The added value of embryo cryopreservation to cumulative ongoing pregnancy rates per IVF treatment: is cryopreservation worth the effort?

Cryopreservation of embryos and oocytes in human assisted reproduction

Both sperm and embryo cryopreservation have become routine procedures in human assisted reproduction and oocyte cryopreservation is being introduced into clinical practice and is getting more and more widely used. Embryo cryopreservation has decreased the number of fresh embryo transfers and maximized the effectiveness of the IVF cycle. The data shows that women who had transfers of fresh and frozen embryos obtained 8% additional births by using their cryopreserved embryos. Oocyte cryopreservation offers more advantages compared to embryo freezing, such as fertility preservation in women at risk of losing fertility due to oncological treatment or chronic disease, egg donation, and postponing childbirth, and eliminates religious and/or other ethical, legal, and moral concerns of embryo freezing. In this review, the basic principles, methodology, and practical experiences as well as safety and other aspects concerning slow cooling and ultrarapid cooling (vitrification) of human embryos and oocytes are summarized.

NHS-funded IVF: consequences of NICE implementation

The UK National Institute for Health and Clinical Excellence (NICE) recommends that all subfertile women of < 40 years should be entitled to up to three IVF treatment cycles funded by the NHS. The full criteria have been implemented at The Newcastle Fertility Centre at Life since August 2009. The aim of this study was to evaluate the clinical outcome in terms of analysing the cumulative pregnancy rates. A retrospective analysis of data from 812 couples who started their first NHS-funded treatment after August 2009 was undertaken until there were 100 couples who had completed the three treatments. Cumulative pregnancy rates were calculated using life table analysis, and time intervals between treatments were recorded. The number of couples having first, second and third treatment cycles was 812, 298 and 100, respectively. The cumulative clinical pregnancy rates per each fresh cycle were 30.1%, 50.2% and 60.2%, and when frozen embryo transfers were included, they were 33.5%, 53.4% and 62.7%. The median + 2SD time interval between treatments was 11 and 10 months; 90.2% of the women were likely to complete up to three NHS-funded treatment cycles until they achieved a pregnancy. The NICE criteria offer most couples a chance of pregnancy, and the majority will take up the opportunity of undergoing three treatment cycles if required. The time interval between treatments indicated that it will take < 2 years for couples to complete the full course of NHS-funded treatment.

Cell lineage specific distribution of H3K27 trimethylation accumulation in an in vitro model for human implantation

Female mammals inactivate one of their two X-chromosomes to compensate for the difference in gene-dosage with males that have just one X-chromosome. X-chromosome inactivation is initiated by the expression of the non-coding RNA Xist, which coats the X-chromosome in cis and triggers gene silencing. In early mouse development the paternal X-chromosome is initially inactivated in all cells of cleavage stage embryos (imprinted X-inactivation) followed by reactivation of the inactivated paternal X-chromosome exclusively in the epiblast precursors of blastocysts, resulting temporarily in the presence of two active X-chromosomes in this specific lineage. Shortly thereafter, epiblast cells randomly inactivate either the maternal or the paternal X-chromosome. XCI is accompanied by the accumulation of histone 3 lysine 27 trimethylation (H3K27me3) marks on the condensed X-chromosome. It is still poorly understood how XCI is regulated during early human development. Here we have investigated lineage development and the distribution of H3K27me3 foci in human embryos derived from an in-vitro model for human implantation. In this system, embryos are co-cultured on decidualized endometrial stromal cells up to day 8, which allows the culture period to be extended for an additional two days. We demonstrate that after the co-culture period, the inner cell masses have relatively high cell numbers and that the GATA4-positive hypoblast lineage and OCT4-positive epiblast cell lineage in these embryos have segregated. H3K27me3 foci were observed in ∼25% of the trophectoderm cells and in ∼7.5% of the hypoblast cells, but not in epiblast cells. In contrast with day 8 embryos derived from the co-cultures, foci of H3K27me3 were not observed in embryos at day 5 of development derived from regular IVF-cultures. These findings indicate that the dynamics of H3K27me3 accumulation on the X-chromosome in human development is regulated in a lineage specific fashion.

Natural selection of human embryos: decidualizing endometrial stromal cells serve as sensors of embryo quality upon implantation

Background

Pregnancy is widely viewed as dependent upon an intimate dialogue, mediated by locally secreted factors between a developmentally competent embryo and a receptive endometrium. Reproductive success in humans is however limited, largely because of the high prevalence of chromosomally abnormal preimplantation embryos. Moreover, the transient period of endometrial receptivity in humans uniquely coincides with differentiation of endometrial stromal cells (ESCs) into highly specialized decidual cells, which in the absence of pregnancy invariably triggers menstruation. The role of cyclic decidualization of the endometrium in the implantation process and the nature of the decidual cytokines and growth factors that mediate the crosstalk with the embryo are unknown.

