The beneficial effects of preimplantation genetic diagnosis for aneuploidy support extensive clinical application

Novel ploidy analysis in ectopic pregnancy

Objective

To study whether a single-nucleotide polymorphism (SNP) array could be used to test tissue from ectopic pregnancy to distinguish whether ectopic pregnancies were aneuploid.

Design

Case series report.

Setting

Academic medical center.

Patients

One hundred seventy-eight women who underwent surgery for ectopic pregnancy at Northwestern Memorial Hospital between 2015 and 2018 were eligible for participation; written consent was obtained from 33 patients. Eight subjects had sufficient DNA samples and were included in the analysis. Maternal and paternal DNA samples were self-collected by buccal swab. Archived paraffin tissue containing chorionic villi from each surgically removed ectopic specimen was analyzed using SNP microarray technology to determine chromosome number and evaluate for maternal cell contamination.

Interventions

None.

Main Outcome Measures

Prevalence of aneuploidy in ectopic pregnancy specimens as well as success of SNP array technology in formalin-fixed and paraffin-embedded specimens.

Results

Subjects had a mean (±SD) age of 33.4 ± 5.4 years, body mass index of 23.4 ± 5.7 kg/m², 3.3 ± 1.8 prior pregnancies, and 1.5 ± 1.4 live births. Genetic testing revealed that all eight tested samples were euploid, 6 female and 2 male (two arr(1-22)x2, (X,Y)x1 and 6 arr(1-22, X)x2); maternal cell contamination was ruled out in all cases.

Conclusions

This study showed proof of concept for the use of routinely stored formalin-fixed, paraffin-embedded tissue blocks with DNA extraction for SNP array to detect ploidy status of ectopic pregnancy. Although all tested samples were euploid, further research is needed to gain a definitive answer to this question and better understand the mechanism that leads to ectopic implantation.

Sperm chromosome abnormalities in patients with normal karyotype and in translocation carriers: clinical relevance for assisted reproductive technology

RESEARCH QUESTION

What is the proportion of chromosomally abnormal spermatozoa in men with a history of reproductive failure, including patients with normal karyotype and carriers of translocations? Should this analysis be included in a clinical setting to define the best treatment options for infertile couples?

DESIGN

Aneuploidy for chromosomes XY, 13, 15, 16, 17, 18, 21, 22 was tested by fluorescent in-situ hybridization (FISH) in 1665 samples from couples with normal karyotype having had at least three previous IVF failures, miscarriages, or both (group-A). A FISH test was also carried out in 76 samples from carriers of translocations (group B) to detect the proportion of spermatozoa with unbalanced rearrangement.

RESULTS

In group A, the lowest incidence of aneuploid sperm cells was found in men with normozoospermia (1.3%, range 0.09-6.31%) compared with men with moderate oligoasthenoteratozoospermia (2.1%, range 0.41-16.6%, P < 0.001), severe oligoasthenoteratozoospermia (4.7%, range 0.53-30.77, P < 0.001), microepididymal sperm aspiration (3.1%, range 1.19-24.24, P < 0.001) and testicular sperm extraction samples (5.8%, range 1.54-33.3, P < 0.001). In group B, the proportion of spermatozoa with unbalanced rearrangement was significantly higher in reciprocal (63%, range 10.0-87.6%) than in Robertsonian translocations (16%, range 4.3-51.0%, P < 0.001).

CONCLUSIONS

Patients with poor prognosis of term pregnancy tend to generate high proportions of chromosomally abnormal spermatozoa, especially in severe male factor cases. Corresponding frequencies occur at wide ranges; therefore, the FISH test is needed to assess the proportion of spermatozoa with altered chromosome condition. A flowchart, which included the FISH test, was designed to assist clinicians guide couples with poor prognosis of pregnancy, on the most indicated treatment options.

Overview of Preimplantation Genetic Diagnosis (PGD): Historical Perspective and Future Direction

Preimplantation genetic diagnosis (PGD) can be considered the earliest form of prenatal testing. It was first used in humans over 26 years ago. At its inception, PGD could only be performed for a limited number of genetic disorders. Technological advances in molecular biology and cytogenomics have been utilized in the field of PGD to greatly expand the spectrum of genetic disorders that can now be detected in early human embryos.

Chromosomal analysis in IVF: just how useful is it?

