Over 900 oocyte cryopreservation babies born with no apparent increase in congenital anomalies

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.

On Ice: The impact of vitrification on the use of eggs in fertility treatment

The possibility to freeze sperm and embryos has long been available to men and women facing infertility as a result of an illness or medical treatment. However, the ability to successfully cryopreserve human eggs is comparatively recent. The introduction and increasing use of egg vitrification from the mid-2000s onwards, alongside the use of intracytoplasmic sperm injection, has seen improved ongoing clinical pregnancy rates compared with slow freezing methods. Despite concerns, the technology has been widely embraced by the scientific community and in recent years has been applied in a greater variety of contexts. In this short perspective paper, we consider two specific applications for the vitrification of human eggs in routine assisted reproduction practice: social egg freezing and the use of frozen eggs in egg donation. We suggest that vitrification is transforming the reproductive landscape in novel and complex ways and that we must be alert to the challenges, complexities and ethics of such developments, especially for those who may be excluded or marginalised by these techniques.

The number of oocytes associated with maximum cumulative live birth rates per aspiration depends on female age: a population study of 221 221 treatment cycles

STUDY QUESTION

What is the number of oocytes where the maximum cumulative live birth rate per aspiration (CLBR) is observed during ART in women of different ages?

SUMMARY ANSWER

The maximum CLBR was observed when around 25 oocytes were retrieved in women between 18-35 years of age, around 9 oocytes in women more than 45 years of age and continued to increase beyond 30 oocytes in women between 36-44 years of age.

WHAT IS KNOWN ALREADY

The live birth rate per fresh or frozen/thaw embryo transfer (FET) procedure has traditionally been the main measure of ART success. However, with the introduction of highly efficient embryo cryopreservation methods, CLBR encompassing live delivery outcomes from the fresh and all subsequent FET following a single ovarian stimulation and oocyte collection is increasingly viewed as a more meaningful measure of treatment success. There is evidence suggesting that larger oocyte yields are associated with increased likelihood of cumulative live birth per aspiration. Whether this association is the same across female ages has not yet been properly investigated.

STUDY DESIGN, SIZE, DURATION

This is a large retrospective population-based cohort study using data from the Australian and New Zealand Assisted Reproduction Database (ANZARD). ANZARD contains information from all ART treatment cycles carried out in all fertility centres in Australia and New Zealand. Overall, 221 221 autologous oocyte aspiration cycles carried out between January 2009 to December 2015 were included in the analysis.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Cumulative live birth per aspiration was defined as at least one liveborn baby at ≥20 weeks gestation resulting from an ART aspiration cycle, including all fresh and FET resulting from the associated ovarian stimulation, until one live birth occurred or all embryos were used. Cycles where no oocytes were retrieved were excluded from analysis as there is no possibility of live birth. Analyses of data were performed using generalized estimating equations to account for the clustered nature of data (multiple cycles undertaken by a woman). Univariate and multivariable regression analysis was performed to identify and adjust for factors known to independently affect cumulative live birth per aspiration. An interaction term between female age and the number of oocytes retrieved was included to assess whether the age of the women was associated with a different optimal number of oocytes to achieve at least one live birth from an aspiration cycle (i.e. the effect-modifying role of female age). The likelihood of cumulative live birth per aspiration was calculated as odds ratios (ORs) with 95% CI.

MAIN RESULTS AND THE ROLE OF CHANCE

The median number of oocytes retrieved was 7 (interquartile range, 4-12) and median age of patients was 36 (interquartile range, 33-40). The overall CLBR was 32.2%. The results from the multivariable regression analysis showedthat the number of oocytes retrieved remained a significant predictor (P < 0.001) of cumulative live birth per aspiration after adjusting for female age, parity and cycle count. Compared to the reference group of 10-14 oocytes retrieved, the adjusted odds for cumulative live birth per aspiration increased with the number of oocytes retrieved: 1-3 oocytes, 0.21 (95% CI, 0.20-0.22); 4-9 oocytes, 0.56 (95% CI, 0.55-0.58); 15-19 oocytes, 1.38 (95% CI, 1.34-1.43); 20-24 oocytes, 1.75 (95% CI, 1.67-1.84); and 2.10 (95% CI, 1.96-2.25) with more than 25 oocytes. After stratifying by female age group, the rate of increase in CLBR per additional oocyte retrieved was lower in the older age groups, indicating that higher oocyte yields were more beneficial in younger women. CLBR of patients in the <30 years and 30-34 years age groups appeared to reach a plateau (with only minimal increase in CLBR per additional oocyte retrieved) after retrieval of 25 oocytes at 73% and 72%, respectively, while CLBR of patients in the 35-39 years and 40-44 years age groups continued to increase with higher oocyte yields, reaching 68% and 40%, respectively, when 30 or more oocytes were retrieved. CLBR of patients aged 45 years and above remained consistently below 5%. Findings suggest that the number of oocytes retrieved where CLBR appears to be maximized is around 25 in women between 18-35 years, more than 30 in women between 36-44 years and around 9 in women 45 years and older. However, results for women aged 45 years and older may not be as robust due to the relatively small sample size available in this age group.

LIMITATIONS, REASONS FOR CAUTION

As with all large retrospective database studies, there are potential confounders that cannot be accounted for. Despite the current study being based on complete ascertainment of ART cycles across two countries, ovarian stimulation protocols, oocyte quality parameters and a number of important patient characteristics are not collected by ANZARD. Additionally, a small number of cycles were available for women over 45 years yielding more than 15 oocytes, making these estimates unreliable.

WIDER IMPLICATIONS OF THE FINDINGS

The results from this study demonstrate that the number of oocytes retrieved where the maximum CLBR is observed during ART is dependent on female age. This provides information for clinicians and patients to understand the modifying effect of age on the number of oocytes retrieved and the likelihood of success with ART.

STUDY FUNDING/COMPETING INTEREST(S)

No external funding was used for this study. The Fertility Society of Australia funds the National Perinatal Epidemiology and Statistics Unit to manage ANZARD and conduct national reporting of ART in Australia and New Zealand. Associate Professor Georgina Chambers (G.C.) is employed by the University of New South Wales (UNSW) and is director of the National Perinatal Epidemiology and Statistics Unit at UNSW. G.C. was also a paid member of the Australian governments Medicare Benefits Scheme taskforce on assisted reproductive technologies in 2017.

