Current trends and progress in clinical applications of oocyte cryopreservation

Equilibrium vitrification of oocytes using low concentrations of cryoprotectants

In order to make dry ice transportation of vitrified embryos practical, a near-equilibrium vitrification was developed using a cryoprotectant solution (EDFS10/10a), by which mouse embryos at various stages were vitrified in a near-equilibrium environment. EDFS10/10a consisted of 10% (v/v) ethylene glycol, 10% (v/v) Me2SO, 0.4 M sucrose and 24% (w/v) Ficoll PM70. This method exhibited the benefits of slow freezing and vitrification, with a low risk of osmotic injury. In this study, we investigated whether mouse oocytes are vitrifiable with EDFS10/10a in a highly dehydrated/concentrated state, and whether they can remain fertilizable and developing into embryos after vitrification. When mature mouse oocytes were vitrified in liquid nitrogen and after 4-28 days of storage at -80 °C, high survival rates were observed (88-99%). Vitrified and warmed oocytes were subjected to partial zona dissection and in vitro fertilized. The rate of 2-cell stage was 80-82%. Blastocyst formation rate was 55-70% which was similar to that of embryos derived from fresh oocytes. After the 2-cell embryos were transferred to recipient mice, the implantation and offspring rates did not differ significantly from those of embryos derived from fresh oocytes, indicating that vitrified oocytes retained the developmental ability. Therefore, it is possible to vitrify mouse oocytes in a near-equilibrium state using EDFS10/10a and conveniently transported using dry ice.

State of the art in assisted reproductive technologies for patients with advanced maternal age

According to the World Health Organization, the female reproductive age lasts up to 49 years, but problems with the realization of women's reproductive rights may arise much earlier. Significant numbers of factors affect the state of reproductive health: socioeconomic, ecological, lifestyle features, the level of medical literacy, and the state of the organization and medical care quality. Among the reasons for fertility decline in advanced reproductive age are the loss of cellular receptors for gonadotropins, an increase in the threshold of sensitivity of the hypothalamic-pituitary system to the action of hormones and their metabolites, and many others. Furthermore, negative changes accumulate in the oocyte genome, reducing the possibility of fertilization, normal development and implantation of the embryo and healthy offspring birth. Another theory of ageing causing changes in oocytes is the mitochondrial free radical theory of ageing. Taking into account all these age-related changes in gametogenesis, this review considers modern technologies aimed at the preservation and realization of female fertility. Among the existing approaches, two main ones can be distinguished: methods allowing the preservation of reproductive cells at a younger age using ART intervention and cryobanking, as well as methods aimed at improving the basic functional state of advanced-age women's oocytes and embryos.

The Effect of Freezing Twice during Assisted Reproductive Technology on Perinatal and Neonatal Outcomes

Objective

The aim of this paper was to investigate whether two freeze-thaw cycles before embryo transfer may affect perinatal and neonatal outcomes.

Materials and Methods

A total of 8,028 frozen-thawed embryo transfer patients who became pregnant between March 2013 and September 2019 were included. The patients were divided into two groups: the oocyte cryopreservation (OC) group (N = 96) and the control group (N = 7932). Propensity score matching (PSM) was used to adjust the baseline characteristics of the two groups at a proportion of 1 : 4. There were 96 patients in the OC group and 369 patients in the control group after PSM. The pregnancy-related complications and neonatal conditions after delivery of the two groups were compared.

Results

The OC group had a higher stillbirth rate (3.1% vs. 0.3%, P = 0.029) than the control group after PSM. Moreover, a slightly higher pregnancy defect rate was found in the OC group. There was no significant difference in the rates of diabetes mellitus, hypertension during pregnancy, cesarean section, multiple births, low birth weight (LBW), or premature birth defects between the two groups.

Conclusions

Our findings demonstrate that performing frozen-thawed embryo transfer (FET) with cryopreserved oocytes was associated with a higher rate of stillbirth than FET with fresh oocytes. The incidences of diabetes, gestational hypertension, cesarean section, multiple births, LBW, premature birth, and birth defects of the two groups were not significantly different.