Designed to minimize chances of genetically abnormal embryos, preimplantation genetic diagnosis (PGD) involves in vitro fertilization (IVF), embryo biopsy, diagnosis and selective embryo transfer. Preimplantation genetic testing for aneuploidy (PGT-A) aims to avoid miscarriage and live born trisomic offspring and to improve IVF success. Diagnostic approaches include fluorescence in situ hybridization (FISH) and more contemporary comprehensive chromosome screening (CCS) including array comparative genomic hybridization (aCGH), quantitative polymerase chain reaction (PCR), next-generation sequencing (NGS) and karyomapping. NGS has an improved dynamic range, and karyomapping can detect chromosomal and monogenic disorders simultaneously. Mosaicism (commonplace in human embryos) can arise by several mechanisms; those arising initially meiotically (but with a subsequent post-zygotic 'trisomy rescue' event) usually lead to adverse outcomes, whereas the extent to which mosaics that are initially chromosomally normal (but then arise purely post-zygotically) can lead to unaffected live births is uncertain. Polar body (PB) biopsy is the least common sampling method, having drawbacks including cost and inability to detect any paternal contribution. Historically, cleavage-stage (blastomere) biopsy has been the most popular; however, higher abnormality levels, mosaicism and potential for embryo damage have led to it being superseded by blastocyst (trophectoderm - TE) biopsy, which provides more cells for analysis. Improved biopsy, diagnosis and freeze-all strategies collectively have the potential to revolutionize PGT-A, and there is increasing evidence of their combined efficacy. Nonetheless, PGT-A continues to attract criticism, prompting questions of when we consider the evidence base sufficient to justify routine PGT-A? Basic biological research is essential to address unanswered questions concerning the chromosome complement of human embryos, and we thus entreat companies, governments and charities to fund more. This will benefit both IVF patients and prospective parents at risk of aneuploid offspring following natural conception. The aim of this review is to appraise the 'state of the art' in terms of PGT-A, including the controversial areas, and to suggest a practical 'way forward' in terms of future diagnosis and applied research.

Impact of sperm genome decay on Day-3 embryo chromosomal abnormalities from advanced-maternal-age patients

Infertile male patients often exhibit unconventional semen parameters, including DNA fragmentation, chromatin dispersion, and aneuploidy-collectively referred to as sperm genome decay (SGD). We investigated the correlation of SGD to embryo chromosomal abnormalities and its effect on clinical pregnancy rates in patients with advanced maternal age (AMA) (>40 years) who were undergoing intracytoplasmic sperm injection-preimplantation genetic screening (ICSI-PGS). Three groups were assessed: patients with AMA and male partners with normal sperm (AMA-N); AMA patients and male partners presenting with SGD (AMA-SGD); and young fertile female patients and male partners with SGD (Y-SGD). We found a significant increase in embryonic chromosomal abnormalities-polyploidy, nullisomy, mosaicism, and chaotic anomaly rates-when semen parameters are altered (76% vs. 67% and 66% in AMA-SGD vs. AMA-N and Y-SGD groups, respectively). Statistical analysis showed a correlation between SGD and aneuploidies of embryonic chromosomes 13, 16, 21, X, and Y, as well as negative clinical outcomes. Incorporation of molecular sperm analyses should therefore significantly minimize the risk of transmission of chromosomal anomalies from spermatozoa to embryos, and may provide better predictors of pregnancy than conventional sperm analyses. We also demonstrated that an ICSI-PGS program should be implemented for SGD patients in order to limit transmission of chromosomal paternal anomalies and to improve clinical outcome.

Is preimplantation genetic diagnosis the ideal embryo selection method in aneuploidy screening?

To select cytogenetically normal embryos, preimplantation genetic diagnosis (PGD) aneuploidy screening (AS) is used in numerous centers around the world. Chromosomal abnormalities lead to developmental problems, implantation failure, and early abortion of embryos. The usefulness of PGD in identifying single-gene diseases, human leukocyte antigen typing, X-linked diseases, and specific genetic diseases is well-known. In this review, preimplantation embryo genetics, PGD research studies, and the European Society of Human Reproduction and Embryology PGD Consortium studies and reports are examined. In addition, criteria for embryo selection, technical aspects of PGD-AS, and potential noninvasive embryo selection methods are described. Indications for PGD and possible causes of discordant PGD results between the centers are discussed. The limitations of fluorescence in situ hybridization, and the advantages of the array comparative genomic hybridization are included in this review. Although PGD-AS for patients of advanced maternal age has been shown to improve in vitro fertilization outcomes in some studies, to our knowledge, there is not sufficient evidence to use advanced maternal age as the sole indication for PGD-AS. PGD-AS might be harmful and may not increase the success rates of in vitro fertilization. At the same time PGD, is not recommended for recurrent implantation failure and unexplained recurrent pregnancy loss.

