Preimplantation diagnosis of common aneuploidies by the first- and second-polar body FISH analysis

Mechanism of chromosomal mosaicism in preimplantation embryos and its effect on embryo development

Aneuploidy is one of the main causes of miscarriage and in vitro fertilization failure. Mitotic abnormalities in preimplantation embryos are the main cause of mosaicism, which may be influenced by several endogenous factors such as relaxation of cell cycle control mechanisms, defects in chromosome cohesion, centrosome aberrations and abnormal spindle assembly, and DNA replication stress. In addition, incomplete trisomy rescue is a rare cause of mosaicism. However, there may be a self-correcting mechanism in mosaic embryos, which allows some mosaicisms to potentially develop into normal embryos. At present, it is difficult to accurately diagnose mosaicism using preimplantation genetic testing for aneuploidy. Therefore, in clinical practice, embryos diagnosed as mosaic should be considered comprehensively based on the specific situation of the patient.

Preimplantation genetic testing: A remarkable history of pioneering, technical challenges, innovations, and ethical considerations

Preimplantation genetic testing (PGT) has emerged as a powerful companion to assisted reproduction technologies. The origins and history of PGT are reviewed here, along with descriptions of advances in molecular assays and sampling methods, their capabilities, and their applications in preventing genetic diseases and enhancing pregnancy outcomes. Additionally, the potential for increasing accuracy and genome coverage is considered, as well as some of the emerging ethical and legislative considerations related to the expanding capabilities of PGT.

Live birth per embryo transfer with next generation sequencing preimplantation genetic testing: an analysis of 26,107 cycles

The technique and platform used for preimplantation genetic testing for aneuploidy (PGT-A) have undergone significant changes over time. The contemporary technique utilizes trophectoderm biopsy followed by next-generation sequencing (NGS). The goal of this study was to explore the role of PGT-A using NGS technique exclusively in contemporary in vitro fertilization (IVF) practice. For this, we performed a retrospective analysis of a large dataset collected from the Shady Grove Fertility (SGF) multicentre practice. All autologous IVF cycles which were followed by at least one single embryo transfer (ET) (fresh and/or frozen) between January 2017 to July 2020, were included. Our study group included patients who had PGT-A and the control group included patients who did not proceed with PGT-A. The primary outcome was the live birth rate (LBR) per transfer. All age-adjusted LBR was higher in the PGT-A group than the non-PGT-A group (48.9% vs. 42.7%, p < 0.001), except in women <35 years old among single embryo frozen ETs. Similarly, LBR in the PGT-A group was higher in all ages except in women <35 years old (48.7% vs. 41.7%, p < 0.001) when all single embryos fresh and frozen ETs were included. In patients of decreased ovarian reserve, transfer of euploid embryo was associated with higher LBR (46.7% vs. 26.7%, p < 0.001) whereas miscarriages were lower in patients with unexplained infertility (9.3% vs. 11.3%, p = 0.007 and endometriosis (8.9% vs. 11.6%, p < 0.001) following euploid embryo transfer. To conclude, the transfer of euploid embryos tested via NGS PGT-A was associated with improved LBR per transfer in women ≥35 years old.

Exploring the Impact of Controlled Ovarian Stimulation and Non-Invasive Oocyte Assessment in ART Treatments

Invasive and noninvasive features are normally applied to select developmentally competent oocytes and embryos that can increase the take-home baby rates in assisted reproductive technology. The noninvasive approach mainly applied to determine oocyte and embryo competence has been, since the early days of IVF, the morphological evaluation of the mature cumulus-oocyte complex at the time of pickup, first polar body, zona pellucida thickness, perivitelline space and cytoplasm appearance. Morphological evaluation of oocyte quality is one of the options used to predict successful fertilization, early embryo development, uterine implantation and the capacity of an embryo to generate a healthy pregnancy to term. Thus, this paper aims to provide an analytical revision of the current literature relating to the correlation between ovarian stimulation procedures and oocyte/embryo quality. In detail, several aspects of oocyte quality such as morphological features, oocyte competence and its surrounding environment will be discussed. In addition, the main noninvasive features as well as novel approaches to biomechanical parameters of oocytes that might be correlated with the competence of embryos to produce a healthy pregnancy and live birth will be illustrated.

We have reached a dead end for preimplantation genetic testing for aneuploidy

The hypothesis of preimplantation genetic testing for aneuploidy (PGT-A) was first proposed 20 years ago, suggesting that during IVF elimination of aneuploid embryos prior to transfer will improve implantation rates of remaining embryos and, therefore, increase pregnancy and live birth rates, while also reducing miscarriages. Subsequently, unvalidated and increasingly unrestricted clinical utilization of PGT-A called for at least one properly randomized controlled trial (RCT) to assess cumulative live birth rates following a single oocyte retrieval, utilizing all fresh and frozen embryos of an IVF cycle. Only recently two such RCTs were published, however both, when properly analysed, not only failed to demonstrate significant advantages from utilization of PGT-A, but actually demonstrated outcome deficits in comparison to non-use of PGT-A, when patient selection biases in favour of PGT-A were reversed. Moreover, because of high embryo mosaicism at the blastocyst stage and, therefore, high false-positive rates from trophectoderm biopsies, large numbers of chromosomal-normal embryos with normal pregnancy potential are unnecessarily left unused or discarded, indisputably causing harm to affected couples. We, therefore, strongly call for restricting PGT-A to only research protocols and, as of this point in time, encourage professional societies in the field to follow suit with appropriate practice guidelines.

Comment on the recent PGDIS Position Statement on the Transfer of Mosaic Embryos 2021

The worldwide demand of preimplantation genetic testing for aneuploidy (PGT-A) is still growing. However, chromosomal mosaic results greatly challenge the clinical practice. The recently published PGDIS Position Statement on the Transfer of Mosaic Embryos is the third PGDIS position statement on how to deal with embryos diagnosed as chromosomal mosaics (CM) and, one of many attempts of different societies and working groups to provide a guideline for clinicians, laboratories, clinics, and genetic counselors. But still, as in previous statements, many issues remained unresolved. Moreover, from our point of view, the question how to deal with embryos diagnosed as CM, consisting of two or more karyological cell lines cannot be separated from all the other aspects of PGT-A including its accuracy. The paucity of clearcut indications for PGT-A and evidence of benefit as well as an overall cost-benefit assessment is given below.