An Eight Year Experience of Autologous Oocyte Vitrification for Infertile Patients Owing to Unavailability of Sperm on Oocyte Retrieval Day

Objective: The objective of this study was to provide a descriptive analysis of the clinical outcomes achieved in oocyte vitrification in cases where sperm was unavailable on oocyte retrieval day, and to identify predictors of oocyte survival. Methods: This retrospective cohort study used data from a university-affiliated reproductive medical center. There were 321 cycles in which some of, or all oocytes were vitrified owing to the unavailability of sperm between March 2009 and October 2017. A descriptive analysis of the clinical outcomes including both fresh embryo transfers and cryopreserved embryo transfers was provided. The ability of an individual parameter to forecast oocyte survival per thawing cycle was assessed by binary logistic regression analysis. The cumulative probability of live birth (CPLB) was estimated by using the Kaplan-Meier method according to the total number of oocytes thawed in consecutive procedures. Results: The average survival rate was 83.13%. High-quality embryo rate and blastocyst rate decreased significantly decreased significantly in vitrification oocyte group compared to fresh control oocytes. The comparison of sibling oocytes in part-oocyte-vitrified cycles shows fewer high-quality embryos developed in the vitrified group. The live birth rate per warmed-oocyte was 4.3%. Reasons for lack of sperm availability on oocyte retrieval day and serum cholesterol levels were found to be associated with oocyte survival rate in the present study. Kaplan-Meier analysis showed no significant difference in CPLB between patients ≤35 vs. >35 years. Conclusions: Oocyte vitrification is an indispensable and effective alternative when sperm are not available on oocyte retrieval day. The present study provided evidence that oocytes from infertile couples were more likely to suffer oocyte/embryo vitrification injury. Clinicians need to take this into account when advising patients in similar situations. Further studies will be necessary to clarify the correlation between serum metabolism parameters and human oocyte survival after vitrification.

Oocyte Cryopreservation in Domestic Animals and Humans: Principles, Techniques and Updated Outcomes

Oocyte cryopreservation plays important roles in basic research and the application of models for genetic preservation and in clinical situations. This technology provides long-term storage of gametes for genetic banking and subsequent use with other assisted reproductive technologies. Until recently, oocytes have remained the most difficult cell type to freeze, as the oocytes per se are large with limited surface area to cytoplasm ratio. They are also highly sensitive to damage during cryopreservation, and therefore the success rate of oocyte cryopreservation is generally poor when compared to noncryopreserved oocytes. Although advancement in oocyte cryopreservation has progressed rapidly for decades, the improvement of cryosurvival and clinical outcomes is still required. This review focuses on the principles, techniques, outcomes and prospects of oocyte cryopreservation in domestic animals and humans.

Current perspectives on social oocyte freezing

Demand for oocyte freezing in absence of a medical indication is growing as women delay childbirth and seek to extend the window of opportunity for parenthood. The optimum age for oocyte freezing is below 35 years, whereas currently the mean age of women undergoing oocyte freezing in the UK is 38 years. Nearly half of women undergoing oocyte freezing are not in a relationship. The treatment is not publicly funded and the average price for a complete oocyte freezing and thawing cycle, including annual storage fees, could reach over £7000. The live birth rate per oocyte thaw cycle is 18% and is influenced by age at the time of oocyte freezing. Women considering social oocyte freezing should be thoroughly counselled about the efficacy, limitations, cost implications and alternatives to oocyte freezing and provided with the appropriate support to enable a truly informed reproductive choice.

Oocyte cryopreservation - current scenario and future perspectives: A narrative review

Oocyte cryopreservation is a boon for women undergoing assisted reproductive technology. With the evolution in the technique of cryopreservation over the last three decades, there has been an exponential rise in the number of oocyte cryopreservation cycles for diverse indications. Apart from cancer patients, it has also been promoted as a mode of fertility insurance to overcome the age-related decline in fertility as well as post-surgical decline following endometriosis surgery. The objective of the review is to evaluate its clinical applications, ideal age at freezing, optimal oocyte number, freezing method of choice, efficacy, safety and recent advances. In the last decade, vitrification has surpassed slow freezing for oocyte cryopreservation. Although closed system of vitrification provides the aseptic environment, open vitrification is commonly followed in practice. Early to mid-thirties is a reasonable age group for planned oocyte cryopreservation, although it might be recommended at a younger age, in patients with diminished ovarian reserve. The patients should be motivated to preserve around 14–20 mature oocytes for successful live birth. Various studies have shown comparable fertilisation and pregnancy rates between Intracytoplasmic sperm injection with fresh and frozen-thawed oocytes. The available evidence has shown no increase in the incidence of congenital abnormalities in babies born through vitrified oocytes. In the future, image analysis using artificial intelligence, and spindle visualisation using poloscope may further enhance the outcome of oocyte cryopreservation.