Cryopreservation of Mammalian Oocytes: Slow Cooling and Vitrification as Successful Methods for Cryogenic Storage

Two basic methods for the laboratory-focused cryopreservation of mammalian oocytes are described, based on work with murine oocytes. One method uses a relatively low concentration of the cryoprotectant propanediol plus sucrose and requires controlled rate cooling equipment to achieve a slow cooling rate. This method has also produced live births from cryopreserved human oocytes. The second method, which is described here, employs a high concentration of the cryoprotectant dimethyl sulfoxide plus a low concentration of polyethylene glycol. This is a vitrification method, which involves ultra-rapid cooling by plunging standard straws into liquid nitrogen vapor, hence avoiding the need for specialized equipment, but requires technical ability to manipulate the oocytes quickly in the highly concentrated cryoprotectant solutions. Murine oocytes that have been vitrified using this technique have resulted in live births. Vitrification using other cryoprotectant mixtures is now a popular clinically accepted method for cryobanking of human oocytes.

Preservation of fertility in patients with hematological malignancies

Oncofertility is the medical field that bridges oncology and reproduction that seeks to give healthcare providers and patients the opportunity to optimize residual fertility. The treatment for hematological malignancies carries gonadal toxicity, so that the preservation of fertility should be considered in all patients in childhood, adolescence and young adulthood. Most patients who receive only chemotherapy remain fertile, whereas those who receive regimens consisting of high-dose alkylating agents or total body irradiation can develop permanent infertility. In postpubertal patients, there are established methods for preserving fertility, such as the cryopreservation of sperm, oocytes and embryos. Although ideally performed before the initiation of gonadotoxic treatment, these procedures for fertility preservation can be performed any time prior to the loss of gonadal function. In contrast, a standard option is not available in prepubertal patients, and the preservation of fertility must be sought through experimental methods. Future advances in reproductive medicine may overcome this limitation. Gonadal tissue cryopreservation might be performed in the hope that sperm or mature oocytes could later be extracted from cryopreserved tissue. Healthcare providers, including hematologists, reproductive endocrinologists, nurses, clinical psychotherapists and embryologists, need to optimize the patient's fertility through shared decision-making while always remaining aware of the rapidly progressing developments in reproductive medicine.

Effects of oocyte vitrification on the behaviors and physiological indexes of aged first filial generation mice

To evaluate the long-term effects of oocyte cryopreservation on the health of the first filial generation (F1), we used B6D2F1 mice for oocyte collection, in vitro fertilization, and breeding. The female F1 mice born from the offspring of fresh mature oocytes (control group) and from the offspring of vitrified oocytes with traditional vitrification medium (VM group) and new improved vitrification medium (2P10E7D group) were maintained until 14-15 months of age for behavioral tests and 16-17 months of age for physiological analyses. Behavioral indexes, including anxiety-like status, discrimination ability, learning and memory ability, were investigated. Physiological indexes including body weight, body fat, heart rate, blood pressure, and blood lipids were also analyzed. In our results, the behavioral indexes, body weight, body fat, heart rate, blood pressure, total cholesterol (TC), high-density lipoprotein cholesterol (HDL), and low-density lipoprotein cholesterol (LDL) did not show significant differences among the three groups. However, the triglyceride (TG) level of the VM group was higher than that of the 2P10E7D group. Moreover, compared with the control group, both the VM group and the 2P10E7D group showed greatly increased diastolic blood pressure. This study is the first to report that oocyte vitrification might affect metabolic physiological indexes via transgenerational inheritance rather than behaviors related to anxiety-like status and cognitive ability. Furthermore, different vitrification media might have differential transgenerational effects.

Social freezing of oocytes: a means to take control of your fertility

In the last few decades, there have been tremendous developments of assisted reproductive technologies, but the outcome of in vitro fertilization is highly dependent on the age of the oocyte. The introduction of vitrification offers a possibility to freeze eggs proactively in younger years and use them at later ages, also called social egg freezing. Knowledge about age-related fertility decline is insufficient among many women, and there is an overoptimistic trust that in vitro fertilization can overcome this. The awareness of proactive egg freezing is limited, both among doctors and in the general population. This review aims at increasing the knowledge about proactive egg freezing and offers a means to advise women correctly. It deals with national guidelines, the best age and optimal number of eggs to freeze, and the chance to succeed. Creating more public awareness about age-linked fertility decline and elective egg freezing may help women reproduce at their own pace - to take control of their fertility.

Cryopreservation of human embryos and oocytes for fertility preservation in cancer and non cancer patients: a mini review

The term 'cryopreservation' illustrates the process of freezing cells and storing at very low temperature in liquid nitrogen (-196 °C). Cooling is not a physiological condition for human cells especially due to the high concentration of water in the living matter, whose conversion to ice crystals may be associated with cell death. Human oocytes are particularly sensitive to the freezing process, primarily because of their large size and the presence of the meiotic spindle, which at low temperature can degenerate. In the last decade, the cryopreservation technology has become highly important as an option for fertility preservation (FP) in women with cancer. Anticancer therapy might promote premature ovarian failure and negatively affects the reproductive outcome. Over the years, scientists have proposed different cryopreservation strategies in the effort to maintain the physiological functions of oocytes and embryo. However, despite the first success obtained in the 1980s with frozen oocytes, it was not until recently that a new approach has been proposed: the 'Vitrification' which allowed a breakthrough in this procedure. FP is a major determinant for cancer survivor women in the reproductive age. This article describes the FP options currently available, focusing mainly on oocyte and embryo cryopreservation.

Oocyte Vitrification: A Comparative Analysis Between Fresh and Cryopreserved Oocytes in an Oocyte Donation Program

Background: Oocyte Cryopreservation has become an important part of infertility treatment for various reasons such as fertility preservation in women going for oncological treatment; in oocyte donation cycles; in eliminating several religious, ethical, and legal concerns of embryo freezing and in women who wish to delay childbirth. The newer ”vitrification” technique for freezing has further improved the success rates for actual conception than the earlier method of slow freezing. A successful oocyte freezing program can help in establishment of oocyte banks, which would help to provide compatible oocytes immediately, thus would eliminate the several problems of fresh donor cycles.