Combining PGT-A with PGT-M risks trying to do too much

The primary objective of preimplantation genetic testing for monogenic disorders (PGT-M) is to avoid having a child with a serious monogenic disease. Combining testing for unrelated sporadic chromosomal abnormalities (PGT-A) and excluding embryos with chromosomally abnormal results from transfer proffers the chance to mitigate the risk of miscarriage and to reduce the number of embryo transfers, but also risks excluding healthy embryos from transfer due to abnormal test results that do not reflect the true potential of the embryo. The theoretical utility of combining PGT-M with PGT-A is explored in this communication. It is concluded that PGT-M without PGT-A is preferred to achieve an unaffected live birth. Since PGT-M is mostly undertaken by couples where the female partner is younger than 35 years, PGT-A is likely to marginally mitigate the risk of miscarriage. Experimental non-selection studies are needed to assess the potential detrimental effect of combining PGT-M with PGT-A in a clinical setting.

Non-invasive oocyte quality assessment

Oocyte quality is perhaps the most important limiting factor in female fertility; however, the current methods of determining oocyte competence are only marginally capable of predicting a successful pregnancy. We aim to review the predictive value of non-invasive techniques for the assessment of human oocytes and their related cells and biofluids that pertain to their developmental competence. Investigation of the proteome, transcriptome, and hormonal makeup of follicular fluid, as well as cumulus-oocyte complexes are currently underway; however, prospective randomized non-selection-controlled trials of the future are needed before determining their prognostic value. The biological significance of polar body morphology and genetics are still unknown and the subject of debate. The predictive utility of zygotic viscoelasticity for embryo development has been demonstrated, but similar studies performed on oocytes have yet to be conducted. Metabolic profiling of culture media using human oocytes are also limited and may require integration of automated, high-throughput targeted metabolomic assessments in real time with microfluidic platforms. Light exposure to oocytes can be detrimental to subsequent development and utilization of time-lapse imaging and morphometrics of oocytes is wanting. Polarized light, Raman microspectroscopy, and coherent anti-Stokes Raman scattering are a few novel imaging tools that may play a more important role in future oocyte assessment. Ultimately, the integration of chemistry, genomics, microfluidics, microscopy, physics, and other biomedical engineering technologies into the basic studies of oocyte biology, and in testing and perfecting practical solutions of oocyte evaluation, are the future for non-invasive assessment of oocytes.

Utilization of preimplantation genetic testing in the USA

PURPOSE

To evaluate the use of preimplantation genetic testing (PGT) and live birth rates (LBR) in the USA from 2014 to 2017 and to understand how PGT is being used at a clinic and state level.

METHODS

This study accessed SART data for 2014 to 2017 to determine LBR and the CDC for years 2016 and 2017 to identify PGT usage. Primary cycles included only the first embryo transfer within 1 year of an oocyte retrieval; subsequent cycles included transfers occurring after the first transfer or beyond 1 year of oocyte retrieval.

RESULTS

In the SART data, the number of primary PGT cycles showed a significant monotonic annual increase from 18,805 in 2014 to 54,442 in 2017 (P = 0.042) and subsequent PGT cycles in these years increased from 2946 to 14,361 (P = 0.01). There was a significant difference in primary PGT cycle use by age, where younger women had a greater percentage of PGT treatment cycles than older women. In both PGT and non-PGT cycles, the LBR per oocyte retrieval decreased significantly from 2014 to 2017 (P<0001) and younger women had a significantly higher LBR per oocyte retrieval compared to older women (P < 0.001). The CDC data revealed that in 2016, just 53 (11.4%) clinics used PGT for more than 50% of their cycles, which increased to 99 (21.4%) clinics in 2017 (P< 0.001).

CONCLUSIONS

A growing number of US clinics are offering PGT to their patients. These findings support re-evaluation of the application for PGT.

Depletion of aneuploid cells in human embryos and gastruloids

Chromosomal instability leading to aneuploidy is pervasive in early human embryos^1-3 and is considered as a major cause of infertility and pregnancy wastage^4,5. Here we provide several lines of evidence that blastocysts containing aneuploid cells are worthy of in vitro fertilization transfer. First, we show clinically that aneuploid embryos can lead to healthy births, suggesting the presence of an in vivo mechanism to eliminate aneuploidy. Second, early development and cell specification modelled in micropatterned human 'gastruloids' grown in confined geometry show that aneuploid cells are depleted from embryonic germ layers, but not from extraembryonic tissue, by apoptosis in a bone morphogenetic protein 4 (BMP4)-dependent manner. Third, a small percentage of euploid cells rescues embryonic tissue in mosaic gastruloids when mixed with aneuploid cells. Finally, single-cell RNA-sequencing analysis of early human embryos revealed a decline of aneuploidy beginning on day 3. Our findings challenge two current dogmas: that a single trophectoderm biopsy at blastocyst stage to perform prenatal genetic testing can accurately determine the chromosomal make-up of a human embryo, and that aneuploid embryos should be withheld from embryo transfer in association with in vitro fertilization.

Preimplantation Genetic Testing for Aneuploidy - a Castle Built on Sand

Preimplantation genetic testing for aneuploidy (PGT-A) has become a routine add-on for in vitro fertilization (IVF) to determine whether human embryos are to be clinically utilized or disposed of. Studies claiming IVF outcome improvements following PGT-A, however, used highly selected patient populations or inappropriate statistical methodologies. PGT-A was never clinically validated in its ability to define a human embryo as chromosomal normal, mosaic, or aneuploid, nor certified by a regulatory body, or an authoritative professional organization. Because of a high false-positive rate, PGT-A, actually reduces live IVF birth chances for many patients. Furthermore, in recent studies the PGT-A hypothesis was demonstrated to be mistaken for biological, mathematical and technical reasons. PGT-A, therefore, should clinically only be offered within experimental study frameworks.

The dawn of the future: 30 years from the first biopsy of a human embryo. The detailed history of an ongoing revolution

Following early studies showing no adverse effects, cleavage stage biopsy by zona drilling using acid Tyrode's solution, and removal of single blastomeres for preimplantation genetic testing (PGT) and identification of sex in couples at risk of X-linked disease, was performed by Handyside and colleagues in late 1989, and pregnancies reported in 1990. This method was later used for specific diagnosis of monogenic conditions, and a few years later also for chromosomal structural and/or numerical impairments, thereby establishing a valuable alternative option to prenatal diagnosis. This revolutionary approach in clinical embryology spread worldwide, and several other embryo biopsy strategies developed over three decades in a process that is still ongoing. The rationale of this narrative review is to outline the different biopsy approaches implemented across the years in the workflow of the IVF clinics that provided PGT: their establishment, the first clinical experiences, their downsides, evolution, improvement and standardization. The history ends with a glimpse of the future: minimally/non-invasive PGT and experimental embryo micromanipulation protocols. This grand theme review outlines a timeline of the evolution of embryo biopsy protocols, whose implementation is increasing worldwide together with the increasing application of PGT techniques in IVF. It represents a vade mecum especially for the past, present and upcoming operators and experts in this field to (re)live this history from its dawn to its most likely future.