Cryopreserved Gamete and Embryo Transport: Proposed Protocol and Form Templates-SIERR (Italian Society of Embryology, Reproduction, and Research)

Introduction: In Italy, the transport of cryopreserved biological material is controlled by several Decrees (Legislative Decree No. 191/2007 and No. 16/2010 and Health Ministry's Decree of October 10, 2012). Given the nature of their applications, the transport of reproductive cells has peculiar quality and safety requirements that must be applied universally, minimizing the chance of error. To standardize the cross-border shipping procedure to meet the quality, traceability, and safety criteria for cells and tissues, it is appropriate to establish a unified process using the same tools, forms, and communication channels. Methods: A working group has been created by SIERR. This "FOCUS Group" was constituted by representatives from Italian-assisted reproductive technology centers and sperm banks who worked together to define joint procedural steps and create specific forms to support the movement of cryopreserved samples. Results: The FOCUS Group identified the critical steps in the communication procedures between Italian centers and created the related forms: patient authorization, request from the recipient center, critical checks carried out by both sending and recipient centers, start of samples transfer, collection, transport and taking responsibility of the biological material, acknowledgment of samples arrival, and acknowledgement of any adverse event that occurred. Discussion: Indications on shipping between tissue institutions and legal responsibilities are important points and a working protocol with shared transport forms has been defined. Standard Operating Procedures are necessary in light of the increasingly widespread movement of biological samples between the various countries, and represent a valid means of support for the patients who could have a higher awareness of safety and traceability during each stage of gamete transport.

Self-reported quality of life scales in women undergoing oocyte freezing versus in vitro fertilization

PURPOSE

The objective of this study was to investigate stress levels among women undergoing elective oocyte cryopreservation by comparing their self-reported quality of life measures with women undergoing in vitro fertilization during the fertility treatment cycle.

METHODS

Patients undergoing oocyte retrieval at a single institution were offered a voluntary, anonymous, and written questionnaire. The survey was adapted and validated from the Fertility Quality of Life tool to assess self-reported fertility treatment-related problems and was tested for construct validity and reliability. Based on exploratory factor analyses, three subscales were created as follows: fertility treatment-related stress, tolerability, and environment. Relationships between patient characteristics and fertility treatment-related measures were examined with Fisher's exact test, ANOVA, and multivariate regression with significance p < 0.05.

RESULTS

A total of 461 patients (331 IVF, 130 egg freeze) were included in the analysis. Medically indicated egg freezing patients were excluded. Overall, both IVF and egg freeze patients reported stress during the current fertility cycle and there were no significant differences between IVF and egg freeze patients for any subscale scores. Three sets of generalized linear models were run and found age to be associated with fertility treatment-related stress and tolerability scores, with younger patients experiencing greater difficulties. Additionally, patients who underwent repeat cycles reported more fertility treatment-related stress.

CONCLUSIONS

Patients undergoing egg freezing have similar responses to quality of life questions as patients undergoing IVF. Repeat cycles and younger age contribute to perceptions of stress. This information supports developing stress reduction strategies for all women undergoing egg freezing.

