage periods for up to 55 years for non-medical cryopreservation, the number of samples remaining in cryostorage will grow and lead to an increased number of handling events outside of the temperature controlled environment.

Aim: To evaluate the current incidence of unnecessary risk exposure to cryostored material in a large fertility facility.

Retrospective activity data were reported for 2019, data included cryostorage exposure events for bi-annual egg/embryo storage audit, egg/embryo warming and cryopreservation events, and discarding from storage. A cryostorage exposure event was considered any action where removal of a patients sample also required the unnecessary removal of co-located patients.

Cryopreserved material for 182 patients was audited as part of a 5% sample audit of 3642 patients. The audit was responsible for 1938 cryostorage exposure events; embryo warms 13,838; embryo storage 10,945, and discard from storage 3245. A total of 29,966 patient’s eggs/embryos were exposed to unnecessary risk for audit or during unrelated treatment.

With the impending increase of cryostorage limits from 10 years to 55 years, and the associated growth in cryostorage contents, clinics face an increased risk to stored material when handling samples for bi-annual inventory, and co-located sample freezing, warming, and removal. Efforts need to be made to evaluate suitable alternatives to current cryostorage systems to mitigate this risk.

  1. Gregoire et al., 2020 Failure Modes and Effects Analysis of current IVF cryostorage processes in a large HFEA licensed clinic. ESHRE 2020