The PGS/PGT-A controversy in IVF addressed as a formal conflict resolution analysis

PURPOSE

To use conflict resolution analysis on the conflict between proponents and opponents of preimplantation genetic testing for aneuploidy (PGT-A), previously called preimplantation genetic screening (PGS).

METHODS

Considered in conflict analysis a case study, we reviewed the English literature based on key-word searches at www.pubmed.com and www.google.com, and interviewed professional opinion leaders and other actor-representatives. This analysis was the product of a mandated externship by L.M. at the Foundation for Reproductive Medicine (FRM), as part of the Master of Science Program in Negotiations and Conflict Resolution at Columbia University, New York, NY.

RESULTS

Initially a typical difference of opinion, conflict evolved after proponents rejected studies that failed to confirm expected benefits, and authors felt demeaned by their criticism. Becoming "destructive," the conflict evolved according to Glasl's escalation model stages. Proponents became continuous attractors. Unable to produce validations for PGT-A, proponents moved goal posts through 3 stages (PGS 1.0-PGS 3.0). Ultimately concurring that pregnancy and live birth rates are unaffected, they started claiming new benefits.

CONCLUSIONS

The FRM underwrote this study as a starting tool for a conflict resolution process. A consensus building conference of stakeholders appears as of this point to represent the most promising potential intervention. The goal of such a conference should be sustainable consensus about clinical utilization of PGS/PGT-A in IVF, based on transparent and validated criteria. A potential date for such a conference is set for 2020.

A tale of two studies: now is no longer the best of times for preimplantation genetic testing for aneuploidy (PGT-A)

Preimplantation genetic testing for aneuploidy (PGT-A) does not create normal embryos, but selecting a viable embryo for a fresh transfer has the potential to deliver an extra effect for live birth from a stimulated cycle by evading the attrition associated with embryo cryopreservation. Improved genetic tests are now available for selecting viable embryos; however, current embryo cryopreservation techniques also have a superior survival rate, which means it is now possible to transfer most morphologically suitable embryos from a stimulated cycle one at a time. The cumulative live birth rate from a stimulated cycle is now unlikely to be superior compared with morphological assessment alone, with any benefit likely to be associated with a reduction in the risk of miscarriage and the time to pregnancy. This communication offers a perspective on the likely benefit and disbenefit of PGT-A based on the outcome of modern-day clinical studies. Caution should be advised regarding offering PGT-A to every woman. Quantifying the likely miscarriage benefit and live birth disbenefit for an appropriate patient group may help to better inform couples who might be considering adding aneuploidy screening to their treatment cycle.

Preimplantation genetic diagnosis (PGD) and genetic testing for aneuploidy (PGT-A): status and future challenges

The world's first in vitro fertilization (IVF) baby was born in July 1978 in the UK. Since then, more than 7 million infants have been born worldwide as a result of IVF. Preimplantation genetic diagnosis (PGD) was introduced in the late 1980s for couples at risk of transmitting a genetic abnormality to their children. From the mid-1990s, this technology has been employed as an embryo selection tool for patients undergoing IVF and has been known as preimplantation genetic screening (PGS). The aim of this practice has been to identify and select euploid embryos for transfer, in order to increase efficacy of IVF cycle, ensure higher implantation rates or at least decreased time to pregnancy. In the early days, fluorescent in situ hybridization (FISH) technology was used for genetic analysis. New advancements in both biopsy and cytogenetic have made possible the improvement of PGD and PGT-A analysis. Currently, a variety of technologies have been implemented to individuate euploid embryos to be preferentially transferred in IVF treatments. The purpose of this review is to clarify the differences between PGD and PGT-A, and to discuss current indications and requirements for embryo biopsy and genetic methodologies used.

Single best euploid versus single best unknown-ploidy blastocyst frozen embryo transfers: a randomized controlled trial

PURPOSE

This paper aims to investigate the efficacy of IVF with preimplantation genetic testing for aneuploidy (PGT-A), using only best-scoring blastocysts from young (≤ 35 years) infertile patients undergoing single blastocyst frozen embryo transfers (FET).

METHOD

In this randomized controlled trial (RCT) registered 29 March 2017, 302 infertile patient-couples eligible to participate underwent autologous ICSI blastocyst freeze-all cycles. Two-hundred and twenty patient-couples satisfied the inclusion criteria (i.e., female age ≤ 35 years, two-day 5 ≥ 2BB blastocysts) and were randomized to either the PGT-A (PGT-A group, n = 109) selection arm or morphology score (morphology group, n = 111) selection arm. In both arms, the highest ranking (by morphological score) blastocysts were selected for FET.

RESULTS

Of the 109 best-scoring blastocysts that underwent PGT-A, 80 were predicted to be euploid (73.4%) and were transferred in FET (euploid subgroup). There was no statistical difference in LB rate between the euploid subgroup and morphology group (56.3% vs 58.6%, odds ratio 0.91 (95% CI 0.51-1.63), p = 0.750). In a multiple logistic regression, the transfer of euploid blastocysts was not found to be a significant predictor of LB when adjusting for female age, infertility duration, antral follicle count, and blastocyst quality, with the independent odds expressed as 0.91 (95% CI 0.50-1.66, p = 0.760).

CONCLUSION

In young (≤ 35 years) infertile patients with at least two ≥ 2BB blastocysts, PGT-A blastocyst selection does not result in an enhanced LB rate, with the evidence suggesting that the effectivity of PGT-A may be limited by the effectivity of TE biopsy.

TRIAL REGISTRATION

ClinicalTrials.gov ID: NCT03095053.

Expected advances in human fertility treatments and their likely translational consequences

BACKGROUND

Due to rapid research progress in reproductive biology and reproductive clinical endocrinology, many human infertility treatments are close to potential breakthroughs and translational applications. We here review current barriers, where such breakthroughs will likely come from, what they will entail, and their potential clinical applications.

MAIN TEXT

The radical nature of change will primarily benefit older women, reduce fertility treatment costs and thereby expand access to treatment. A still widely overlooked prerequisite for implantation and normal pregnancy maintenance is timely development of maternal immunological tolerance toward an implanting paternal semi-allograft, if malfunctioning associated with implantation failure and pregnancy loss, while premature termination of tolerance appears associated with premature labor, pre-eclampsia/eclampsia and gestoses of pregnancy. Common denominators between pregnancy and invasive malignancies have again been attracting attention, suggesting that, like in malignant tumors, degrees of embryo aneuploidy may affect invasiveness and ability to "disarm" the immune system's innate response against implanting embryos. Linking tolerance to implantation, we offer evidence that the so-called "implantation window" is likely immunological rather than hormonally defined.