Knowledge and Educational Needs about Pre-Implantation Genetic Diagnosis (PGD) among Oncology Nurses

Preimplantation genetic diagnosis (PGD), a form of assisted reproductive technology, is a new technology with limited awareness among health care professionals and hereditary cancer families. Nurses play a key role in the care of patients and are often in an ideal position to discuss and refer patients on sensitive quality of life issues, such as PGD. Two hundred and one nurses at Moffitt Cancer Center (MCC) responded to an online survey assessing knowledge and educational needs regarding PGD and families with hereditary cancer. The majority of respondents were female (n = 188), white (n = 175), had an RN/BSN degree (n = 83), and provided outpatient care at the cancer center (n = 102). More than half of respondents (78%) were unfamiliar with PGD prior to the survey and respondents who had heard of PGD had limited knowledge. More than half of the participants reported PGD was an acceptable option for families with hereditary cancer syndromes and thought individuals with a strong family or personal history should be provided with information about PGD. This study indicates that oncology nurses may benefit from and desire education about PGD. With advances in reproductive technology and options, further PGD education is needed among healthcare professionals. An examination of current oncology nursing curriculum and competencies regarding genetic education may identify need for future revisions and updates.

Morphological good-quality embryo has higher nucleus spreading rate/signal resolution rate in fluorescence in situ hybridization

PURPOSE

To evaluate the relationship between day 3 embryo quality and nucleus spreading rate/signal resolution rate in Fluorescence in situ hybridization (FISH) during the PGD procedure.

METHODS

This study was a retrospective data analysis. 367 day-3 embryos were classified based on morphological scoring: grade 1 to grade 4 were defined from worse to better embryo quality. Day 3 embryos were classified as good quality when the number of blastomeres was between 6 and 10 and grade better than 2'. Nucleus spreading rate, signal rate and the full signal rate were compared between embryos with different morphological scoring.

RESULTS

Nucleus spreading rate of blastomeres from morphological high-quality embryos was significantly higher (86.25 %) than from poor-quality embryos (76.53 %) (p < 0.05). The rate of blastomeres with full signals was significantly higher (79.32 %) in the morphological high-quality group than in poor-quality group (64.54 %) (p < 0.05). Similar results were found from day 3 embryos with cell number between 6 cells and 10 cells (nucleus spreading rate 86.01 vs. 76.34 %, p < 0.05; full signal rate 78.72 vs. 62.71 %, p < 0.05). Both have no significant difference in the signal rate (82.67 vs. 89.66 %; 83.10 vs. 89.95 %).

CONCLUSIONS

Blastomeres from day 3 embryos with better morphological quality had higher nucleus spreading rate and higher full signal rate during FISH. Through this study, we speculate on whether it should reconsider the necessity of FISH application in embryos with poor quality.

[Preimplantation diagnosis--PID: preimplantation genetic diagnosis (PGD) and preimplantation genetic screening (PGS)]

Preimplantation diagnosis (PID) comprises all the relevant diagnostic procedures for the investigation of genetic, structural, or numerical changes of the genetic information in spermatozoa and oocytes as well as in embryos after in vitro fertilization (IVF) or intracytoplasmic sperm injection (ICSI). PID of oocytes is well established in Germany for the above-mentioned indications. PID at the embryonic level, i.e., trophectoderm biopsy of blastocysts, is possible in centers with proven expertise in reproductive medicine and human genetics. A high risk for genetic disease in the child or a high likelihood for stillbirth or miscarriage is a prerequisite for PID. A specialized ethics committee is required to look into each case before making a decision. While PID is still under development in Germany, it has been a well-established technology worldwide for 24 years. International experience in PID and the resulting implications are discussed in this article.