Methods: In this retrospective observational study, total 60 oocyte donation cycles were included (38 were fresh and 22 were vitrified oocytes cycle, respectively). After a thorough screening, controlled ovarian hyperstimulation for donors was performed using flexible antagonist protocol. All mature oocytes were allocated into “vitrified oocytes” and “fresh oocytes” groups. Vitrification technique using Cryotop method was used for oocyte freezing. Both clinical and laboratory outcomes of vitrified and fresh oocytes in donor cycles were compared.

Results: A total of 600 oocytes (226 “vitrified oocytes” and 374 fresh oocytes), were studied. After warming 218 oocytes survived resulting in survival rate of 96.4%. Fertilization rate and embryo formation rate was 86.2% and 93.6%, respectively. Results of frozen-thawed oocyte donor cycles were compared with fresh donation cycles. For fresh oocyte group, fertilization rate and embryo formation rate was 83.4% and 92.6%, respectively. On comparing clinical outcomes, clinical pregnancy rate was 60.5% in fresh group and 63.6% in vitrified group.

Conclusions: Both clinical and laboratory results obtained in the study suggest that oocyte cryopreservation can be performed with reproducible success, thus vitrification technique can be provided as a useful tool for achieving highly successful outcomes in an oocyte donor program.

Fertility Preservation for Pediatric and Adolescent Patients With Cancer: Medical and Ethical Considerations

Many cancers presenting in children and adolescents are curable with surgery, chemotherapy, and/or radiotherapy. Potential adverse consequences of treatment include sterility, infertility, or subfertility as a result of gonad removal, damage to germ cells as a result of adjuvant therapy, or damage to the pituitary and hypothalamus or uterus as a result of irradiation. In recent years, treatment of solid tumors and hematologic malignancies has been modified in an attempt to reduce damage to the gonadal axis. Simultaneously, advances in assisted reproductive technology have led to new possibilities for the prevention and treatment of infertility. This clinical report reviews the medical aspects and ethical considerations that arise when considering fertility preservation in pediatric and adolescent patients with cancer.

Chemotherapy Associated Ovarian Failure

As the incidence of malignancies in young adults is increasing, fertility preservation in cancer survivors arises as a major concern. Especially among female cancer patients, pregnancy rates are estimated to be 40% lower compared to women of the same age. Nowadays oncologists are to be preoccupied not only with their patients' successful treatment, but also with the maintenance of the potential of the latter to conceive and obtain children. Chemotherapy associated ovarian failure (COF), refers to disruption of ovarian function both as an endocrine gland and as a reproductive organ, due to previous exposure to chemotherapy agents. Although the underlying mechanism is not fully understood, it is supposed that chemotherapy agents may induce either DNA damage of premature ovarian follicle or early activation and apoptosis of them, resulting into early exhaustion of available follicle deposit. Various chemotherapy agents have been associated with COF with the highest incidence being reported for patients undergoing combination regimens. Although a variety of alternatives in order to maintain ovarian function and fertility in female cancer survivors are available, adequately established practices to do so are lacking. Thus, it is of major importance to investigate further and collect sufficient evidence, aiming to guide patients and physicians in everyday clinical practice.

Fertility Counseling and Preservation for Breast Cancer Patients

Fertility preservation includes all the necessary steps that have to be taken in order to implement a woman's aim for preserving and enhancing her future chances of having her own biological offspring.There are two available choices for patients to maintain their fertility.The first category includes all the preventive methods following the principle of reduction of gonadotoxicity, in terms of using fewer toxic drugs to the ovaries and similarly milder radiation regimens. It also includes the administration of agents that would keep the ovaries suppressed, to minimize the harmful effects of systemic therapy on the oocytes.The second includes necessary artificial reproductive technology procedures for collecting and freezing either gametes (oocytes) or zygotes (embryos). This can be accomplished with immature oocyte pickup followed by in vitro maturation (IVM). Alternatively, mature oocytes can be collected after minimal ovarian stimulation with very small doses or no medication at all, or through a natural cycle.Beyond that, promising is the modern option of ovarian tissue cryopreservation for future transplantation, while the option of oocyte donation is actually an option for childbearing, not for fertility.

ANZSREI consensus statement on elective oocyte cryopreservation

BACKGROUND

One in six Australian women and couples suffer infertility. A rising proportion relates to advanced maternal age, associated with poorer oocyte quality and in vitro fertilisation (IVF) outcomes. Internationally, oocyte cryopreservation technology applied to oocytes vitrified before 35 years provides similar live-birth statistics compared to IVF treatment using fresh oocytes. Oocyte cryopreservation is accessible in Australasian settings and elective uptake is increasing. For women accessing treatment, oocyte cryopreservation may expand future family building options.

AIMS

To develop the first Australasian Certification in Reproductive Endocrinology and Infertility (CREI) subspecialist-led consensus guideline on oocyte cryopreservation.

METHODS

The ANZSREI ACCEPT (Australasian CREI Consensus Expert Panel on Trial evidence group) met in 2017 and 2018 and identified clinical aspects of care for inclusion and review. Review of the available evidence was conducted and consensus statements prepared. Areas of dissent of expert opinion and for further research were noted.

RESULTS

Consensus was reached on definition and best practice in oocyte cryopreservation for freeze method, controlled ovarian stimulation, medical risk reduction and treatment and outcomes counselling. The term 'social egg freezing' may marginalise, stigmatise or attribute social blame to women, and there is a need to revise this to a neutral and non-judgemental term such as elective or planned oocyte cryopreservation.

CONCLUSION

Oocyte cryopreservation has the potential to improve cumulative live birth outcomes for women. Implementation of this guideline should facilitate an optimal approach for providing care.

Dynactin pathway-related gene expression is altered by aging, but not by vitrification

The storage of surplus oocytes by cryopreservation (OC) is a widely used tool in assisted reproductive technology, but there is a great debate about the effects of cryopreservation on oocyte competence. It is known that OC may affect meiotic spindles but remains unclear if OC may increase the risk of aneuploidy. The aim of this study was to test the effects of OC and women aging on the expression of cytokinesis-related genes playing an important role in the segregation of chromosomes (DCTN1, DCTN2, DCTN3, DCTN6 and PLK1). Results highlighted that OC do not modify the expression of the selected genes, whereas women aging modulate the expression of all transcripts, confirming that aging is the crucial factor affecting meiosis and aneuploidy risk. A new role for Dynactin and PLK1 was shed in light, providing information on the ageing process in the oocyte which may be associated to reduced fertility.