CONCLUSIONS

Because many here outlined treatment changes will disproportionally benefit older women, they will exert a pronounced effect on society, as increasing numbers of women at grandparental ages will become mothers.

Principles guiding embryo selection following genome-wide haplotyping of preimplantation embryos

STUDY QUESTION

How to select and prioritize embryos during PGD following genome-wide haplotyping?

SUMMARY ANSWER

In addition to genetic disease-specific information, the embryo selected for transfer is based on ranking criteria including the existence of mitotic and/or meiotic aneuploidies, but not carriership of mutations causing recessive disorders.

WHAT IS KNOWN ALREADY

Embryo selection for monogenic diseases has been mainly performed using targeted disease-specific assays. Recently, these targeted approaches are being complemented by generic genome-wide genetic analysis methods such as karyomapping or haplarithmisis, which are based on genomic haplotype reconstruction of cell(s) biopsied from embryos. This provides not only information about the inheritance of Mendelian disease alleles but also about numerical and structural chromosome anomalies and haplotypes genome-wide. Reflections on how to use this information in the diagnostic laboratory are lacking.

STUDY DESIGN, SIZE, DURATION

We present the results of the first 101 PGD cycles (373 embryos) using haplarithmisis, performed in the Centre for Human Genetics, UZ Leuven. The questions raised were addressed by a multidisciplinary team of clinical geneticist, fertility specialists and ethicists.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Sixty-three couples enrolled in the genome-wide haplotyping-based PGD program. Families presented with either inherited genetic variants causing known disorders and/or chromosomal rearrangements that could lead to unbalanced translocations in the offspring.

MAIN RESULTS AND THE ROLE OF CHANCE

Embryos were selected based on the absence or presence of the disease allele, a trisomy or other chromosomal abnormality leading to known developmental disorders. In addition, morphologically normal Day 5 embryos were prioritized for transfer based on the presence of other chromosomal imbalances and/or carrier information.

LIMITATIONS, REASONS FOR CAUTION

Some of the choices made and principles put forward are specific for cleavage-stage-based genetic testing. The proposed guidelines are subject to continuous update based on the accumulating knowledge from the implementation of genome-wide methods for PGD in many different centers world-wide as well as the results of ongoing scientific research.

WIDER IMPLICATIONS OF THE FINDINGS

Our embryo selection principles have a profound impact on the organization of PGD operations and on the information that is transferred among the genetic unit, the fertility clinic and the patients. These principles are also important for the organization of pre- and post-counseling and influence the interpretation and reporting of preimplantation genotyping results. As novel genome-wide approaches for embryo selection are revolutionizing the field of reproductive genetics, national and international discussions to set general guidelines are warranted.

STUDY FUNDING/COMPETING INTEREST(S)

The European Union's Research and Innovation funding programs FP7-PEOPLE-2012-IAPP SARM: 324509 and Horizon 2020 WIDENLIFE: 692065 to J.R.V., T.V., E.D. and M.Z.E. J.R.V., T.V. and M.Z.E. have patents ZL910050-PCT/EP2011/060211-WO/2011/157846 ('Methods for haplotyping single cells') with royalties paid and ZL913096-PCT/EP2014/068315-WO/2015/028576 ('Haplotyping and copy-number typing using polymorphic variant allelic frequencies') with royalties paid, licensed to Cartagenia (Agilent technologies). J.R.V. also has a patent ZL91 2076-PCT/EP20 one 3/070858 ('High throughout genotyping by sequencing') with royalties paid.

TRIAL REGISTRATION NUMBER

N/A.

Is the hypothesis of preimplantation genetic screening (PGS) still supportable? A review

The hypothesis of preimplantation genetic diagnosis (PGS) was first proposed 20 years ago, suggesting that elimination of aneuploid embryos prior to transfer will improve implantation rates of remaining embryos during in vitro fertilization (IVF), increase pregnancy and live birth rates and reduce miscarriages. The aforementioned improved outcome was based on 5 essential assumptions: (i) Most IVF cycles fail because of aneuploid embryos. (ii) Their elimination prior to embryo transfer will improve IVF outcomes. (iii) A single trophectoderm biopsy (TEB) at blastocyst stage is representative of the whole TE. (iv) TE ploidy reliably represents the inner cell mass (ICM). (v) Ploidy does not change (i.e., self-correct) downstream from blastocyst stage. We aim to offer a review of the aforementioned assumptions and challenge the general hypothesis of PGS. We reviewed 455 publications, which as of January 20, 2017 were listed in PubMed under the search phrase < preimplantation genetic screening (PGS) for aneuploidy>. The literature review was performed by both authors who agreed on the final 55 references. Various reports over the last 18 months have raised significant questions not only about the basic clinical utility of PGS but the biological underpinnings of the hypothesis, the technical ability of a single trophectoderm (TE) biopsy to accurately assess an embryo’s ploidy, and suggested that PGS actually negatively affects IVF outcomes while not affecting miscarriage rates. Moreover, due to high rates of false positive diagnoses as a consequence of high mosaicism rates in TE, PGS leads to the discarding of large numbers of normal embryos with potential for normal euploid pregnancies if transferred rather than disposed of. We found all 5 basic assumptions underlying the hypothesis of PGS to be unsupported: (i) The association of embryo aneuploidy with IVF failure has to be reevaluated in view how much more common TE mosaicism is than has until recently been appreciated. (ii) Reliable elimination of presumed aneuploid embryos prior to embryo transfer appears unrealistic. (iii) Mathematical models demonstrate that a single TEB cannot provide reliable information about the whole TE. (iv) TE does not reliably reflect the ICM. (v) Embryos, likely, still have strong innate ability to self-correct downstream from blastocyst stage, with ICM doing so better than TE. The hypothesis of PGS, therefore, no longer appears supportable. With all 5 basic assumptions underlying the hypothesis of PGS demonstrated to have been mistaken, the hypothesis of PGS, itself, appears to be discredited. Clinical use of PGS for the purpose of IVF outcome improvements should, therefore, going forward be restricted to research studies.

The Past, Present, and Future of Preimplantation Genetic Testing

Preimplantation genetic testing (PGT) of oocytes and embryos is the earliest form of prenatal testing. PGT requires in vitro fertilization for embryo creation. In the past 25 years, the use of PGT has increased dramatically. The indications of PGT include identification of embryos harboring single-gene disorders, chromosomal structural abnormalities, chromosomal numeric abnormalities, and mitochondrial disorders; gender selection; and identifying unaffected, HLA-matched embryos to permit the creation of a savior sibling. PGT is not without risks, limitations, or ethical controversies. This review discusses the techniques and clinical applications of different forms of PGT and the debate surrounding its associated uncertainty and expanded use.