Preimplantation genetic diagnosis for aneuploidy and translocations using array comparative genomic hybridization

At least 50% of human embryos are abnormal, and that increases to 80% in women 40 years or older. These abnormalities result in low implantation rates in embryos transferred during in vitro fertilization procedures, from 30% in women <35 years to 6% in women 40 years or older. Thus selecting normal embryos for transfer should improve pregnancy results. The genetic analysis of embryos is called Preimplantation Genetic Diagnosis (PGD) and for chromosome analysis it was first performed using FISH with up to 12 probes analyzed simultaneously on single cells. However, suboptimal utilization of the technique and the complexity of fixing single cells produced conflicting results. PGD has been invigorated by the introduction of microarray testing which allows for the analysis of all 24 chromosome types in one test, without the need of cell fixation, and with staggering redundancy, making the test much more robust and reliable. Recent data published and presented at scientific meetings has been suggestive of increased implantation rates and pregnancy rates following microarray testing, improvements in outcome that have been predicted for quite some time. By using markers that cover most of the genome, not only aneuploidy can be detected in single cells but also translocations. Our validation results indicate that array CGH has a 6Mb resolution in single cells, and thus the majority of translocations can be analyzed since this is also the limit of karyotyping. Even for translocations with smaller exchanged fragments, provided that three out of the four fragments are above 6Mb, the translocation can be detected.

Preimplantation genetic diagnosis to improve pregnancy outcomes in subfertility

Pre-implantation genetic diagnosis provides prenatal genetic diagnosis before implantation, thus allowing detection of chromosomal abnormalities and their exclusion from embryo transfer in assisted reproductive technologies. Polar body, blastomere or trophectoderm can each be used to obtain requisite genetic or embryonic DNA. Pre-implantation genetic diagnosis for excluding unbalanced translocations is well accepted, and pre-implantation genetic diagnosis aneuploidy testing to avoid repeated pregnancy losses in couples having recurrent aneuploidy is efficacious in reducing miscarriages. Controversy remains about whether pre-implantation genetic diagnosis aneuploidy testing improves take home pregnancy rates, for which reason adherence to specific indications is recommended while the issue is being adjudicated. Current recommendations are for obligatory 24 chromosome testing, most readily using array comparative genome hybridisation.

PGS-FISH in reproductive medicine and perspective directions for improvement: a systematic review

INTRODUCTION

Embryo selection can be carried out via morphological criteria or by using genetic studies based on Preimplantation Genetic Screening. In the present study, we evaluate the clinical validity of Preimplantation Genetic Screening with fluorescence in situ hybridization (PGS-FISH) compared with morphological embryo criteria.

MATERIAL AND METHODS

A systematic review was made of the bibliography, with the following goals: firstly, to determine the prevalence of embryo chromosome alteration in clinical situations in which the PGS-FISH technique has been used; secondly, to calculate the statistics of diagnostic efficiency (negative Likelihood Ratio), using 2 × 2 tables, derived from PGS-FISH. The results obtained were compared with those obtained from embryo morphology. We calculated the probability of transferring at least one chromosome-normal embryo when it was selected using either morphological criteria or PGS-FISH, and considered what diagnostic performance should be expected of an embryo selection test with respect to achieving greater clinical validity than that obtained from embryo morphology.

RESULTS

After an embryo morphology selection that produced a negative result (normal morphology), the likelihood of embryo aneuploidies was found to range from a pre-test value of 65% (prevalence of embryo chromosome alteration registered in all the study groups) to a post-test value of 55% (Confidence interval: 50-61), while after PGS-FISH with a negative result (euploid), the post-test probability was 42% (Confidence interval: 35-49) (p < 0.05). The probability of transferring at least one euploid embryo was the same whether 3 embryos were selected according to morphological criteria or whether 2, selected by PGS-FISH, were transferred. Any embryo selection test, if it is to provide greater clinical validity than embryo morphology, must present a LR-value of 0.40 (Confidence interval: 0.32-0.51) in single embryo transfer, and 0.06 (CI: 0.05-0.07) in double embryo transfer.

DISCUSSION

With currently available technology, and taking into account the number of embryos to be transferred, the clinical validity of PGS-FISH, although superior to that of morphological criteria, does not appear to be clinically relevant.

Preimplantation genetic diagnosis at 20 years

First reported in 1990, PGD has evolved into a complementary form of prenatal diagnosis offering novel indications. DNA for PGD can be recovered with equal safety and facility from polar bodies I and II, blastomere (8 cell embryo) and trophectoderm (5-6 day blastocyst). Diagnostic accuracy is very high (>99%) for both chromosomal abnormalities and single gene disorders. Traditional application of FISH with chromosome specific probes for detecting aneuploidy and translocations may be replaced or complemented by array comparative genome hybridization (array CGH); biopsied embryos can now be cryopreserved (vitrification) while analysis proceeds in orderly fashion. PGD has been accomplished for over 200 different single gene disorders. Novel indications for PGD not readily applicable by traditional prenatal genetic diagnosis include avoiding clinical pregnancy termination, performing preconceptional diagnosis (polar body I), obtaining prenatal diagnosis without disclosure of prenatal genotype (nondisclosure), diagnosing adult-onset disorders particularly cancer, and identifying HLA compatible embryos suitable for recovering umbilical cord blood stem cells.