Recent Advances in Fertility Preservation and Counseling for Reproductive-Aged Women with Colorectal Cancer: A Systematic Review

BACKGROUND

The incidence of colorectal cancer among reproductive-aged women is increasing. Concerns regarding future fertility are secondary only to concerns regarding survival and may significantly impact quality of life among reproductive-aged female cancer survivors. Fertility preservation counseling reduces long-term regret and dissatisfaction among cancer survivors. Health care providers counseling patients with colorectal cancer must understand the impact of cancer treatment on future reproductive potential.

OBJECTIVE

This review aims to examine the effects that colorectal cancer treatments have on female fertility and summarize existing and emerging options for fertility preservation.

DATA SOURCES

EMBASE, National Library of Medicine (MEDLINE)/PubMed, Cochrane Review Library were the data sources for this review.

STUDY SELECTION

A systematic literature review was performed using exploded MeSH terms to identify articles examining the effect of surgery, chemotherapy, and radiation, as well as fertility preservation options for colorectal cancer on female fertility. Relevant studies were included.

MAIN OUTCOME MEASURES

The primary outcome was the effect of colorectal cancer treatment on fertility.

RESULTS

There are limited data regarding the impact of colorectal surgery on fertility. The gonadotoxic effects of chemotherapy on reproductive capacity depend on age at the time of chemotherapy administration, cumulative chemotherapy, radiation dose, type of agent, and baseline fertility status. Chemotherapy-induced risks for colorectal cancers are considered low to moderate, whereas pelvic radiation with a dose of 45 to 50 Gray induces premature menopause in greater than 90% of patients. Ovarian transposition may reduce but not eliminate the damaging effect of radiation on the ovaries. Embryo and oocyte cryopreservation are considered standard of care for women desiring fertility preservation, with oocyte cryopreservation no longer being considered experimental. Ovarian tissue cryopreservation remains experimental but may be an option for select patients. The use of gonadotropin-releasing hormone agonists remains controversial and has not been definitively shown to preserve fertility.

LIMITATIONS

The limitations of this review are the lack of randomized controlled trials and high-quality studies, as well as the small sample sizes and the use of surrogate fertility markers.

CONCLUSION

Reproductive-aged women with colorectal cancer benefit from fertility preservation counseling before the initiation of cancer treatment.

For whom the egg thaws: insights from an analysis of 10 years of frozen egg thaw data from two UK clinics, 2008-2017

PURPOSE

To better understand the characteristics of patients who returned to thaw their frozen eggs to attempt conception and their outcomes.

METHODS

A retrospective analysis of clinical records for all own egg thaw patients in two UK fertility clinics across 10 years, 2008-2017.

RESULTS

There were 129 patients who returned to thaw their eggs, of which 46 had originally frozen their eggs for social reasons and 83 for a variety of clinical, incidental, and ethical reasons (which we have called "non-social"). Women who had frozen their eggs for social reasons were single at time of freeze, with an average age of 37.7. They kept their eggs in storage for just under 5 years, returning to use them at the average age of 42.5. 43.5% were single at time of thaw, and 47.8% used donor sperm to fertilise their eggs. Women whose eggs were frozen for non-social reasons were almost all (97.6%) in a relationship at both time of freeze and thaw. They had an average age of 37.2 at first freeze and 37.6 at thaw, having kept their eggs in storage for an average of 0.4 years. Overall, there was a 20.9% success rate among women attempting conception with frozen-thawed eggs.

CONCLUSIONS

Despite widespread assumptions, many women attempting conception with thawed eggs had not initially frozen them for social reasons. Women who froze their eggs for social reasons presented distinctly and statistically different characteristics at both time of freeze and thaw to women whose eggs were frozen for non-social reasons.

Spindle and chromosome configuration analysis of human biopsied versus non-biopsied embryos by confocal laser scanning microscopy following vitrification

SummaryThe aim of this study was to investigate the effects of zona drilling and biopsy on day 3 followed by vitrification on day 5 on the cytoskeleton and development of human embryos, by analysing survival rates and spindle and chromosome configurations by fluorescence and confocal laser scanning microscopy in human biopsied and non-biopsied embryos. In total, 98 human blastocysts (50 non-biopsied and 48 following biopsy on day 3) were vitrified on day 5 using either a commercial dimethyl sulphoxide (DMSO)-free vitrification kit or increasing concentrations of DMSO/EG (5%/5-10%/10-20%/20%). Following warming, the blastocysts were allowed to recover in culture for 24 h and were immunostained with α-tubulin, acetylated tubulin, and/or γ-tubulin antibodies in combination with 4',6-diamidino-2-phenylindole (DAPI). Labelled embryos were examined by both fluorescence and confocal laser scanning microscopy. The survival rates following warming (92% non-biopsied vs 83.3% biopsied) and the incidence of normal spindle chromosome configurations was not statistically different between the two groups (65.2% non-biopsied vs 59.2% biopsied, P&gt;0.05). The incidence of spindle abnormalities including multipolarity, chromosome lagging, congression failure and chromosome bridging were also similar between the two groups (P&gt;0.05). This study is the first to compare the incidence of cytoskeletal abnormalities in biopsied and non-biopsied human embryos following vitrification. We conclude that there was no significant difference in the survival rates and the incidence of spindle abnormalities between the two groups.

A brief history of oocyte cryopreservation: Arguments and facts

The term "cryopreservation" refers to the process of cooling cells and tissues and storing them at subzero temperatures in order to stop all biological activity and preserve their viability and physiological competences for future use. Cooling to subzero temperatures is not a physiological condition for human cells; this is probably due to the high content of water in the living matter, whose conversion to ice crystals may be associated with severe and irreversible damage. Among reproductive cells and tissues, metaphase II oocytes are notably vulnerable to cryopreservation, mainly because of their large size, low surface area to volume ratio, relatively high water content and presence of the meiotic spindle. As human biological systems lack efficient internal defense mechanisms against chilling injuries, it is of the utmost importance to supply adequate external support, in terms of cryoprotectant additives, appropriate cooling/warming rates, and suitable long-term storage. Over the years, scientists have proposed different cryopreservation strategies in the effort to achieve an optimized recipe ensuring cell survival and, at the same time, maintenance of the physiological functions and abilities necessary to continue life. However, despite the first success obtained in the 1980s with frozen oocytes, it was not until recently that notable improvements in the cryopreservation technique, thanks to the advent of vitrification, allowed a breakthrough of this fine procedure.