Preimplantation genetic diagnosis: an update on current technologies and ethical considerations

The aim of reproductive medicine is to support the birth of healthy children. Advances in assisted reproductive technologies and genetic analysis have led to the introduction of preimplantation genetic diagnosis (PGD) for embryos. Indications for PGD have been a major topic in the fields of ethics and law. Concerns vary by nation, religion, population, and segment, and the continued rapid development of new technologies. In contrast to the ethical augment, technology has been developing at an excessively rapid speed. The most significant recent technological development provides the ability to perform whole genome amplification and sequencing of single embryonic cells by microarray or next-generation sequencing methods. As new affordable technologies are introduced, patients are presented with a growing variety of PGD options. Simultaneously, the ethical guidelines for the indications for testing and handling of genetic information must also rapidly correspond to the changes.

Age-related increase in aneuploidy and alteration of gene expression in mouse first polar bodies

PURPOSE

To confirm that aneuploidy candidate genes are detectable in the first polar body (PB(1)) of MII oocytes and to investigate the age-dependent molecular changes in PB(1).

METHODS

Aged (12-to 15-mo-old) and young (2-mo-old) mice were administered pregnant mare's serum gonadotropin (PMSG) and human chorionic gonadotrophin (hCG). MII oocytes were obtained and the first PB was removed. mRNA from each PB and its sibling oocyte was reverse transcribed. Real-time PCR was performed to quantify the expression of six genes (BUB1, CDC20, Filia, MCAK, SGOL1, SMC1A) in single PB.

RESULTS

We first demonstrated that detection and quantification of transcripts associated with aneuploidy in single mouse oocyte and sibling PB(1) is possible and the relative abundance of mRNA transcripts in a single PB faithfully reflects the relative abundance of that transcript in its sibling oocyte. We further found that transcript levels were significantly lower in aged PBs compared with young PBs (P<0.05).

CONCLUSIONS

Our results suggest that the detection and analysis of polar body mRNA may provide insight in age-related aneuploidy in oocyte. This analysis is a novel concept to investigate the genesis of chromosome abnormality and could potentially assist in the characterization of mechanisms underlying key molecular origin of female meiotic aneuploidy, which would be of great scientific and clinical value.

Polar bodies in assisted reproductive technology: current progress and future perspectives

During meiotic cell-cycle progression, unequal divisions take place, resulting in a large oocyte and two diminutive polar bodies. The first polar body contains a subset of bivalent chromosomes, whereas the second polar body contains a haploid set of chromatids. One unique feature of the female gamete is that the polar bodies can provide beneficial information about the genetic background of the oocyte without potentially destroying it. Therefore, polar body biopsies have been applied in preimplantation genetic diagnosis to detect chromosomal or genetic abnormalities that might be inherited by the offspring. Besides the traditional use in preimplantation diagnosis, recent findings suggest additional important roles for polar bodies in assisted reproductive technology. In this paper, we review the new roles of polar bodies in assisted reproductive technology, mainly focusing on single-cell sequencing of the polar body genome to deduce the genomic information of its sibling oocyte and on polar body transfer to prevent the transmission of mtDNA-associated diseases. We also discuss additional potential roles for polar bodies and related key questions in human reproductive health. We believe that further exploration of new roles for polar bodies will contribute to a better understanding of reproductive health and that polar body manipulation and diagnosis will allow production of a greater number of healthy babies.

Chromosomes in the porcine first polar body possess competence of second meiotic division within enucleated MII stage oocytes

To determine whether chromosomes in the porcine first polar body (PB1) can complete the second meiotic division and subsequently undergo normal pre-implantation embryonic development, we examined the developmental competence of PB1 chromosomes injected into enucleated MII stage oocytes by nuclear transfer method (chromosome replacement group, CR group). After parthenogenetic activation (PA) or in vitro fertilization (IVF), the cleavage rate of reconstructed oocytes in the IVF group (CR-IVF group, 36.4 ± 3.2%) and PA group (CR-PA group, 50.8 ± 4.2%) were significantly lower than that of control groups in which normal MII oocytes were subjected to IVF (MII-IVF group, 75.8 ± 1.5%) and PA (MII-PA group, 86.9 ± 3.7%). Unfertilized rates was significantly higher in the CR-IVF group (48.6 ± 3.3%) than in the MII-IVF group (13.1 ± 3.4%). The blastocyst formation rate was 8.3 ± 1.9% in the CR-PA group, whereas no blastocyst formation was observed in the CR-IVF group. To produce tetraploid parthenogenetic embryos, intact MII stage oocytes injected with PB1 chromosomes were electrically stimulated, treated with 7.5 μg/mL cytochalasin B for 3 h (MII oocyte + PB1 + CB group), and then cultured without cytochalasin B. The average cleavage rate of reconstructed oocytes was 72.5% (48 of 66), and the blastocyst formation rate was 18.7% (9 of 48). Chromosome analysis showed similar proportions of haploid and diploid cells in the control (normal MII oocytes) and CR groups after PA; overall, 23.6% of blastocysts were tetraploid in the MII oocyte + PB1 + CB group. These results demonstrate that chromosomes in PB1 can participate in normal pre-implantation embryonic development when injected into enucleated MII stage oocytes, and that tetraploid PA blastocysts are produced (although at a low proportion) when PB1 chromosomes are injected into intact MII stage oocytes.

The root of reduced fertility in aged women and possible therapentic options: current status and future perspects

It is well known that maternal ageing not only causes increased spontaneous abortion and reduced fertility, but it is also a high genetic disease risk. Although assisted reproductive technologies (ARTs) have been widely used to treat infertility, the overall success is still low. The main reasons for age-related changes include reduced follicle number, compromised oocyte quality especially aneuploidy, altered reproductive endocrinology, and increased reproductive tract defect. Various approaches for improving or treating infertility in aged women including controlled ovarian hyperstimulation with intrauterine insemination (IUI), IVF/ICSI-ET, ovarian reserve testing, preimplantation genetic diagnosis and screening (PGD/PGS), oocyte selection and donation, oocyte and ovary tissue cryopreservation before ageing, miscarriage prevention, and caloric restriction are summarized in this review. Future potential reproductive techniques for infertile older women including oocyte and zygote micromanipulations, derivation of oocytes from germ stem cells, ES cells, and iPS cells, as well as through bone marrow transplantation are discussed.