Analysis of pronuclear zygote configurations in 459 clinical pregnancies obtained with assisted reproductive technique procedures

BACKGROUND

Embryos selection is crucial to maintain high performance in terms of pregnancy rate, reducing the risk of multiple pregnancy during IVF. Pronuclear and nucleolar characteristics have been proposed as an indicator of embryo development and chromosomal complement in humans, providing information about embryo viability.

METHODS

To correlate the zygote-score with the maternal age and the outcome of pregnancy, we analyzed the pronuclear and nucleolar morphology, the polar body alignment and the zygote configuration in 459 clinical pregnancies obtained by IVF and ICSI in our public clinic in Reggio Emilia, Italy. We derived odds ratios (OR) and Corenfield's 95% confidence intervals (CI). Continuous variables were compared with Student's t-test; P lower than .05 was considered statistically significant.

RESULTS

We observed a significant increase of "A" pronuclear morphology configuration in 38-41 years old patients in comparison to that lower than or equal to 32 years old and a significant decrease of "B" configuration in 38-41 years old patients in comparison to that lower than or equal to 32 and in comparison to that of 33-37 years old. Related to maternal age we found no significant differences in P1 and in P2 configuration. We found no correlation between zygote-score, embryo cleavage and embryo quality.

CONCLUSIONS

Our results confirm the limited clinical significance of zygote-score suggesting that it can not be associated with maternal age, embryo cleavage and embryo quality. The evaluation of embryo quality based on morphological parameters is probably more predictive than zygote-score.

Are zona pellucida laser drilling and polar body biopsy safe for in vitro matured oocytes?

INTRODUCTION

Preconception diagnosis requires first polar body biopsy. When the hole in the zona pellucida is made with a laser beam, heat propagation could, like the biopsy itself, be deleterious. Our aim was to evaluate the effect of this technique on human in vitro matured oocyte and embryo development.

METHODS

One hunded fifty five retrieved immature oocytes from 75 women, matured in vitro, were distributed in 3 groups: 50 oocytes in a control group, without laser drilling and first polar body biopsy, 52 oocytes in a group with only laser drilling, and 53 oocytes in a group with both laser drilling and first polar body biopsy. Safety was evaluated using four criteria: [1] oocyte lysis rate, [2] oocyte activation rate, [3] oocyte development after calcium ionophore treatment, [4] and embryo chromosome breakage incidence after Tarkowski preparation.

RESULTS

No difference in the four criteria was observed between the 3 oocyte groups.

CONCLUSIONS

We did not find evidence of deleterious effect of laser drilling and first polar body biopsy on in vitro matured oocytes, according to our criteria.

Role of Preimplantation Genetic Diagnosis (PGD) in Current Infertility Practice

Chromosome imbalances are the leading cause of pregnancy loss in humans and play major roles in male and female infertility. Within the past two decades, the development and application of preimplantation genetic diagnosis (PGD) has played an important role in infertility practices worldwide. The purpose of this review is to discuss, how PGD may be applied in combating numerical chromosomal abnormalities and in Robertsonian and reciprocal chromosome translocations. We shall consider prevalence and risk of each aberration, interchromosomal effects and rationale behind use of PGD in each case. Numerical chromosome abnormalities (aneuploidy and polyploidy) in particular affect a very high proportion of preimplantation embryos (~ 50%). Given that a majority of preimplantation embryos are aneuploid, PGD can be used to screen embryos and transfer euploid embryos to improve pregnancy rates and reduce spontaneous abortions. The rationale of utilize PGD to transfer only euploid embryos would seem sound, but controversies exist surrounding application of PGD for aneuploidy detection. To this end, we will discuss the dichotomy between favorable descriptive reports and less favorable randomized clinical trial data. This review will discuss the trend towards differing sources of embryonic DNA (e.g. polar body vs blastomere vs blastocyst) as well as development of novel technologies for 24 chromosomes analysis.

The role of preimplantation genetic diagnosis in diagnosing embryo aneuploidy

PURPOSE OF REVIEW

Use of preimplantation genetic diagnosis to improve in-vitro fertilization outcomes is reviewed.