Human oocyte morphometry before and after cryopreservation: A prospective cohort study

The cryopreservation of human oocytes is an important strategy to spare fertility in women submitted to gonadotoxic therapy, ovarian surgery, or even to allow gestation by assisted reproduction technology after natural ovarian senescence. Methods to predict oocyte resistance to cryopreservation are still based on qualitative morphological assessment. In this study we evaluated whether morphometric characteristics of mature oocytes before vitrification and after warming are related to successful fertilization by intracytoplasmic sperm injection (ICSI). This was a prospective cohort study including 28 infertile women and 71 oocytes. Morphometric assessments included oocyte diameter, perivitelline space (PS), zona pellucida (ZP) and first polar body (PB). Out of 49 warmed oocytes, 27 (55%) survived cryopreservation and their pre-vitrification measures were similar to those of the 22 oocytes that perished. However, the oocytes that eventually failed to be fertilized had undergone more enlargement of the total diameter (p = 0.029) and shrinking of the PS (p = 0.033) after cryopreservation, compared to oocytes that were successfully fertilized. These findings suggest that the morphometric characteristics of fresh oocytes do not predict their survival to vitrification, while fertilization failure is associated with oocyte enlargement and PS shrinking after cryopreservation.

Elective egg freezing without medical indications

The aim of this review is to provide current knowledge on fertility preservation for non-medical reasons in women willing to postpone childbearing. The topic is highly debatable, starting from disagreement about its terminology, the number of eggs necessary to predict chances of success, and the safety and socio/ethical point of view. Cost analysis and discrepancies among countries' recommendations and regulations are described to confirm the controversies and unsolved issues around this very interesting topic. Finally, an overview on the returning rate of women among "egg bankers" and reasons behind their decisions are illustrated.

Caffeine and oocyte vitrification: Sheep as an animal model

Oocyte cryopreservation is valuable way of preserving the female germ line. Vitrification of immature ovine oocytes decreased the levels of both maturation promoting factor (MPF) and mitogen-activated protein kinase (MAPK) in metaphase II (MII) oocytes after IVM. Our aims were 1) to evaluate the effects of vitrification of ovine GV-oocytes on spindle assembly, MPF/MAP kinases activities, and preimplantation development following IVM and IVF, 2) to elucidate the impact of caffeine supplementation during IVM on the quality and development of vitrified/warmed ovine GV-oocytes. Cumulus-oocyte complexes (COCs) from mature ewes were divided into vitrified, toxicity and control groups. Oocytes from each group were matured in vitro for 18 h in caffeine free IVM medium and denuded oocytes were incubated in maturation medium supplemented with 10 mM (+) or without (−) caffeine for another 6 h. At 24 h.p.m., oocytes were evaluated for spindle configuration, MPF/MAP kinases activities or fertilized and cultured in vitro for 7 days. Caffeine supplementation did not significantly affect the percentages of oocytes with normal spindle assembly in all the groups. Caffeine supplementation during IVM did not increase the activities of both kinases in vitrified groups. Cleavage and blastocyst development were significantly lower in vitrified groups than in control. Caffeine supplementation during the last 6 h of IVM did not significantly improve the cleavage and blastocyst rates in vitrified group. In conclusion, caffeine treatment during in vitro maturation has no positive impact on the quality and development of vitrified/warmed ovine GV-oocytes after IVM/IVF and embryo culture.

Recent advances in oncofertility care worldwide and in Japan

BACKGROUND

Oncofertility is a crucial facet of cancer supportive care. The publication of guidelines for the cryopreservation of oocytes and ovarian tissue is becoming increasingly prevalent in Japan and an updated overview is necessary.

METHODS

In order to provide an updated overview of oncofertility care, original research and review articles were searched from the PubMed database and compared in order to present clinical care in Japan.

RESULTS

In Western countries, various methods for ovarian stimulation, such as the combined use of aromatase inhibitors and random-start protocols, have been reported. Although ovarian tissue cryopreservation, mainly performed via the slow-freezing method, also has yielded >100 live births, the optimal indications and procedures for the auto-transplantation of cryopreserved tissue have been under investigation. In Japan, however, vitrification is prevalent for ovarian tissue cryopreservation, although its efficacy has not yet been established. The quality of network systems for providing oncofertility care in Japan varies greatly, based on the region.

CONCLUSION

There remain many issues in the optimization of oncofertility care in Japan. Along with the regional oncofertility networks, the creation of "oncofertility navigators" from healthcare providers who are familiar with oncofertility, such as nurses, psychologists, and embryologists, could be useful for supplementing oncofertility care coordination, overcoming the issues in individual regions.

Fertility Issues in Pediatric Urology

Improved understanding of the pathogenesis and natural history of many urologic disorders, as well as advances in fertility preservation techniques, has increased the awareness of and options for management of fertility threats in pediatric patients. In children, fertility may be altered by oncologic conditions, by differences in sexual differentiation, by gonadotoxic drugs and other side effects of treatment for nonurologic disorders, and by urologic conditions, such as varicocele and cryptorchidism. Although fertility concerns are best addressed in a multidisciplinary setting, pediatric urologists should be aware of the underlying pathophysiology and management options to properly counsel and advocate for patients.

Reproductive aging and elective fertility preservation

Reproductive aging is a natural process that occurs in all women, eventually leading to reproductive senescence and menopause. Over the past half century there has been a trend towards delayed motherhood. Postponing reproduction can increase the chance of a woman remaining involuntarily childless as well as an increase in pregnancy complications in those that do achieve pregnancy at advanced maternal age. Despite the well-documented decrease in fecundity that occurs as a woman ages, reproductive aged women frequently overestimate the age at which a significant decline in fertility occurs and overestimate the success of assisted reproductive technologies (ART) to circumvent infertility. Oocyte cryopreservation enables women to achieve genetically related offspring in the event that they desire to postpone their childbearing to an age after which a significant decline in fertility occurs or in circumstances in which their reproductive potential is compromised due to medical pathology. Available success rates and safety data following oocyte cryopreservation have been reassuring and is not considered experimental according to the American Society for Reproductive Medicine and the European Society for Human Reproduction and Embryology. This review article will focus on an evidence-based discussion relating to reproductive aging and oocyte cryopreservation.

