Oocyte vitrification for elective fertility preservation: a SWOT analysis

Clinical outcomes of vitrified-warmed autologous oocyte cycles with 15-year follow-up at a single UK centre: consistent and predictable results

RESEARCH QUESTION

What were the clinical outcomes from 332 autologous vitrified- warmed oocyte cycles derived from 3182 elective autologous oocyte freeze cycles carried out between 2008 and 2022 in a single-centre series?

DESIGN

In this retrospective observational study, outcomes in 299 patients returning to use their frozen oocytes between 2015 and 2023 were analysed.

RESULTS

A total of 3328 elective oocyte vitrification cycles were performed in 2280 patients. The return rate to use oocytes was 14% (299/2171). Mean ages were 37.6 years at storage and 40 at warming. Ninety-three clinical pregnancies and 77 healthy live births were recorded. The live birth rate (LBR) was 24% (39/163) per fresh transfer and 17% (39/227) per embryo transferred. Stratified by age at freezing, the LBR per embryo transferred was 26% (12/47) in participants under 35 years, 20% (24/118) in those 35-39 years and 5% (3/62) in those 40+ years. Frozen embryo transfers (FET) achieved a 30% (24/80) LBR per embryo transfer and a 27% (24/90) LBR per embryo transferred. PGT-A for embryo selection doubled the LBR compared with FET from an untested embryo after one attempt (40% versus 21%). In patients aged over 40 years, the cumulative LBR reached 42% per patient in euploid FET.

CONCLUSION

The proportion of patients who returned to use their stored oocytes and the clinical outcomes were consistent with other recent reports and challenges the prevalent critical narrative regarding elective oocyte freezing for fertility preservation. The results are now comparable to routine IVF. Not everyone who returns to use their oocytes will conceive, but for those choosing to preserve their fertility, oocyte freezing can provide reproducible and reassuring results.

Oocyte retrieval in social fertility preservation: challenging traditional beliefs on gonadotropin dosing and follicular size

OBJECTIVES

To investigate treatment approaches for fertility preservation patients, with a focus on timing of oocyte retrieval, and to determine whether their characteristics differ from those of other IVF patients. Additionally, to evaluate the significance of follicle size on triggering day in the context of fertility preservation.

METHODS

This retrospective cohort study was conducted in a tertiary, university-affiliated medical center. It compared 140 matched patients undergoing social fertility preservation to 140 patients undergoing IVF treatment due to male factor infertility.

RESULTS

Patients undergoing fertility preservation received a higher initial gonadotropin dose and had more oocytes retrieved than the control group. Within the fertility preservation cohort, a negative correlation was observed between the rate of large follicles and the number of retrieved oocytes. While there was no significant association between rate of large follicles and oocyte maturation rate in the entire group, age-stratified analysis revealed a negative relationship. Analysis revealed that although traditional treatment determinants such as follicular size and gonadotropin dosing were considered, peak estradiol levels were consistently identified as significant predictors of treatment outcomes.

CONCLUSIONS

Physicians may modify treatments for fertility preservation, emphasizing a higher gonadotropin dosage to maximize oocyte retrieval. Elevated estradiol levels can serve as a real-time predictive marker for the number of mature oocytes. While treatment strategies can influence outcomes, intrinsic patient factors, particularly baseline ovarian function, remain crucial. These results challenge beliefs regarding the importance of larger follicles and suggest the need for a tailored approach, considering patient age and specific fertility preservation objectives.

Improving vitrification efficiency of human in vitro matured oocytes by the addition of LEA proteins

STUDY QUESTION

Can the addition of late embryogenesis-abundant (LEA) proteins as a cryoprotective agent during the vitrification cryopreservation of in vitro matured oocytes enhance their developmental potential after fertilization?

SUMMARY ANSWER

LEA proteins improve the developmental potential of human in vitro matured oocytes following cryopreservation, mostly by downregulating FOS genes, reducing oxidative stress, and inhibiting the formation of ice crystals.

WHAT IS KNOWN ALREADY

Various factors in the vitrification process, including cryoprotectant toxicity, osmotic stress, and ice crystal formation during rewarming, can cause fatal damage to oocytes, thereby affecting the oocytes developmental potential and subsequent clinical outcomes. Recent studies have shown that LEA proteins possess high hydrophilicity and inherent stress tolerance, and can reduce low-temperature damage, although the molecular mechanism it exerts protective effects is still unclear.

STUDY DESIGN, SIZE, DURATION

Two LEA proteins extracted and purified by us were added to solutions for vitrification-warming of oocytes at concentrations of 10, 100, and 200 µg/mL, to determine the optimal protective concentration for each protein. Individual oocyte samples were collected for transcriptomic analysis, with each group consisting of three sample replicates.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Immature oocytes were collected from patients who were undergoing combined in vitro fertilization (IVF) treatment and who had met the designated inclusion and exclusion criteria. These oocytes underwent in vitro maturation (IVM) culture for experimental research. A fluorescence microscope was used to detect the levels of mitochondrial membrane potential (MMP), reactive oxygen species (ROS), and calcium in the mitochondria of vitrified-warmed human oocytes treated with different concentrations of LEA proteins, and the protective effect of the protein on mitochondrial function was assessed. The levels of intracellular ice recrystallization inhibition (IRI) in human oocytes after vitrification-warming were characterized by the cryomicroscope, to determine the LEA proteins inhibitory effect on recrystallization. By analyzing transcriptome sequencing data to investigate the potential mechanism through which LEA proteins exert their cryoprotective effects.