Preimplantation genetic testing: indications and controversies

In the last two decades, the use of preimplantation genetic testing has increased dramatically. This testing is used for identifying singlegene disorders, chromosomal abnormalities, mitochondrial disorders, gender selection in non-mendelian disorders with unequal gender distribution, aneuploidy screening, and other preconceptually identified genetic abnormalities in prospective parents. Genetic testing strategies and diagnostic accuracy continues to improve, but not without risks or controversies. In this review the authors discuss the techniques and clinical application of preimplantation genetic diagnosis, and the debate surrounding its associated uncertainty and expanded use.

Spindle and chromosome configurations of human oocytes matured in vitro in two different culture media

In-vitro maturation can have deleterious effects on spindle formation and proper chromosome alignment in human oocytes and can be profoundly affected by culture conditions. This study compared the spindle presence and location with the maturation rate of germinal vesicle (GV) oocytes cultured in two different media: G1.2 and G1.2 supplemented with follicle-stimulating hormone, human chorionic gonadotrophin and 17beta-oestradiol. A total of 304 oocytes were retrieved from 101 women undergoing IVF treatment with intracytoplasmic sperm injection. Spindle presence was recorded using the Polscope. Spindle morphology was evaluated with immunocytological staining for alpha-tubulin and chromatin. Twenty-one in-vitro matured oocytes with the presence of spindle and ten of their corresponding polar bodies (PB) were also assessed for aneuploidy. A significantly increased maturation rate (69.7%) was observed after 24h in the supplemented culture media compared with the G1.2 media (56.6%; P<0.05). The proportions of metaphase II (MII) oocytes with spindle presence and abnormal spindle morphology were similar in the two culture media. Also, 76.9% of MII and 70% of PB had chromosomal abnormalities. In conclusion, supplementing culture media may increase the oocyte maturation rate in vitro, but does not necessarily indicate the presence of a birefringent spindle, or normal spindle and chromosomal alignment.

Molecular methods for selection of the ideal oocyte

Some recent strategies for identifying the ideal oocyte for insemination in assisted reproduction techniques are reviewed. Established methods of assessing the female gamete, such as morphological evaluation of oocytes and cytogenetic analysis of polar bodies using fluorescence in-situ hybridization, will soon be joined by more advanced cytogenetic methods such as the use of comparative genomic hybridization to improve understanding of oocyte genetics. It seems likely, however, that the greatest advances will originate from the evolution of molecular genetic technologies. The application of microarray technology to individual oocytes and their associated cumulus cells has recently been accomplished, providing a simultaneous assessment of activity for thousands of genes and revealing potential viability markers. Furthermore, improved equipment and optimized methods of mass spectrometry have provided sufficient sensitivity to allow proteomic profiles to be generated from single oocytes and embryos, while metabolomic investigations have searched for indicators of oocyte/embryo quality in spent culture medium. Techniques of this type may ultimately lead to non-invasive tests for oocyte quality revealing previously hidden information concerning both oocyte and embryo developmental competence. Once fully validated, these new approaches are expected to revolutionize oocyte and embryo selection, leading to improved implantation rates and higher probabilities of success using elective single embryo transfer.

Haemophilia A: molecular insights

Haemophilia A is the most common inherited bleeding disorder caused by defects in the

Clin Chem Lab Med 2007;45:450–61.

The contradictory information on the distribution of non-disjunction and pre-division in female gametes

Valuable information on the cytogenetic constitution of female gametes has been deduced from the direct, so-called conventional analysis of oocytes remaining unfertilized in programmes of assisted reproduction. Additional, indirect conclusions have become possible by PGD of the polar bodies. Both techniques provided evidence for the co-existence of two aneuploidy-causing mechanisms during first maternal meiosis; non-disjunction (ND) of bivalents results in the loss or gain of whole chromosomes in metaphase II complements, whereas a precocious division (pre-division, PD) of univalents leads to the loss or gain of single chromatids. As to the distribution of ND and PD, however, direct oocyte chromosome studies and PGD tell surprisingly different stories. Moreover, first and second polar body analyses contradict the data derived from DNA polymorphism studies concerning the distribution of first and second meiotic division errors. An increased awareness of these problems appears necessary because important decisions are made on the basis of PGD results.

Molecular cytogenetic studies towards the full karyotype analysis of human blastocysts and cytotrophoblasts

Numerical chromosome aberrations in gametes typically lead to failed fertilization, spontaneous abortion or a chromosomally abnormal fetus. By means of preimplantation genetic diagnosis (PGD), we now can screen human embryos in vitro for aneuploidy before transferring the embryos to the uterus. PGD allows us to select unaffected embryos for transfer and increases the implantation rate in in vitro fertilization programs. Molecular cytogenetic analyses using multi-color fluorescence in situ hybridization (FISH) of blastomeres have become the major tool for preimplantation genetic screening of aneuploidy. However, current FISH technology can test for only a small number of chromosome abnormalities and hitherto failed to increase the pregnancy rates as expected. We are in the process of developing multi-color FISH-based technologies to score all 24 chromosomes in single cells within a three-day time limit, which we believe is vital to the clinical setting. Also, human placental cytotrophoblasts (CTBs) at the fetal-maternal interface acquire aneuploidies as they differentiate to an invasive phenotype. About 20-50% of invasive CTB cells from uncomplicated pregnancies were found to be aneuploid, suggesting that the acquisition of aneuploidy is an important component of normal placentation, perhaps limiting the proliferative and invasive potential of CTBs. Since most invasive CTBs are interphase cells and possess extreme heterogeneity, we applied multi-color FISH and repeated hybridizations to investigate the feasibility of a full karyotype analysis of individual CTBs. In summary, this study demonstrates the strength of Spectral Imaging analysis and repeated hybridizations, which provides a basis for full karyotype analysis of single interphase cells.

Frequency and distribution of chromosome abnormalities in human oocytes

It was previously shown that more than half of the human oocytes obtained from IVF patients of advanced reproductive age are aneuploid, due to meiosis I and meiosis II errors. The present paper further confirms that 61.8% of the oocytes tested by fluorescent probes specific for chromosomes 13, 16, 18, 21 and 22 are abnormal, representing predominantly chromatid errors, which are the major source of aneuploidy in the resulting embryos. Almost half of the oocytes with meiosis I errors (49.3%) are prone to sequential meiosis II errors, which may lead to aneuploidy rescue in 30.8% of the cases. Half of the detected aneuploidies (49.8%) are of complex nature with involvement of two or more chromosomes, or the same chromosome in both meiotic divisions. The aneuploidy rates for individual chromosomes are different, with a higher prevalence of chromosome 21 and 22 errors. The origin of aneuploidy for the individual chromosomes is also not random, with chromosome 16 and 22 errors originating more frequently in meiosis II, and chromosome 18, 13 and 21 errors in meiosis I. There is an age dependence not only for the overall frequency of aneuploidies, but also for each chromosome error, aneuploidies originating from meiosis I, meiosis II, and both meiosis I and meiosis II errors, as well as for different types of aneuploidies. The data further suggest the practical relevance of oocyte aneuploidy testing for detection and avoidance from transfer of the embryos deriving from aneuploid oocytes, which should contribute significantly to the pregnancy outcomes of IVF patients of advanced reproduction age.