Methodology/Principal Findings

We employed a human co-culture model, consisting of decidualizing ESCs and single hatched blastocysts, to identify the soluble factors involved in implantation. Over the 3-day co-culture period, approximately 75% of embryos arrested whereas the remainder showed normal development. The levels of 14 implantation factors secreted by the stromal cells were determined by multiplex immunoassay. Surprisingly, the presence of a developing embryo had no significant effect on decidual secretions, apart from a modest reduction in IL-5 levels. In contrast, arresting embryos triggered a strong response, characterized by selective inhibition of IL-1β, -6, -10, -17, -18, eotaxin, and HB-EGF secretion. Co-cultures were repeated with undifferentiated ESCs but none of the secreted cytokines were affected by the presence of a developing or arresting embryo.

Conclusions

Human ESCs become biosensors of embryo quality upon differentiation into decidual cells. In view of the high incidence of gross chromosomal errors in human preimplantation embryos, cyclic decidualization followed by menstrual shedding may represent a mechanism of natural embryo selection that limits maternal investment in developmentally impaired pregnancies.

Calculating cumulative live-birth rates from linked cycles of assisted reproductive technology (ART): data from the Massachusetts SART CORS

OBJECTIVE

To determine the feasibility of linking assisted reproductive technology (ART) cycles for individual women to compare per-cycle and cumulative live-birth rates.

DESIGN

Historical cohort study.

SETTING

Clinic-based data.

PATIENT(S)

A total of 27,906 ART cycles with residency or treatment in Massachusetts during 2004-2006 and reported to the Society for Assisted Reproductive Technology Clinic Outcomes Reporting System (SART CORS) on-line database.

INTERVENTION(S)

None.

MAIN OUTCOME MEASURE(S)

Per-cycle and cumulative live-birth rates.

RESULT(S)

Linkage of cycles up to and including the first live-birth delivery revealed 14,265 women who averaged 1.9+/-1.2 SD cycles (range 1-11). These cycles yielded 9,452 pregnancies resulting in 7,675 live-birth deliveries. From cycle 1 to cycle 4, the cumulative live-birth rate for all patients increased from 30.4% to 43.3%, 49.1%, and 51.9%, respectively, and plateaued thereafter at about 53%. The cumulative live-birth rate after three cycles using donor oocytes was approximately 60% for women aged<43 years and >50% for women>or=43 years; for autologous oocytes it was 60.1% for ages<35 years and declined steadily to 8.5% for ages>or=43 years.

CONCLUSION(S)

The results demonstrate the feasibility of linking ART cycles for individual women from SART CORS to characterize cumulative live-birth rates.

Evidence-based clinical outcome of oocyte slow cooling

In the last few years, there has been a significant improvement in oocyte cryopreservation techniques. To investigate the clinical significance of oocyte freezing, an assessment of the cumulative pregnancy rate per started cycle derived from the use of fresh and frozen-thawed oocytes was performed. Between 2004 and 2006, 749 cycles were carried out, in which no more than three fresh oocytes were inseminated either by standard IVF or microinjection. Supernumerary mature oocytes were cryopreserved by slow cooling. Cryopreservation of fresh embryos was performed in rare cases to prevent the risk of ovarian hyperstimulation syndrome using a standard embryo freezing protocol. Fresh embryo transfer cycles totalled 680, 257 of which resulted in pregnancy. The pregnancy rates per patient and per transfer were 34.3% and 37.8% respectively. When frozen-thawed oocytes were used, following 660 thawing cycles, 590 embryo transfers were performed in 510 patients. Eighty-eight pregnancies were achieved with embryos from frozen oocytes, with a success rate of 17.2% per cycle. When fresh and frozen-thawed cycles were combined, the number of pregnancies was 355, giving a cumulative pregnancy rate of 47.4%. Oocyte cryopreservation can contribute considerably to the overall clinical success, ensuring a cumulative rate approaching that achievable with embryo storage.

FISH analysis of 15 chromosomes in human day 4 and 5 preimplantation embryos: the added value of extended aneuploidy detection

OBJECTIVE

Screening for an increased number of chromosomes may improve the detection of abnormal embryos and thus contribute to the capability of preimplantation genetic screening (PGS) to detect the embryo(s) for transfer in IVF with the best chance for a healthy child. Good-quality day 4 and 5 embryos were analyzed after cryopreservation for the nine chromosomes mostly recommended for screening (13, 14, 15, 16, 18, 21, 22, X and Y), next to six additional chromosomes which are less well studied in this context (1, 2, 7, 6, 10 and 17).