MAIN RESULTS AND THE ROLE OF CHANCE

The secondary structures of AfrLEA2 and AfrLEA3m proteins were shown to consist of a large number of α-helices and the proteins were shown to be highly hydrophilic, in agreement with previous reports. Confocal microscopy results showed that the immunofluorescence of AfrLEA2-FITC and AfrLEA3m-FITC-labeled proteins appeared to be extracellular and did not penetrate the cell membrane compared with the fluorescein isothiocyanate (FITC) control group, indicating that both AfrLEA2 and AfrLEA3m proteins were extracellular. The group treated with 100 µg/mL AfrLEA2 or AfrLEA3m protein had more uniform cytoplasmic particles and fewer vacuoles compared to the 10 and 200 µg/mL groups and were closest to the fresh group. In the 100 µg/mL groups, MMPs were significantly higher while ROS and calcium levels were significantly lower than those in the control group and were closer to the levels observed in fresh oocytes. Meanwhile, 100 µg/mL of AfrLEA2 or AfrLEA3m protein caused smaller ice crystal formation in the IRI assay compared to the control group treated with dimethylsulphoxide (DMSO) and ethylene glycol (EG); thus, the recrystallization inhibition was superior to that with the conventional cryoprotectants DMSO and EG. Further results revealed that the proteins improved the developmental potential of human oocytes following cryopreservation, likely by downregulating FOS genes and reducing oxidative stress.

LIMITATIONS, REASONS FOR CAUTION

The in vitro-matured metaphase II (IVM-MII) oocytes used in the study, due to ethical constraints, may not accurately reflect the condition of MII oocytes in general. The AfrLEA2 and AfrLEA3m proteins are recombinant proteins and their synthetic stability needs to be further explored.

WIDER IMPLICATIONS OF THE FINDINGS

LEA proteins, as a non-toxic and effective cryoprotectant, can reduce the cryoinjury of oocytes during cryopreservation. It provides a new promising method for cryopreservation of various cell types.

STUDY FUNDING/COMPETING INTEREST(S)

This work was supported by the National Key Research and Development Program of China (2022YFC2703000) and the National Natural Science Foundation of China (52206064). The authors declare no competing interest.

TRIAL REGISTRATION NUMBER

N/A.

Effect of various contraceptives on oocyte yield and maturation in patients undergoing planned oocyte cryopreservation

RESEARCH QUESTION

Do the various forms of hormonal and non-hormonal contraceptives have any association with ovarian stimulation outcomes, such as oocyte yield and maturation, in patients undergoing planned oocyte cryopreservation (POC)?

DESIGN

This retrospective cohort study included all patients who underwent POC cycles between 2011 and 2023. The use of types of contraception before a POC cycle was recorded. The study evaluated the median number of cumulus-oocyte complexes obtained after vaginal oocyte retrieval and the proportion of metaphase II oocytes that underwent vitrification among all the cohorts.

RESULTS

A total of 4059 oocyte freezing cycles were included in the analysis. Eight types of contraceptive method were recognized in patients undergoing ovarian stimulation: intrauterine device (IUD), copper (n = 84); IUD, levonorgestrel low dose (<52 mg) (n = 37); IUD, levonorgestrel (n = 192); subdermal etonogestrel implant (n = 14); injectable medroxyprogesterone acetate (n = 11); etonogestrel vaginal ring (n = 142); combined oral contraceptive pills (n = 2349); and norelgestromin transdermal patch (n = 10). The control group included patients not using contraceptives or using barrier or calendar methods (n = 1220). Among all the cohorts the median number of cumulus-oocyte complexes retrieved during oocyte retrieval was comparable (P = 0.054), and a significant difference in oocyte maturity rate with median number of vitrified oocytes was found (P = 0.03, P < 0.001, respectively). After adjusting for confounders a multivariate analysis found no association between the type of contraceptive and proportion of metaphase II oocytes available for cryopreservation.

CONCLUSIONS

Among the various forms of contraception, none was shown to have an adverse association with oocyte yield or maturation rate in patients undergoing POC.