Chromosome abnormalities and their relationship to morphology and development of human embryos

This review covers the relationship between chromosome abnormalities, morphological abnormalities and embryonic development. The baseline of chromosome abnormalities in human embryos produced by assisted reproduction is higher than 50%, regardless of maternal age. While aneuploidy increases with maternal age, abnormalities arising post-meiotically, such as mosaicism, chaoticism, polyploidy and haploidy, have similar incidence in all age groups (about 33%). Post-meiotic abnormalities do increase with dysmorphism. The most common dysmorphisms found in cleavage-stage embryos are multinucleation, fragmentation and uneven cells, among others. All dysmorphisms are associated with an increase in post-meiotic chromosome abnormalities and a decreased implantation potential. Similarly, embryos developing slowly or with arrested development have higher incidence of post-meiotic abnormalities than normally developing ones. Chromosome studies in blastocysts indicate that mosaicism is the most common abnormality but that the load of abnormal cells decreases with increasing blastocyst quality. Regardless of blastocyst quality, more than 40% of mosaics are still chromosomally abnormal and will not implant or will spontaneously abort. Because aneuploidy is not related to cleavage stage dysmorphism and trisomies can reach blastocyst stage and beyond, morphological analysis is not enough to select against chromosome abnormalities, and thus preimplantation genetic diagnosis should be recommended in patients 35 and older.

Preimplantation genetic diagnosis for aneuploidy screening in repeated implantation failure

Chromosomal abnormalities are thought to be responsible for implantation failure, and among chromosomal abnormalities in normally developing embryos, aneuploidy is the most frequent. Genetic testing of preimplantation embryos for chromosomal aneuploidy allows selection of chromosomally normal embryos, and early detection of chromosomal aberration will increase the chance of conceiving. Preimplantation genetic diagnosis for aneuploidy screening (PGD-AS), performed by polar body or blastomere analysis, is used in infertile patients treated with assisted reproduction technologies, especially in those with a poor prognosis, e.g. repeated IVF failure, advanced maternal age, or recurrent spontaneous abortion. The aim of this paper is to clarify the impact of PGD-AS in repeated implantation failure. In this review, the data collected so far regarding PGD-AS in this patient group will be discussed in depth.

Meiotic and mitotic nondisjunction: lessons from preimplantation genetic diagnosis

Direct testing of the outcome of the first and second meiotic divisions has become possible with the introduction of preimplantation genetic diagnosis (PGD) for aneuploidies. Testing of oocytes by fluorescent in situ hybridization (FISH) analysis of the first and second polar bodies showed that more than half of oocytes from the IVF patients aged 35 years and older had chromosomal abnormalities, which originated from errors in meiosis I or meiosis II, or both: 41.9% of oocytes were aneuploid after meiosis I and 37.3% aneuploid after meiosis II, with 29.1% of these oocytes having both meiosis I and meiosis II errors. As a result, one third of oocytes detected as normal after meiosis I contained the meiosis II errors, and two thirds of those with meiosis II errors were already abnormal following meiosis I. Although the rates of chromosomal abnormalities deriving from meiosis I and II were comparable, meiosis I errors predominantly resulted in extra chromosome (chromatid) material in oocytes, in contrast to a random distribution of extra and missing chromatids after meiosis II. The majority of meiosis I abnormalities were represented by chromatid errors, which seem to be the major source of chromosomal abnormalities in the resulting embryos. Approximately one third of aneuploid oocytes deriving from sequential errors in the first and second meiotic divisions resulted in a balanced karyotype, representing a possible phenomenon of "aneuploidy rescue" during the second meiotic division. However, the majority of the embryos resulting from such oocytes appeared to be abnormal for the same or different chromosome(s), or were mosaic, suggesting a possible predisposition of the resulting embryos to further mitotic errors. Although the origin of a high frequency of mosaicism at the cleavage stage is not sufficiently understood, the mosaic embryos may originate from the chromosomally abnormal oocytes, as a result of a "trisomy rescue" mechanism during the first mitotic divisions, which renders polar body FISH analysis to have important clinical value for reliable pre-selection of aneuploidy-free embryos for transfer.

ESHRE PGD Consortium ‘Best practice guidelines for clinical preimplantation genetic diagnosis (PGD) and preimplantation genetic screening (PGS)’

Among the many educational materials produced by the European Society of Human Reproduction and Embryology (ESHRE) are guidelines. ESHRE guidelines may be developed for many reasons but their intent is always to promote best quality practices in reproductive medicine. In an era in which preimplantation genetic diagnosis (PGD) has become a reality, we must strive to maintain its efficacy and credibility by offering the safest and most effective treatment available. The dominant motivators for the development of current comprehensive guidelines for best PGD practice were (i) the absence of guidelines and/or regulation for PGD in many countries and (ii) the observation that no consensus exists on many of the clinical and technical aspects of PGD. As a consequence, the ESHRE PGD Consortium undertook to draw up guidelines aimed at giving information, support and guidance to potential, fledgling and established PGD centres. The success of a PGD treatment cycle is the result of great attention to detail. We have strived to provide a similar level of detail in this document and hope that it will assist staff in achieving the best clinical outcome for their patients.

Microtubule turnover in ooplasm biopsy reflects ageing phenomena in the parent oocyte

Oviductal oocytes retrieved from superovulated B6D2F1 mice at 13.5, 16 and 19 h after human chorionic gonadotrophin (HCG) (groups A, B and C respectively, n = 382) were micromanipulated to obtain 12-20 mum sized ooplasm biopsy fragments. Experiments were divided into three sets. Ooplasmic microtubule dynamics were studied in ooplasm biopsy specimens and parent oocytes (set 1) and ooplasm biopsy specimens (set 2), whilst zona pellucida dissolution time, cortical granule loss and spindle/chromatin morphology using confocal microscopy were also studied in parent oocytes (set 2). Oocytes withstood oocyte biopsy with a high survival rate (98.2%) and the biopsied oocytes underwent successful fertilization and development (set 3). An absolute one-to-one correlation was seen between the oocyte biopsy specimens and the parent oocytes in terms of ooplasmic microtubule dynamics (set 1), and increased ooplasmic microtubule dynamics in oocyte biopsy specimens paralleled ageing phenomena in the parent oocytes (set 2). Zona pellucida dissolution time was significantly lower in parent oocytes from group A versus groups B (P = 0.032), and C (P < 0.001). (Groups A, B, C include minimal, moderate, increased ooplasmic microtubule dynamics in oocyte biopsy specimens respectively.) Oocyte cortical granule loss and spindle/chromatin abnormalities were mainly seen in group C (P < 0.001). Oocyte biopsy can thus be applied to judge age-related changes in the parent oocytes.