A Practical Guide to Gynecologic and Reproductive Health in Women Undergoing Hematopoietic Stem Cell Transplant

Optimum care of female transplant recipients requires gynecologic care at several stages through the allogeneic hematopoietic stem cell transplantation (HCT) process. Sex-based considerations in women post-HCT span gynecologic sequelae of transplant along with assessment and maintenance of optimal sexual and gynecologic health. Pre-HCT, managing menstruation and abnormal uterine or genital bleeding, considering fertility preservation, and assessing for sexually transmitted infections, including human papillomavirus (HPV)-related disease and cervical cancer, enhance women's health. While inpatient during transplant when women are thrombocytopenic, menstrual bleeding requires suppression. Whenever graft-versus-host disease (GVHD) is assessed, screening for genital GVHD merits consideration. After the first 100 days, periodic assessments include obtaining a menstrual history, assessing ovarian function, and reviewing current hormonal use and contraindications to hormonal methods. Regular assessment for primary ovarian insufficiency, dyspareunia, and intimacy guides provision of contraception and hormone replacement options. As part of ongoing screening for genital GVHD and HPV-related disease, including sexually transmitted infections, periodic pelvic examinations are performed. Once successful long-term survival is achieved, planning for fertility may be considered. This article offers a comprehensive approach to these aspects of gynecologic care of patients throughout the trajectory of HCT and beyond into survivorship. We review the effects of HCT treatment on sexual health, ovarian function, and resulting menstrual changes and fertility challenges. Identification, treatment, and prevention of subsequent malignancies, including breast cancer, are discussed, with a focus on regular assessment of genital HPV disease and GVHD in long-term follow-up.

Knowledge and decision making about future fertility and oocyte cryopreservation among young women

The objective was to examine what young graduate student women know about preserving fertility/oocyte cryopreservation, and which reproductive resources they use. A prospective, cross-sectional design was used and the study was conducted at a University on the East Coast of the United States. The participants were 278 female graduate students. Participants completed a survey with questions about demographics, fertility knowledge, oocyte cryopreservation, and sources of fertility information. Descriptive statistics were calculated for all variables. Participants had average knowledge about fertility (64% items correct). The most used fertility information source was formal education (87.1%), information to help make fertility decisions was gynaecologists (85.3%), and oocyte cryopreservation was media (63.4%). Only 26.6% reported being well informed about fertility. Although 93.9% had heard of oocyte cryopreservation, only 7.2% had considered its use. Most (74.9%) ranked fertility as important, though 83% would consider postponing family until career (85.2%) and relationship (85.2%) were established. Half felt that there was a social stigma surrounding oocyte cryopreservation, and 70.1% believed that the media gives the impression that motherhood is viable after 40 years old. Professionally motivated women receive the most information about fertility from formal, accuracy-driven sources (i.e. education, healthcare providers), but information about fertility preservation from media. They lack knowledge about fertility planning.

Reproductive experiences of women who cryopreserved oocytes for non-medical reasons

STUDY QUESTION

What are the reproductive experiences of women who cryopreserve oocytes for non-medical reasons?

SUMMARY ANSWER

One in three women had been pregnant at some stage in their lives and while most still wanted to have a child or another child, very few had used their stored oocytes, predominantly because they did not want to be single parents.

WHAT IS KNOWN ALREADY

The number of healthy women who freeze oocytes to avoid age-related infertility is increasing. Evidence about reproductive outcomes after oocyte cryopreservation for non-medical reasons is needed to help women make informed decisions.

STUDY DESIGN SIZE, DURATION

A cross-sectional survey was carried out. Study packs which included a self-administered questionnaire were mailed by clinic staff to 193 eligible women.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Women who had stored oocytes for non-medical reasons at Melbourne IVF, a private ART clinic, between 1999 and 2014 were identified from medical records and invited to complete an anonymous questionnaire about their reproductive histories and experience of oocyte cryopreservation.

MAIN RESULTS AND THE ROLE OF CHANCE

A total of 10 survey packs were returned to the clinic marked 'address unknown'. Of the 183 potential respondents, 96 (53%) returned the questionnaire. One respondent provided only free-text comments, thus data from 95 respondents were compiled. The mean age at the time of freezing oocytes was 37.1 years (SD ± 2.6, range: 27-42) and the average number of oocytes stored was 14.2 (SD ± 7.9, range: 0-42); 2% had attempted to store oocytes but had none suitable for freezing, 24% had stored <8 oocytes, 35% had 8-15, 25% had 16-23 and 14% had stored >23 oocytes. About one-third of respondents (34%) had been pregnant at some point in their lives. Six women (6%) had used their stored oocytes and three of them had given birth as a result. The main reason for not using stored oocytes was not wanting to be a single parent. Of the 87 (91%) women who still had oocytes stored, 21% intended to use them while 69% indicated that their circumstances would determine usage. The mean number of children respondents would ideally have liked to have was significantly higher than the number of children they expected to have (2.11 versus 1.38, P < 0.001).