RECENT FINDINGS

Many embryos produced in vitro contain chromosomal abnormalities and have little potential for forming a viable pregnancy. The most commonly used method for preimplantation genetic diagnosis involves embryo biopsy on day 3 of development, followed by fluorescence in-situ hybridization analysis of 5-12 chromosomes. However, positive results have been more common with single-cell biopsy and the analysis of nine or more chromosomes, including 15, 16, 21, and 22. Comparative genomic hybridization, array-comparative genomic hybridization, and single-nucleotide polymorphism arrays analyze all chromosomes and, although technically demanding and requiring experience for successful use, improve the selection potential of preimplantation genetic diagnosis and minimize error rates. Recent data suggest that biopsy at the blastocyst stage may allow sampling of representative genetic material without compromising embryo viability. The optimal strategy for aneuploidy screening using preimplantation genetic diagnosis seems to be blastocyst biopsy at 5 days and comprehensive chromosome analysis (comparative genomic hybridization, array-comparative genomic hybridization, single-nucleotide polymorphism array).

SUMMARY

The use of preimplantation genetic diagnosis to assist the identification and preferential transfer of healthy euploid embryos should improve implantation rates, reduce miscarriages and trisomic offspring, and ultimately lead to an increase in live birth rates.

Technology requirements for preimplantation genetic diagnosis to improve assisted reproduction outcomes

Preimplantation genetic diagnosis has been proposed as a method to improve assisted reproduction technology outcomes, but different techniques have produced conflicting results. The use of appropriate techniques may provide positive outcomes.

Successful pregnancies after application of array-comparative genomic hybridization in PGS-aneuploidy screening

Recurrent IVF failure, implantation failure and early embryo demise can be attributed to the high frequency of chromosomal aneuploidy observed in human embryos. Preimplantation genetic screening (PGS) using multiple displacement amplifications (MDA) and array comparative genomic hybridization (aCGH) was successfully performed on eight patients with a minimum of seven recurrent IVF failures with the aim of detecting aneuploidy and ameliorating pregnancy rate. A total of 41 embryos with eight or more cells were biopsied by taking two blastomeres from each embryo. The DNA from these blastomeres were amplified and analysed by aCGH technology. The aCGH results showed a complex panel of chromosomal abnormalities in 60% of the diagnosed embryos. Some abnormalities could not be detected by the seven-probe panel (13, 16, 18, 21, 22, X and Y) used in fluorescence in-situ hybridization. Six out of eight patients had embryos for transfer with five out of those six showing positive pregnancy tests. As far as is known, this report is the first to show a pregnancy after PGS using the aCGH technology. The pregnancy rate obtained here is encouraging and will open the door for enrollment of more patients.

Male gamete survival at stake: causes and solutions

Over the years, the development of assisted reproductive technology to bypass male factor infertility has improved drastically. Considered one of the most perplexing disorders in the reproductive field, male factor infertility is prevalent and may be on the rise. Unfortunately, its aetiology remains elusive. One of the main reasons lies in the complex machinery and structure of the hydrodynamic sperm cell. Its polyunsaturated fatty acid cell membrane, the protamines in its genetic material and the absence of antioxidants in its cytoplasm ensure that the spermatozoon is highly susceptible to environmental effects. The spermatozoon's genesis, storage, and transport through the male reproductive tract are also susceptible, genetically and pathologically, to environmental effects. This review aims to include all the possible causes of disruption to this unique cell and their probable solutions, in the hope of clearing up the ambiguity that surrounds male factor infertility.

Preimplantation genetic screening: a survey of in vitro fertilization clinics

PURPOSE

The purpose of this study was to determine which US in vitro fertilization clinics provide preimplantation genetic screening for aneuploidy in treating infertility, and to explore clinic directors' attitudes toward this technique.

METHODS

Online survey included 415 US assisted reproductive technology clinics. The survey had a valid response rate of 45% or 186 clinics.

RESULTS

Nearly 68% of US in vitro fertilization clinics responding to the survey provided preimplantation genetic screening in an effort to increase success rates of fertility treatment. More than half of these in vitro fertilization clinics (56%) provided preimplantation genetic screening for advanced maternal age and the same percentage provided preimplantation genetic screening to treat repeated in vitro fertilization failure, whereas 66% provided preimplantation genetic screening to treat women with repeated miscarriage. Opinions of the effectiveness of preimplantation genetic screening for these indications varied widely, even among those providing it. Most directors (85%) of clinics providing preimplantation genetic screening believed that more data are needed to determine whether and to whom it should be offered.