Counseling patients on reproductive aging and elective fertility preservation-a survey of obstetricians and gynecologists' experience, approach, and knowledge

PURPOSE

What are the experience, approach, and knowledge of US Obstetricians and Gynecologists' (ob-gyn) towards counseling patients on reproductive aging (RA) and elective fertility preservation (EFP).

METHODS

A cross-sectional survey emailed by the American College of Obstetricians and Gynecologists (ACOG) to 5000 ACOG fellows consisting of 9 demographic and 28 questions relating to counseling patients on RA and EFP.

RESULTS

Seven hundred and eighty-four responders completed the survey. Although 82.8% agreed that conversations relating to RA should take place with patients desiring future childbearing and delaying due to social reasons, only 27.6% stated that they frequently counsel these women aged 18-34 years old, compared to 75.8% aged 35-44 years old (P < 0.01). Limited time (75.8%) and limited knowledge (41.4%) were amongst the most frequent reported barriers towards counseling patients on RA. Fifty-eight percent stated that they have been asked about EFP by patients. Although 74.8% agreed that conversations should take place related to EFP in women desiring future childbearing and delaying due to social reasons, only 27.6% stated that they frequently counsel these patients on EFP (P < 0.01). Limited time (75%) and limited knowledge (59.9%) were amongst the most frequent barriers towards counseling on EFP.

CONCLUSIONS

In the USA, methods to improve patient counseling and provider knowledge on RA and EFP are warranted and further studies are needed to address optimal methods to improve counseling and knowledge related to these topics.

Minimum volume Spatula MVD vitrification method improves embryo survival compared to traditional slow freezing, both for in vivo and in vitro produced mice embryos

This study was conducted to compare the effect of minimum volume Spatula MVD vitrification (VIT) versus traditional slow freezing (SLF) of mouse embryos. A total of 2,617 8-cell in vivo derived and 2-cell in vitro produced B6D2 mouse embryos were subjected to freezing/thawing or vitrification/warming, while fresh embryos were used as control group. Embryo recovery, survival and development rate, pregnancy rate and offspring production were analyzed. In Experiment 1, 8-cell in vivo derived embryos were subjected to in vitro culture, resulting in greater survival and development rates at 3.5 days post coitum stage in VIT than in SLF group (P < 0.05). Although both methods reached an acceptable hatching rate (41.0% and 49.7% for VIT and SLF, respectively; P=NS), it was significantly lower respect to the control group (67.8%, P < 0.01). In Experiment 2, 2-cell in vitro produced mouse embryos showed a similar recovery rate from the device after freezing/thawing or vitrification/warming (∼84%), however survival rate was significantly higher for vitrified/warmed (94.7%) than frozen/thawed embryos (85.1%; P < 0.01). Vitrified/warmed and control fresh embryos were transferred to surrogate mothers, revealing no differences both in pregnancy and offspring production rates. Our data demonstrate that minimum volume Spatula MVD method is a simple home-made useful technique for vitrification of 2-cell and 8-cell mouse embryos produced either in vitro or in vivo.

Female fertility preservation: past, present and future

Anti-cancer therapy, particularly chemotherapy, damages ovarian follicles and promotes ovarian failure. The only pharmacological means for protecting the ovaries from chemotherapy-induced injury is gonadotrophin-releasing hormone agonist, but its efficiency remains controversial; ovarian transposition is used to shield the ovary from radiation when indicated. Until the late 1990s, the only option for fertility preservation and restoration in women with cancer was embryo cryopreservation. The development of other assisted reproductive technologies such as mature oocyte cryopreservation andin vitromaturation of oocytes has contributed to fertility preservation. Treatment regimens to obtain mature oocytes/embryos have been modified to overcome various limitations of conventional ovarian stimulation protocols. In the last decades, several centres have begun cryopreserving ovarian samples containing primordial follicles from young patients before anti-cancer therapy. The first live birth following implantation of cryopreserved-thawed ovarian tissue was reported in 2004; since then, the number has risen to more than 130. Nowadays, ovarian tissue cryopreservation can be combined within vitromaturation and vitrification of oocytes. The use of cryopreserved oocytes eliminates the risk posed by ovarian implantation of reseeding the cancer. Novel methods for enhancing follicular survival after implantation are presently being studied. In addition, researchers are currently investigating agents for ovarian protection. It is expected that the risk of reimplantation of malignant cells with ovarian grafts will be overcome with the putative development of an artificial ovary and an efficient follicle class- and species-dependentin vitrosystem for culturing primordial follicles.

Effects of cyclophosphamide administration on the in vitro fertilization of mice

PURPOSE

To evaluate the oocyte fertilization ability and embryo growth after cyclophosphamide (CPA) treatment in mice.

METHODS

Mice were treated with CPA at different doses (0-800 mg/kg body weight). The oocytes then were retrieved and evaluated for their in vitro fertilization efficiency.

RESULTS

The average number of metaphase II (MII) oocytes significantly decreased by ≥400 mg/kg CPA administration. The fertilization rate also decreased in the group that was treated with ≥400 mg/kg CPA. However, after fertilization, the embryos demonstrated normal growth ability. Two weeks after CPA administration, the number of mice from which the oocytes could be retrieved markedly decreased, but the fertilization rate and development of morphological features in the embryos were similar to those of the controls. One month after CPA administration, the number of mice from which the oocytes could be retrieved, fertilization rate, and development of the morphological features in the embryos were similar to those of the controls.

CONCLUSION

The number of oocytes decreased as the CPA administration level increased; however, the oocytes' potential for fertilization and development to the blastocyst stage was not significantly affected. One month after CPA administration, the number of oocytes and the potential for development into blastocysts were recovered.

Fertility preservation in pediatric and young adult female cancer patients

As the 5-year survival rate increases up to 80% in pediatric cancer patients, the number of women patients with reduced gonadal function by chemotherapy and radiotherapy increases. The gonadal toxicity of pediatric patients varies highly according to the chemotherapeutic agent and the type of radiotherapy. Although American Society of Clinical Oncology published the guideline for fertility preservation, additional scientific and ethical concerns should be considered for clinical practice. In addition, only the experimental method can be applied for the prepubertal patients in contrast to the postpubertal patients. In this review, we will discuss some options for preserving fertility among women's quality of life issues.