LIMITATIONS, REASONS FOR CAUTION

The limitations are inherent to any anonymously completed questionnaire: participation bias, missing data and the possibility that some questions or response alternatives may have been ambiguous.

WIDER IMPLICATIONS OF THE FINDINGS

The findings add to the very limited evidence about the reproductive outcomes experienced by women who freeze oocytes for non-medical reasons and can be used to help women make informed decisions about whether to store oocytes.

STUDY FUNDING/COMPETING INTEREST(S)

The study was funded by Melbourne IVF. K.H. has received honoraria from Merck-Serono, J.M. is a clinician at Melbourne IVF, F.A. is a Melbourne IVF employee, J.F. is supported by a Monash Professorial Fellowship and the Jean Hailes Professorial Fellowship which receives funding from the L and H Hecht Trust, managed by Perpetual Trustees Pty Ltd. M.K., N.P., M.H., M.P. and C.B. have no competing interests.

TRIAL REGISTRATION NUMBER

Not applicable.

RNA-Seq transcriptome profiling of mouse oocytes after in vitro maturation and/or vitrification

In vitro maturation (IVM) and vitrification have been widely used to prepare oocytes before fertilization; however, potential effects of these procedures, such as expression profile changes, are poorly understood. In this study, mouse oocytes were divided into four groups and subjected to combinations of in vitro maturation and/or vitrification treatments. RNA-seq and in silico pathway analysis were used to identify differentially expressed genes (DEGs) that may be involved in oocyte viability after in vitro maturation and/or vitrification. Our results showed that 1) 69 genes were differentially expressed after IVM, 66 of which were up-regulated. Atp5e and Atp5o were enriched in the most significant gene ontology term “mitochondrial membrane part”; thus, these genes may be promising candidate biomarkers for oocyte viability after IVM. 2) The influence of vitrification on the transcriptome of oocytes was negligible, as no DEGs were found between vitrified and fresh oocytes. 3) The MII stage is more suitable for oocyte vitrification with respect to the transcriptome. This study provides a valuable new theoretical basis to further improve the efficiency of in vitro maturation and/or oocyte vitrification.

Safety and efficiency of oocyte vitrification

As the oocyte is the starting point for a new life, artificial reproductive technology (ART) techniques should not affect the (ultra) structural and functional integrity, or the developmental competence. Oocyte vitrification -one of the most significant achievements in human ART during the past decade- should therefore be a safe and efficient technique. This review discusses the principles and developments of the existing and future techniques, applications possibilities and safety concerns. The broad range of vitrification media and devices that are currently available, show differences in their effects on the oocyte ultrastructure and preimplantation development. It is not yet fully decided whether this has an influence on the obstetric and neonatal outcome, since only limited information is available with different media and devices. For autologous oocytes, the obstetric and neonatal outcomes appear promising and comparable to pregnancies obtained with fresh oocytes. This however, is not the case for heterologous fresh or vitrified oocytes, where the immunological foreign foetus induces adverse obstetric and neonatal outcomes. Besides the oocyte vitrification process itself, the effect of multiple stimulations (for oocyte banking or for oocyte donors), seems to influence the possibility to develop gynaecological cancers further in life. Automated vitrification/warming should offer a consistent, cross-contamination free process that offers the highest safety level for the users. They should also produce more consistent results in survival, development and clinical pregnancies between different IVF clinics.

Freeze/thaw stress induces organelle remodeling and membrane recycling in cryopreserved human mature oocytes

PURPOSE

Our aim was to evaluate the ultrastructure of human metaphase II oocytes subjected to slow freezing and fixed after thawing at different intervals during post-thaw rehydration.

METHODS

Samples were studied by light and transmission electron microscopy.

RESULTS

We found that vacuolization was present in all cryopreserved oocytes, reaching a maximum in the intermediate stage of rehydration. Mitochondria-smooth endoplasmic reticulum (M-SER) aggregates decreased following thawing, particularly in the first and intermediate stages of rehydration, whereas mitochondria-vesicle (MV) complexes augmented in the same stages. At the end of rehydration, vacuoles and MV complexes both diminished and M-SER aggregates increased again. Cortical granules (CGs) were scarce in all cryopreserved oocytes, gradually diminishing as rehydration progressed.