METHOD

The copy numbers of 15 chromosomes were investigated by fluorescence in situ hybridization (FISH) in three consecutive rounds. The proportion of aneuploid and mosaic embryos was determined and compared in retrospect to results in case only the recommended probe set had been analyzed.

RESULTS

A total of 52 embryos from 29 infertile women were analyzed. Screening the embryos for six additional chromosomes increased the proportion of abnormal embryos from 67 to 81% (P = 0.03), owing to an increase in mosaic embryos.

CONCLUSION

All but one of the meiotic aneuploidies found in this study would have been detected by the probe set most frequently used in PGS clinics. However, aneuploid cell lines originating from mitotic errors could be detected for almost all chromosomes, so screening of six additional chromosomes mainly increased the proportion of mosaic embryos. The added value of screening for six additional chromosomes in PGS for clinical practice will remain undetermined as long as the fate of mosaic embryos after transfer is unclear.

Cumulative pregnancy rates resulting from the use of fresh and frozen oocytes: 7 years' experience

Storing supernumerary embryos and transferring them later fully utilizes the reproductive potential of retrieved oocytes, allowing a significant increase in the overall number of pregnancies achieved from a single cycle of ovarian stimulation treatment. As an alternative to embryo cryopreservation, preservation of unfertilized oocytes has been proposed to maximize clinical outcome. This paper presents data concerning the cumulative pregnancy rate after use of fresh and cryopreserved oocytes. In 80 treatment cycles in which patients chose to have only a few fresh oocytes inseminated, 24 pregnancies were obtained (30.0%), with an implantation rate of 22.6%. After cryopreservation with the standard slow-cooling protocol, the survival, fertilization and cleavage rates of 918 frozen oocytes were 43.4, 51.5 and 86.0% respectively. A total of 14 frozen pregnancies were achieved, with pregnancy rate 19.2% per transfer and implantation rate 12.3%. The cumulative pregnancy rate was 47.5% per patient. Therefore, despite a low rate of oocyte post-thaw survival, it appears that oocyte storage appreciably improves the number of pregnancies per treatment cycle in cases in which only a minority of oocytes are destined for the fresh treatment. This outcome provides valuable information for appraising the chances of clinical success when the option of embryo cryopreservation is not available.

Oocytes in the empty follicle: a controversial syndrome

OBJECTIVE

To assess the prevalence and etiology of the empty follicle syndrome (EFS).

DESIGN

Observational longitudinal study.

SETTING

Tertiary fertility centers.

PATIENT(S)

All patients beginning in vitro fertilization (IVF) treatment from December 2002 to November 2004 were included. Couples undergoing IVF with donor oocytes or participating in an experimental IVF study were excluded from analysis.

INTERVENTION(S)

Identification of EFS cycles. Comparing ovarian hyperstimulation strategy, follicle count, and timing of human chorionic gonadotropin (hCG) for final oocyte maturation of the EFS cycles with normal IVF cycles.

MAIN OUTCOME MEASURE(S)

Number of follicles punctured, number of oocytes recovered, previous and future IVF attempts, and serum hormone levels.

RESULT(S)

Twenty-five of a total of 1,849 patients were identified with an EFS cycle. Reasons for occurrence of EFS cycles were mistiming of hCG for final oocyte maturation, premature ovulation, and poor ovarian response. None of the affected patients had experienced EFS cycles in earlier IVF attempts nor were there any recurrence in subsequent treatments.

CONCLUSION(S)

Accurate timing of induction of final oocyte maturation, properly scheduled ovarian hyperstimulation, instruction of patients and doctors, and full workup for IVF are essential for the successful recovery of oocytes. Occurrence of EFS in IVF can normally be attributed to a failure of at least one of these factors and probably rarely or never occurs otherwise.

Comparison of different treatment strategies in IVF with cumulative live birth over a given period of time as the primary end-point: methodological considerations on a randomized controlled non-inferiority trial

BACKGROUND

We discuss methodological considerations related to a study in IVF, which compares the effectiveness, health economics and patient discomfort of two treatment strategies that differ in both ovarian stimulation and embryo transfer policies.