Ovarian reserve and response to stimulation in women undergoing fertility preservation according to malignancy type

RESEARCH QUESTION

Does ovarian reserve and ovarian response to ovarian stimulation in women with cancer undergoing oocyte vitrification for fertility preservation vary according to the type of malignancy?

DESIGN

Retrospective cohort study including 105 women aged between 18 and 40 years, who were referred for fertility preservation (oocyte vitrification) between 2013 and 2016. The women were divided into three groups: breast cancer, lymphoma or other cancer. All of them had been recently diagnosed with cancer, with gonadotoxic treatment scheduled, and had oocyte vitrification after ovarian stimulation with antagonist protocol.

RESULTS

Baseline antral follicle count and anti-Müllerian hormone were no different between women with breast cancer, lymphoma or other cancer. The number of cancelled cycles for poor ovarian response was similar between the groups. The number of FSH units per mature oocyte, the number of mature oocytes (metaphase II) retrieved, and the oocyte maturity rate were not significantly different between the three groups.

CONCLUSIONS

As the type of cancer does not seem to significantly affect ovarian reserve and ovarian response to ovarian stimulation, our results do not support the relevance of integrating this parameter when establishing ovarian stimulation protocol for oocyte vitrification cycle in women with cancer.

Clinical outcomes of a vitrified donor oocyte programme: A single UK centre experience

OBJECTIVE

To assess the survival rate of vitrified oocytes used in an egg recipient programme and compare the clinical outcomes of pregnancy and live-birth rates per warmed oocyte with fresh autologous oocytes. The differences in the obstetrical outcomes between the two groups were also studied.

DESIGN

A prospective case control study from a single in-vitro fertilisaton (IVF) Centre in UK SETTING: Centre of Reproductive and Genetic Health (CRGH), London POPULATION: Vitrified oocytes from egg donors and autologous fresh oocytes from patients attending for an IVF cycle METHODS: The study group consisted of 1490 vitrified oocytes, which were obtained from 145 egg donors who underwent a stimulation cycle at CRGH Centre. The control group included 145 age-matched women who underwent intra cytoplasmic sperm injection (ICSI) treatment with their own oocytes (n = 1528). The clinical outcomes clinical pregnancy rates (CPR) and live-birth rates (LBR) and obstetrical outcomes (gestational age and weight at delivery) were compared between the two groups. Statistical analysis of the summary data and logistic regression analysis was performed using statistical packages (SPSS Version 23 and Stata 2015). The percentages of all parameters in the cases and control groups were compared by Fisher's exact test. A statistical significance level of 5% was adopted throughout the study.

MAIN OUTCOME MEASURES

Survival rate per thawed oocyte, clinical pregnancy rate and live-birth rate per embryo transfer was compared to the autologous oocyte group RESULTS: The survival rate of vitrified oocytes was 73.6% (95% CI: 71.3-75.8%). The clinical pregnancy rate (per embryo transfer) using vitrified oocytes was found to be 51.8% compared to 59.3% in the control group. The live birth rate per embryo transfer in the vitrified oocyte group was 46% (95% CI 37.4-54.7%) compared to 57.1% (95% CI 48.5-68.5%) in the control group. The live-birth rate per thawed oocyte was found to be 4.2%. The gestational ages of the fetus at delivery in both the groups were comparable 39.0 (95% CI 32.7-41.9%) and 39.1 (95% CI 25.6-42.0) (p = 0.38). There was no statistically significant difference in the birth weight between the study and the control group 3100 g (750-4337) and 3232 g (1616-4500) respectively (p = 0.28).

CONCLUSIONS

This is the first study reporting on the efficacy of a vitrified donor oocyte programme from within the UK. There were no significant differences in the obstetrical outcomes between vitrified donor oocytes and autologous oocytes. The above data will be encouraging for women who are undertaking egg freezing for medical and or social reasons.

[Endometriosis and fertility preservation: CNGOF-HAS Endometriosis Guidelines]

Fertility preservation (FP) techniques are progressing rapidly these past few years thanks to the oocyte vitrification. Indication of FP techniques is now extended to non-oncological situation that may induce risk of premature ovarian failure. Ovarian endometriosis can lead to premature ovarian failure and further infertility due to the high risk of ovarian cysts recurrence and surgery. To date, there is no cohort study regarding FP and endometriosis as well as no recommendation. Our purpose is to review the arguments in favor of FP in this specific area and to elaborate strategies according to each clinical form.

Outcome of Oocyte Vitrification Combined with Microdissection Testicular Sperm Extraction and Aspiration for Assisted Reproduction in Men

Background

As a safety and efficacy protocol, oocyte vitrification has been widely used in IVF treatment. The aim of this study was to evaluate the outcome of ICSI-ET utilizing vitrified oocytes with sperm obtained from non-obstructive azoospermia (NOA) patients via micro-TESE.

Material/Methods

A total of 150 NOA patients underwent micro-TESE. Ten patients were unable to ejaculate and refused to accept TESA at the time of oocyte retrieval; later, these patients underwent TESA. A total of 174 obstructive azoospermia (OA) patients underwent TESA. Vitrified oocytes were used with micro-TESE in 35 cycles (group 1), and TESA in 10 cycles (group 2). Fresh oocytes were used with micro-TESE in 38 cycles (group 3) and TESA in 174 cycles (group 4).

Results

The overall sperm retrieval rate of the 150 NOA patients was 48.7% (73/150). A total of 257 cycles of ICSI-ET were conducted with testicular spermatozoa; 212 cycles utilized fresh oocytes and 45 cycles utilized vitrified oocytes. No differences were observed with fertilization (73.8%, 77.2%,72.8%, 73.6%), implantation (33.3%, 34.7%, 33.8%, 37.5%), or clinical pregnancy rates (51.4%, 60%, 52.6%, 51.7%) for groups 1 through 4, respectively (P>0.05). Developmental competence was greatest among couples using sperm obtained via TESA rather than micro-TESE, not dependent on whether vitrified or fresh oocytes were utilized. Fertilization, implantation, and clinical pregnancy rates did not differ between using fresh vs. vitrified oocytes, nor did they differ between using testicular sperm derived from men with NOA vs. men with OA.