CONCLUSIONS

This study also shows that such a membrane remodeling is mainly represented by a dynamic process of transition between M-SER aggregates and MV complexes, both able of transforming into each other. Vacuoles and CG membranes may take part in the membrane recycling mechanism.

Blurring the line between life and death: a review of the psychological and ethical concerns related to posthumous-assisted reproduction

Posthumous-assisted reproduction (PAR), though viewed unfavourably by some, is desirable to many individuals whose partners die prior to the completion of family building. PAR is technically feasible for males and females both pre- and post-mortem and these procedures have previously been completed on numerous occasions. However, such treatment is associated with three primary ethical concerns: autonomy; beneficence; and justice for the living, the deceased, and the soon-to-be conceived. Further, there are many psychological risks of PAR which may affect all involved parties. As such, early psychological counselling of patients and surviving family members is warranted.

Prophylactic oophorectomy for hereditary small cell carcinoma of the ovary, hypercalcemic type

•Prophylactic oophorectomy can prevent small cell carcinoma of the ovary, hypercalcemic type in carriers of germline SMARCA4 mutations.•Unaffected SMARCA4 mutation carriers who desire children may be best served by oocyte cryopreservation prior to prophylactic oophorectomy.

Referral for fertility preservation counselling in female cancer patients

STUDY QUESTION

What changes can be detected in fertility preservation (FP) counselling (FPC) over time and what are the determinants associated with the referral of newly diagnosed female cancer patients, aged 0-39 years, to a specialist in reproductive medicine for FPC?

SUMMARY ANSWER

Although the absolute number of patients receiving FPC increased over time, only 9.8% of all potential patients (aged 0-39 years) were referred in 2011 and referral disparities were found with respect to patients' age, cancer diagnosis and healthcare provider-related factors.

WHAT IS KNOWN ALREADY

Referral rates for FPC prior to the start of gonadotoxic cancer treatment are low. Determinants associated with low referral and referral disparities have been identified in previous studies, although there are only scarce data on referral practices and determinants for FPC referral in settings with reimbursement of FP(C).

STUDY DESIGN, SIZE, DURATION

We conducted a retrospective observational and questionnaire study in a Dutch university hospital. Data on all female cancer patients counselled for FP in this centre (2001-2013), as well as all newly diagnosed female cancer patients aged 0-39 years in the region (2009-2011) were collected.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Data were retrieved from medical records (FPC patients), cancer incidences reported by the Dutch Cancer Registry (to calculate referral percentages) and referring professionals (to identify reasons for the current referral behaviour).

MAIN RESULTS AND THE ROLE OF CHANCE

In 2011, a total of 9.8% of the patients were referred for FPC. Patients aged 20-29 years or diagnosed with breast cancer or lymphoma were referred more frequently compared with patients under the age of 20 years or patients diagnosed with other malignancies. The absolute numbers of patients receiving FPC increased over time. Healthcare provider-related determinants for low referral were not starting a discussion about fertility-related issues, not knowing where to refer a patient for FPC and not collaborating with patients' associations.

LIMITATIONS, REASONS FOR CAUTION

Actual referral rates may slightly differ from our estimation as there may have been patients who did not wish to receive FPC. Sporadically, patients might have been directly referred to other regions or may have received ovarian transposition without FPC. By excluding skin cancer patients, we will have underestimated the group of women who are eligible for FPC as this group also includes melanoma patients who might have received gonadotoxic therapy.

WIDER IMPLICATIONS OF THE FINDINGS

The low referral rates and referral disparities reported in the current study indicate that there are opportunities to improve referral practices. Future research should focus on the implementation and evaluation of interventions to improve referral practices, such as information materials for patients at oncology departments, discussion prompts or methods to increase the awareness of physicians and patients of FP techniques and guidelines.

STUDY FUNDING/COMPETING INTERESTS

This work was supported by the Radboud university medical center and the Radboud Institute for Health Sciences. The authors have declared no conflicts of interest with respect to this work.

TRIAL REGISTRATION NUMBER

Not applicable.