Influence of maternal age on the outcome of PGD for aneuploidy screening in patients with recurrent implantation failure

This study assessed the influence of maternal age on the outcome of aneuploidy screening (AS) cycles for recurrent implantation failure (RIF). One hundred and sixteen couples with a history of RIF underwent 130 cycles of AS. Group A included 78 patients aged < or = 40 years (range 25-40 years) who underwent 86 cycles, while group B included 38 couples aged > or = 41 (range 41-47) who underwent 44 cycles. Fluorescence in-situ hybridization (FISH) analysis of the first and second polar bodies using probes specific for chromosomes 13, 16, 18, 21 and 22 was conducted. Euploid oocytes that cleaved were subsequently tested using the same probes on a single blastomere obtained from day 3 embryos. Chromosomally normal embryos were replaced on day 5 of culture. There was no significant difference between the two groups in the mean numbers of oocytes fertilized normally and oocytes (7.5 +/- 3.2 versus 7.2 +/- 3.6) and embryos tested (4.1 +/- 3 versus 3.4 +/-3). However, the younger age group had a significantly higher proportion of euploid oocytes/embryos, cycles reaching embryo transfer, pregnancy (43 versus 25%), clinical pregnancy (36.1 versus 16.6%) and ongoing delivery (32 versus 12.5%) rates per transfer. Preimplantation genetic diagnosis with AS for recurrent IVF implantation failure using FISH probes is therefore associated with improved outcome in women under 41 years, but has a high cancellation rate and low cycle outcome in older women.

Preimplantation diagnosis (PGD)--a European clinician's point of view

This paper describes the current status of preimplantation diagnosis from the viewpoint of an experienced clinician specialized in reproductive medicine. Current progress and international experiences with different applications and techniques are being reviewed on the basis of the literature. Particular interest is focused on possible advantages of routinely diagnosing major chromosome aneuploidies in preimplantation-embryos of patients undergoing in vitro fertilization and embryo transfer. Last but not least, a short survey of the international guidelines and legislation is compared to the situation in the author's country, Austria, where it is currently unclear whether preimplantation diagnosis is allowed or not.

Investigation of chromosomal imbalance in human embryos using comparative genomic hybridization

Studies of cleavage-stage human embryos using fluorescence in-situ hybridization (FISH) to identify sub-sets of chromosomes have indicated that the incidence of chromosomal abnormalities is high. Whole genome amplification (WGA) and comparative genomic hybridization (CGH) to investigate the full chromosome complement applied to a small number of human embryos suggested an even higher rate of abnormality. WGA and CGH were used to identify genomic imbalance in individual blastomeres from human embryos, and the results were correlated with FISH analysis of sibling blastomeres. Forty embryos were analysed; 17 (42.5%) had a normal diploid karyotype and 23 (57.5%) were abnormal, with a chromosome imbalance in one or more cells including three (7.5%) that had a chaotic chromosome complement. Of the abnormal embryos, only three showed consistent aneuploidy. FISH results obtained from sibling blastomeres were in agreement with the CGH results in all 22 of the embryos where both tests were informative. It is concluded that rates of meiotic aneuploidy in human embryos may be lower than previous estimates. The results indicate that chromosomally abnormal embryos were more likely to have arisen as a result of cultural artefact or inadequate cell cycle surveillance, rather than meiotic error.

Karyotyping of human metaphase II oocytes by multifluor fluorescence in situ hybridization

OBJECTIVE

To quantify aneuploidy in inseminated, injected, and noninjected oocytes from infertility patients using Multifluor fluorescence in situ hybridization (M-FISH).

DESIGN

Prospective study.

SETTING

Reproductive biology group, academic unit of pediatrics, obstetrics, and gynecology.

PATIENT(S)

Forty-eight patients undergoing ovarian stimulation and either intracytoplasmic sperm injection (ICSI) or conventional in vitro fertilization (IVF).

INTERVENTION(S)

None.

MAIN OUTCOME MEASURE(S)

M-FISH karyotyping of 67 metaphase II oocytes, including noninjected in vitro matured oocytes, and injected inseminated-failed fertilized oocytes.

RESULT(S)

Thirty-nine percent of oocytes were aneuploid, with nondisjunction of chromosomes in 34% of oocytes and predivision of chromatids in 10%. There was no difference in aneuploidy rates between ICSI noninjected in vitro matured oocytes and injected, failed fertilized oocytes. Chromosomes most frequently involved in aneuploidy were 15, 18, 19, 22, and X. In seven injected ICSI MII oocytes, the prematurely condensed sperm chromatin was karyotyped by M-FISH.

CONCLUSION(S)

M-FISH was used to diagnose aneuploidy at maternal meiosis I in 39% of oocytes, and M-FISH karyotyping of sperm was demonstrated.

Improved implantation after preimplantation genetic diagnosis of aneuploidy

The objective of this study was to assess the improvement in implantation rates after preimplantation genetic diagnosis (PGD) of numerical abnormalities for the sole indication of advanced maternal age when compared with a control group. Each PGD patient was matched to a control patient according to several parameters prior to obtaining pregnancy results. The diagnosis was based on the analysis of chromosomes X, Y, 13, 15, 16, 18, 21 and 22 plus a ninth probe (1, 7, 14 or 17) on a single cell per embryo. The results were also analysed in relation to the previous number of IVF cycles and the number of dipronucleated zygotes obtained, when replacing presumptively chromosomally normal embryos on day 4 of development. It was found that women of advanced reproductive age (average age 40 years) had a higher implantation rate (18%) than their matched controls treated with standard IVF (11%) (P < 0.05). This increase was not observed in patients with two or more previous IVF cycles or patients with fewer than eight zygotes. Patients with eight or more 2PN zygotes and one or no previous cycles showed the greatest improvement in implantation rate, from 8.8% in controls to 19.2% in the PGD group (average age 40 years) (P < 0.025).