Conclusions

Vitrified oocytes combined with micro-TESE showed similar clinical efficacy when compared with fresh oocytes.

Is egg freezing a good response to socioeconomic and cultural factors that lead women to postpone motherhood?

In western societies, a growing number of women are currently turning to social egg freezing, a technique that makes it possible to freeze oocytes and thus preserve female reproductive possibilities. The current ethical debate has focused on normative aspects concerning the question of whether social egg freezing empowers women's reproductive autonomy. Due to this narrow focus on autonomy, deeper questions concerning the socio-economic conditions and cultural factors that lead women to delay reproduction, to feel pressured by their biological clock, and thus to consider social egg freezing have not yet received sufficient attention and analysis. The aim of this study was to broaden the ethical debate by focusing on whether social egg freezing is a good response to the socioeconomic and cultural constraints that lead women to postpone motherhood, and therefore whether it can be seen as a means of achieving what in virtue ethics is known as a 'good life'. I will argue that while social egg freezing can be seen as a means to empower women to adapt to current socioeconomic constraints, it is not an adequate response to cultural factors, as these cannot be solved by simply extending a woman's fertility.

Oocyte vitrification for elective fertility preservation: the past, present, and future

PURPOSE OF REVIEW

Oocyte cryopreservation is no longer experimental and one of its rapidly growing indications is elective fertility preservation. Currently there is no sufficient evidence to support its practice and therefore its place in IVF remains uncertain.

RECENT FINDINGS

Vitrification has superior post-thaw survival and fertilization outcomes compared with oocytes that were frozen with the slow-freeze technique. Oocyte vitrification produces similar IVF outcomes compared with fresh oocytes and is not associated with further obstetrical or perinatal morbidity. Undergoing elective oocyte cryopreservation between ages 35 and 37 will optimize live birth rates as well as cost effectiveness from mathematical models.

SUMMARY

In women who delay child bearing, elective oocyte cryopreservation in the mid 30s may be beneficial in terms of live birth rates and cost effectiveness. Prospective studies of women who have undergone oocyte cryopreservation and are now attempting conception are needed before official recommendations can be made regarding elective egg freezing.

No. 356-Egg Freezing for Age-Related Fertility Decline

OBJECTIVE

To provide a comprehensive review and evidence based recommendations for Canadian fertility centres that offer social egg freezing.

OUTCOMES

In social egg freezing cycles we evaluated thawed oocyte survival rates, fertilization rates, embryo quality, pregnancy rates, and live birth rates. We also review how these outcomes are impacted by age, ovarian reserve, and the number of eggs cryopreserved. Finally, we discuss the risks of social egg freezing, the alternatives, the critical elements for counselling and informed consent, and future reporting of egg freezing outcome data.

EVIDENCE

Published literature was reviewed through searches of MEDLINE and CINAHL using appropriate vocabulary and using key words ("oocyte cryopreservation," "egg freezing," "egg vitrification," "social egg freezing," and "elective egg freezing"). Results included systematic reviews, randomized controlled trials, controlled clinical trials, and observational studies. Expert opinion based on clinical experience, descriptive studies, or reports of expert committees was also included to discuss aspects of egg freezing not currently rigorously studied.

VALUES

The evidence obtained was reviewed and evaluated by the Clinical Practice Guideline (CPG) Committees of the Canadian Fertility and Andrology Society (CFAS) under the leadership of the principal authors.

BENEFITS, HARMS, AND COSTS

Implementation of this guideline should assist the clinician to develop an optimal approach in providing counselling for egg freezing while minimizing harm and improving patient outcomes during treatment.

VALIDATION

These guidelines have been reviewed and approved by the membership of the CFAS and by the CPG Committees of CFAS and The Society of Obstetricians and Gynaecologists of Canada (SOGC).

SPONSORS

CFAS and SOGC.

RECOMMENDATIONS

Fertility Preservation in Breast Cancer

As more young women survive breast cancer, fertility preservation (FP) is an important component of care. This review highlights the importance of early pretreatment referral, reviews the risks of infertility associated with breast cancer treatment, and defines existing and emerging techniques for FP. The techniques reviewed include ovarian suppression, embryo cryopreservation, oocyte cryopreservation, and ovarian tissue cryopreservation and transplantation. The barriers women face, such as not being appropriately referred and the costs of treatment, also are addressed. Multidisciplinary, patient-centered care is essential to discussing FP with patients with breast cancer and ensuring appropriate care that includes quality of life in survivorship.

Egg donation of vitrified oocytes bank produces similar pregnancy rates by blastocyst transfer when compared to fresh cycle

PURPOSE

Advances in reproductive techniques, mainly the introduction of oocyte vitrification, have provided the opportunity to conceive from oocyte banks. The aim of this study was to compare the clinical outcomes of fresh and vitrified oocytes in an egg donation program following blastocyst transfer.

METHODS

This retrospective observational study included 504 oocyte donation cycles. All donor women were younger than 30 years of age. The recipient cycles were divided into two groups: fresh oocytes (n = 78) or vitrified oocytes (n = 426). All oocytes were fertilized by ICSI using ejaculated sperm, followed by blastocyst transfer. Endometrium preparation was performed with estradiol valerate plus micronized progesterone according to standard protocols.

RESULTS

Recipients were of similar age (fresh 42.0 ± 4.5 years vs vitrified 41.8 ± 4.8 years; p = 0.790). The fresh group received more mature oocytes for injection compared to the vitrified group (10.1 ± 2.8 vs 9.2 ± 2.2; p = 0.005). The two pronuclei (2PN) rate (74.5 vs 77.4%; p = 0.195) and blastocyst rate (48.8 vs 51.6%; 0.329) were similar between the fresh and vitrified groups, respectively. The rates of clinical pregnancy were 60.9% in the fresh and 59.0% in the vitrified groups (p = 0.771).

CONCLUSIONS

Our findings suggest that vitrified oocytes result in similar pregnancy rates when compared to fresh oocytes with blastocyst transfer in an egg donation program. Moreover, vitrified oocytes may allow for a better cycle schedule, starting with a lower number of oocytes to be fertilized. Therefore, we hypothesize that egg banks with vitrified oocytes could be safely utilized in an egg donation program.