CONCLUSIONS

Despite the lack of data supporting the use of preimplantation genetic screening for recurrent pregnancy loss, in vitro fertilization failure, and advanced maternal age, a majority of in vitro fertilization clinics in the United States offer preimplantation genetic screening for these purposes. There is significant support among clinic directors for more research into the effectiveness of preimplantation genetic screening and for professional guidelines in this area.

Hybridization of the 18 alpha-satellite probe to chromosome 1 revealed in PGD

Although the chromosome 18 alpha-satellite probe is considered to have a very low polymorphism rate, the routine use of this probe in prenatal diagnosis revealed rare variants in size and copy number of these sequences. A polymorphic signal was detected in preimplantation genetic diagnosis (PGD) for aneuploidy, in a patient with repeated early miscarriages. A third small signal of chromosome 18 alpha-satellite probe was observed in two of four evaluated embryos. Hybridization to the woman's metaphasic lymphocytes revealed that the small signal was localized in the pericentromeric region of chromosome 1. Reanalysis of blastomeres with telomeric probes for chromosome 18q confirmed the presence of only two copies of chromosome 18. Options for verifying PGD analysis results, to prevent misdiagnosis in cases of suspected polymorphism, are discussed. Although some authors speculate about a possible role of heterochromatin polymorphism in infertility, this rare polymorphism of 18 alpha-satellite sequences is in itself probably a normal variant. This is the third report of a cross-hybridization of the chromosome 18 alpha-satellite probe and the first report of the localization of the polymorphic 18 alpha-satellite signal to chromosome 1.

Gamete cytogenetic study in couples with implantation failure: aneuploidy rate is increased in both couple members

PURPOSE

Implantation failure is known to be associated with an increased risk of aneuploidy in embryos, a situation leading to a pre-implantation genetic screening, not allowed in different countries like France. Our aim was to evaluate the gamete aneuploidy incidence in this context, using first polar body and spermatozoa aneuploidy screening.

METHODS

Three groups were considered: 11 couples with pregnancy obtained after IVF for female infertility (group 1); 20 couples with pregnancy obtained after IVF for male infertility (group 2); and 35 couples with implantation failure (group 3). In group 3, 28 couples treated by ICSI volunteered for first polar body analysis (PB1).

RESULTS

Spermatozoa aneuploidy rate was increased in groups 2 (1.6%) and 3 (2.1%) in comparison to group 1 (0.6%). PB1 aneuploidy rate was 35.4% in group 3. Finally, eight couples (32%) had no particular chromosomal risk in gametes, 15/25 (60%) presented an increased spermatic (>2%) or oocyte (>1/3) aneuploidy rate, and 2/25 (8%) had both.

CONCLUSION

Those results confirm that implantation failure has a heterogeneous origin, that gamete chromosome abnormality rate is one of the major contributing factors, and that 1st Polar body and spermatozoa aneuploidy screening or pre-implantation genetics screening may be indicated for these couples.

Multicentre trial of preimplantation genetic screening reported in the New England Journal of Medicine: an in-depth look at the findings

A randomized clinical trial of 406 patients with advanced maternal age by Mastenbroek and co-workers recently published in the New England Journal of Medicine showed a significant decrease in pregnancy outcome after preimplantation genetic screening (PGS). It is our opinion that this study suffers from a number of insurmountable inaccuracies and that these are either a direct consequence of the inexperience of the team or of a general disregard of vital guidelines reported in the literature. Most importantly, the authors show that in their hands embryo biopsy may affect as many as half the embryos. The error rate was not presented, shedding doubt on the authors' abilities to reliably diagnose the biopsied cells. An evaluation of the study indicates that poor biopsy technique, sub standard fixation and FISH methods, poor IVF outcomes and inappropriate patient selection are the cause of the discouraging results obtained by these authors rather than problems inherent to PGS.

Role of aneuploidy on embryo implantation

Approximately 30% of oocytes in the human species carry a chromosomal imbalance. This condition has severe clinical consequences as approximately one-third of spontaneous abortions are aneuploid. The most obvious link to the increase of aneuploidy in oocytes is maternal age. This has been directly confirmed by the analysis of polar bodies. Their analysis permits to give confirmation of the high predisposition of oocytes to meiotic errors. Also, the study of chromosomes on sperm has revealed a frequency of 6-7% aneuploidy in normal sperm samples, and is significantly increased in cases of severe oligoasthenoteratospermia or azoospermia due to testicular failure. During the preimplantation period there is a progressive loss of abnormal embryos at specific stages in early development, through growth arrest and degeneration of abnormal embryos. The frequency of chromosomal abnormalities is strictly related to the category of patients (advanced maternal age, repeated cycles, altered karyotype, repeated miscarriages, TESE). Based on these considerations, preimplantation genetic diagnosis for aneuploidy is proposed in reproductive medicine with the finality of improving the clinical outcome after IVF. Substantial evidence has been accumulated on the positive impact of the technique, reporting increased implantation rates and a concomitant decrease of spontaneous abortions and trisomic pregnancies.