METHODS

This was a randomized controlled clinical trial in two large Dutch IVF centres. The tested treatment strategies are: mild ovarian stimulation [including gonadotrophin-releasing hormone (GnRH) antagonist co-treatment] together with the transfer of one embryo, versus conventional stimulation (with GnRH agonist long protocol co-treatment) and the transfer of two embryos. Outcome measures are: (i) pregnancies resulting in term live birth; (ii) total costs per term live birth; and (iii) patient stress/discomfort per started IVF treatment, over a 12 month period. Power considerations for this study were an overall cumulative live birth rate of 45% for the conventional treatment strategy, with non-inferiority of the mild treatment strategy defined as a live birth rate no more than 12.5% lower compared with the conventional study arm. For a power of 80% and alpha of 0.05, 400 subjects are required.

RESULTS

As planned, from February 2002 until February 2004, 410 patients were enrolled.

CONCLUSIONS

This effectiveness study applies an integrated medical, health economics and psychological approach with term live birth over a given period of time after starting IVF as the end-point. Complete and timely patient enrolment vindicates many of the design decisions.

Economic evaluation of the administration of follitropin-beta with a pen device

Previous studies suggest that administration of follitropin-beta with a pen device (Puregon Pen(R)) is more convenient, less painful and 16-18% more efficient. The aim of this study was to perform an economic evaluation of the administration of follitropin-beta by this pen device against follitropin-alpha by multidose and highly purified (HP) HMG by conventional syringe in IVF treatment by comparing the process utilities and the costs for the Dutch setting. Conjoint analysis assessed the process utilities for the three administration modes on a scale from 0 to 1. A decision analytic model estimated the costs of an average IVF cycle from a societal perspective. Patients estimated the process utility at 0.96 for the pen, 0.53 for the multidose and 0.36 for the conventional syringe. Additional costs were estimated at 0 Euros and 194 Euros, comparing the pen with multidose or conventional methods respectively. Assuming a 16% efficiency gain of the pen, costs ranged from Euros-135 (savings) to 60 Euros (extra costs). In conclusion, patients perceive sufficient benefits to the pen device to choose it over other dosing methods. Dominance of the pen device over the multidose method was shown. Compared with the conventional administration method, the added value of the pen device was 2.7 (0.96/0.36) times higher.

Cumulative live birth rates in cohorts of patients treated with in vitro fertilization or intracytoplasmic sperm injection

OBJECTIVE

Follow-up of IVF/intracytoplasmic sperm injection (ICSI) patients to obtain accurate information concerning chances of live birth as well as early treatment dropout. Comparison of the cumulative pregnancy rates, established in cohorts, with those estimated with life table analysis to determine which method provides the most accurate data without overestimation.

DESIGN

Retrospective longitudinal cohort study.

SETTING

Academic medical IVF center.

PATIENT(S)

All 750 patients from the Leiden IVF center and another 706 patients from cooperating clinics starting IVF/ICSI treatment in the period 1996-2000.

INTERVENTION(S)

All observations were part of standard IVF/ICSI and cryopreservation protocols.

MAIN OUTCOME MEASURE(S)

Endpoints of this study were a first live birth or termination of treatment. Treatment cycles were followed until the end of 2002, pregnancy follow-up through September 2003.

RESULT(S)

The cumulative live birth rate for the Leiden cohort was 59.1%. In yearly cohorts this varied from 54.8% to 67.1%. Cumulative live birth rates were 61.8%-63.2% for unexplained infertility (n = 229), endometriosis (n = 19), and andrologic indication (n = 223). For tubal (n = 129) and hormonal (n = 46) indications the rates were 55.8% and 45.7%, respectively. The group of egg donation or surrogacy (n = 10) reached 40.0%, and patients with two or more indications (n = 84) 56.0%. For women < or = 35 years of age the cumulative live birth rate was 64.6%, for women 36-39 years of age it was 48.7%, and for women 40-42 years of age 31.0%.

CONCLUSION(S)

In contrast to estimation of expected cumulative pregnancy rates the cohort measurement does not overestimate success rates. It accurately reflects chances of both live birth as well as early treatment dropout. The cumulative live birth rate was 59.1%. Over time results improved and the contribution of cryopreservation increased.

Ten years of Swiss National IVF Register FIVNAT-CH. Are we making progress?

In 2001, analysis of Swiss data collected since 1993 included 1001 treatment cycles with IVF, 2217 treatment cycles with intracytoplasmic sperm injection and 2160 treatment cycles with frozen-thawed embryos or zygotes. IVF cycle number has remained constant over the past 10 years, now representing only 18% of the total. ICSI treatment cycles have plateaued since 2001. Altogether, patients receive 1.56 treatment cycles per year, nearly constant since 1995. Mean maternal age has increased from 33.9 to 35.7 years, while mean number of recovered oocytes has increased by 1.3. Considerable improvement was seen in clinical pregnancy rate after 'fresh' treatment cycles since 2000. Mean number of replaced embryos in 'fresh' treatment cycles has fallen to below 2.5 since 1996, long before the legal imposition of the three-embryo transfer limit in 2001, and is still decreasing without affecting the consistent twin pregnancy rate of 19%. The frequency of ovarian hyperstimulation syndrome has increased three-fold. External audits have reduced the mean number of errors per data file by half, and increased the number of correct files by 20%. Data collected over this 10-year period show that despite the introduction of a restrictive law and increasing mean maternal age, the overall clinical pregnancy rate has continued to improve.