Providers' attitudes towards payment to egg donors: an international survey

The research question 'How do fertility professionals worldwide perceive the issue of payment for egg donation and does this view change under different circumstances?' was addressed. A worldwide online survey was conducted between January and March 2023, focusing on the views of fertility providers concerning egg donor payments. From the 3,790 IVF-Worldwide.com members invited, 532 (14%) from 88 countries responded. The majority of participants, primarily from Europe (38.9%) and Asia (20.1%), were fertility specialists, embryologists, and fertility nurses. Most (60.3%) favoured regulated donor compensation, with only 13% advocating for unrestricted amounts. Compensation opposition (22.4%) was often rooted in concerns about donors' best interests. When considering egg donation from low-resource to high-resource countries, 38.5% were opposed. When asked about compensating women who underwent elective, non-medical egg freezing should they choose to donate their unused oocytes, most responders supported it to some degree, with only 28.4% opposing any compensation. The survey revealed that a significant majority of fertility professionals worldwide are supportive of some form of compensation for egg donors. However, perspectives diverge depending on the specific scenario and the country of practice.

Reimbursement of elective egg freezing from health care systems: Beyond simplistic claims

France is the first country to offer elective egg freezing for nonmedical reasons under public health coverage. However, this decision deserves in‐depth scrutiny in the future because the cost‐beneficial profile is yet unknown.

Medroxyprogesterone acetate: an alternative to GnRH-antagonist in oocyte vitrification for social fertility preservation and preimplantation genetic testing for aneuploidy

RESEARCH QUESTION

Can medroxyprogesterone acetate (MPA) be used as a pituitary suppressor instead of a gonadotrophin releasing hormone (GnRH) antagonist during ovarian stimulation in elective fertility preservation and preimplantation genetic testing for aneuploidy (PGT-A) cycles?

DESIGN

A multicentre, retrospective, observational, cohort study conducted in 11 IVIRMA centres affiliated to private universities. Of a total of 1652 cycles of social fertility preservation, 267 patients were stimulated using a progestin-primed ovarian stimulation protocol (PPOS), and 1385 patients received a GnRH antagonist. In the PGT-A cycles, 5661 treatments were analysed: 635 patients received MPA and 5026 patients received GnRH antagonist. A further 66 fertility preservation and 1299 PGT-A cycles were cancelled. All cycles took place between June 2019 and December 2021.

RESULTS

In the social fertility preservation cycles, the number of mature oocytes vitrified in MPA was similar to the number of those treated with an antagonist, a trend that was seen regardless of age (≤35 or >35 years). In the PGT-A cycles, no differences were found in number of metaphase II, two pronuclei, number of biopsied embryos (4.4 ± 3.1 versus 4.5 ± 3.1), rate of euploidy (57.9% versus 56.4%) or ongoing pregnancy rate (50.4% versus 47.1%, P = 0.119) between the group receiving MPA versus a GnRH antagonist, whereas the clinical miscarriage rate was higher in the antagonist group (10.4% versus 14.8%, P = 0.019).

CONCLUSIONS

Administration of PPOS yields similar results to GnRH antagonists in oocytes retrieved, rate of euploid embryos and clinical outcome. Hence, PPOS can be recommended for ovarian stimulation in social fertility preservation and PGT-A cycles, as it allows greater patient comfort.

Cryopreservation: A Comprehensive Overview, Challenges, and Future Perspectives

Cryopreservation is the most prevalent method of long-term cell preservation. Effective cell cryopreservation depends on freezing, adequate storage, and correct thawing techniques. Recent advances in cryopreservation techniques minimize the cellular damage which occurs while processing samples. This article focuses on the fundamentals of cryopreservation techniques and how they can be implemented in a variety of clinical settings. The article presents a brief description of each of the standard cryopreservation procedures, such as slow freezing and vitrification. Alongside that, the membrane permeating and nonpermeating cryoprotectants are briefly discussed, along with current advancements in the field of cryopreservation and variables influencing the cryopreservation process. The diminution of cryoinjury incurred by the cell via the resuscitation process will also be highlighted. In the end application of cryopreservation techniques in many fields, with a special emphasis on stem cell preservation techniques and current advancements presented. Furthermore, the challenges while implementing cryopreservation and the futuristic scope of the fields are illustrated herein. The content of this review sheds light on various ways to enhance the output of the cell preservation process and minimize cryoinjury while improving cell revival.

Summary of the ISFP congress, Brussels, 10-12 November, 2022

The 7th International Congress of the ISFP was held in Brussels in November 2022. Hundreds of attendees from all over the world had the rare opportunity to hear the most distinguished leaders discuss and debate the latest advances in the field. Participants were also able to attend workshops under the guidance of skilled practitioners. Numerous topics were considered, including a recap on fertility preservation approaches in cancer and benign pathologies and a section on male factor infertility. Other aspects covered were in vitro maturation and poor responders, the impact of chemotherapy on the ovary, and future perspectives. Participants had the chance to listen to a symposium on fertility preservation techniques, and finally, a keynote lecture on fertility preservation in gynecological cancers brought this prominent and highly influential event to a close.

Shared intent in third-party donation will underpin the success of new surrogacy laws

The demands for surrogacy treatments continue to grow worldwide. However the legal guidance for non-commercial surrogacy treatments remains inadequate, and this commentary argues how the forthcoming guidance on surrogacy from the UK Law Commissions would benefit from a bold decision based on previous experience derived from similar developments in three other areas of assisted conception.