FSH: what is the highest dose for ovarian stimulation that makes sense on an evidence-based level?

The widely applied practice of a gonadotrophin dose increase in case of low response is not on an evidence-based level and not efficacious. All known comparative studies failed to show a difference in favour of the high-dose group regarding their pregnancy rate per embryo transfer. However if more oocytes and more embryos are available for cryopreservation, the real benefit in terms of cumulative pregnancy outcome might be with the high-dose regimen. This publication will show - as a review of the literature - that the frequent clinical practice of increasing the FSH dose does not lead to a higher pregnancy rate, which is in line with recommendation for milder stimulation regimes in IVF. Thus, the collective evidence to date would suggest that 150 IU/day to 250 IU/day of FSH or human menopausal gonadotrophin (HMG) is an appropriate starting dose for most women undergoing ovarian hyperstimulation for IVF as part of a gonadotrophin-releasing hormone (GnRH) antagonist or a long GnRH agonist protocol.

Mild stimulation in in vitro fertilization

Current approaches to ovarian stimulation for in vitro fertilization (IVF) are aimed at optimizing the number of oocytes retrieved in a treatment cycle. This approach is not without risks. Moreover, as the true costs of multiple pregnancy become clearer, the need to produce multiple embryos for transfer is increasingly questioned. Increasing knowledge of the physiological mechanisms involved in follicular development and dominance has led to new strategies in ovarian stimulation for IVF. The clinical availability of GnRH antagonists allows the normal cycle to be harnessed and manipulated by mild interventions to produce sufficient oocytes for successful IVF treatment. Recent evidence suggests that oocyte quality after mild stimulation may be superior to that after conventional stimulation regimens.

Embryo disposal practices in IVF clinics in the United States

BACKGROUND

The moral status of the human embryo is particularly controversial in the United States, where one debate has centered on embryos created in excess at in vitro fertilization (IVF) clinics. Little has been known about the disposal of these embryos.

METHODS

We mailed anonymous, self-administered questionnaires to directors of 341 American IVF clinics.

RESULTS

217 of 341 clinics (64 percent) responded. Nearly all (97 percent) were willing to create and cryopreserve extra embryos. Fewer, but still a majority (59 percent), were explicitly willing to avoid creating extras. When embryos did remain in excess, clinics offered various options: continual cryopreservation for a charge (96 percent) or for no charge (4 percent), donation for reproductive use by other couples (76 percent), disposal prior to (60 percent) or following (54 percent) cryopreservation, and donation for research (60 percent) or embryologist training (19 percent). Qualifications varied widely among those personnel responsible for securing couples' consent for disposal and for conducting disposal itself. Some clinics performed a religious or quasi-religious disposal ceremony. Some clinics required a couple's participation in disposal; some allowed but did not require it; some others discouraged or disallowed it.

CONCLUSIONS

The disposal of human embryos created in excess at American IVF clinics varies in ways suggesting both moral sensitivity and ethical divergence.

Cryopreservation as a tool to reduce multiple birth

The potential role of embryo cryopreservation from the point of view of prevention of multiple pregnancies is analysed. Cryopreservation is an unavoidable option in stimulated IVF/intracytoplasmic sperm injection (ICSI), but at the same time an underestimated tool in the prevention of twins. There is a need for an evaluation system not only of the cryotechnology process per se, but also of the true augmenting effect of cryopreservation on the total reproductive potential of a single oocyte harvest. Only cryopregnancies occurring after an unsuccessful fresh cycle (possibly followed by one or more unsuccessful freeze-thaw cycles with embryos from the same harvest) truly reflect the augmentation potential of cryopreservation. This potential is greater than generally thought. First, the efficacy of cryopreservation is suboptimal with survival rates between 30 and 70%. Second, if single-embryo transfer were applied in a much larger proportion of cycles than is presently the case, more embryos would be available for cryopreservation, resulting in more and more successful freeze-thaw cycles. In the future, the combination of elective single-embryo transfer with an optimized cryopreservation programme is likely to become the standard of care for routine IVF/ICSI treatment.