Discordance among blastomeres renders preimplantation genetic diagnosis for aneuploidy ineffective

PURPOSE

To investigate the contribution of discordance among blastomeres from the same embryo in the interpretation of blastomeres biopsied from day 3 embryos.

METHODS

228 IVF embryos had two blastomeres removed and fluorescent in situ hybridization (FISH) was used to detect aneuploidy of chromosomes 13, 15, 16, 18, 21, 22, X and Y. Of the 228 embryos, 102 had complete FISH results for both blastomeres.

RESULTS

When the 2 blastomeres of 102 embryos with successful FISH results were compared, 26 (25.5%) were concordant for all 8 chromosomes and 76 (74.5%) were discordant for one or more chromosomes. Among the 102 embryos, 12 (12%) were disomy in both blastomeres and 37 (36%) were disomic in all 8 chromosomes in one of the two blastomeres.

CONCLUSION

Discordance among blastomeres from the same embryo appears to present a significant problem in interpreting results of embryos biopsied on day 3 and analyzed by FISH especially when most PGD's are done on single blastomeres.

Cytogenetic analysis and developmental assessment of mouse embryos derived from in vitro fertilization of oocytes reconstructed by meiosis-II chromosome transplantation

An electrofusion methodology for transferring meiosis-II chromosomes (M-II-t) has not been completely established. The present study compared the use of two temperatures (fusion at 37 C for Group A and 25 C for Group B) during an electrofusion procedure for mouse oocyte M-II-t and investigated the cytogenetic normality and developmental competence of embryos derived from in vitro fertilization using oocytes reconstructed by M-II-t. The M-II-t oocytes were fertilized in vitro and cultured to the blastocyst stage; the resultant embryos were analyzed cytogenetically. Subsequently, chromosomal normality of the resultant embryos at the prometaphase stage of first cleavage division and the integrity of the meiosis-II spindles of the reconstructed oocytes were analyzed. The success rate of electrofusion in Group B was 92.1%, which was significantly different from that in Group A (49.2%) (P<0.05). The fertilization rates (A, 80.7%; B, 77.2%) and development rates (A, 70.9%; B, 65.5%) in the M-II-t groups were significantly lower than those in the control group (95.0 and 92.2%, respectively) (P<0.05). The incidence of chromosomal abnormalities in the Group A embryos (20.5%) at the blastocyst stage was significantly higher than that in the control group embryos (8.5%) (P<0.05), but the incidence of chromosomal abnormalities in Group B (12.5%) was not significantly different compared with the other groups. A temperature of 25 C during the electrofusion procedure for M-II-t resulted in a good fusion rate, good development rate, and efficient production of chromosomally normal blastocysts. Furthermore, the incidence of chromosomal abnormalities in the first cleavage embryos at the prometaphase stage in Group B (9.6%) did not differ significantly from that in the control group (6.6%). The spindle morphology of the M-II-t oocytes in Group B was normal.

Embryo morphology and development are dependent on the chromosomal complement

OBJECTIVE

To analyze embryo morphology in relation to the corresponding chromosomal status, in order to evaluate the effects of aneuploidy over fragmentation, delayed cleavage, and arrested cleavage.

DESIGN

Retrospective study.

SETTING

Reproductive Medicine Unit, Società Italiana di Studi di Medicina della Riproduzione, Bologna, Italy.

PATIENT(S)

A total of 662 patients with a poor prognosis for pregnancy underwent 916 cycles of preimplantation genetic diagnosis for aneuploidy.

INTERVENTION(S)

The chromosomes XY, 13, 15, 16, 18, 21, and 22 were analyzed in blastomeres biopsied from day 3 embryos.

MAIN OUTCOME MEASURE(S)

Embryo morphology, chromosomal status of the analyzed blastomeres, and spreading and reanalysis of nontransferred embryos.

RESULT(S)

The incidence of chromosomal abnormalities was significantly higher in arrested or slow-cleaving embryos, and in embryos cleaving too fast, compared to embryos with eight cells at 62 hours after insemination. The presence of an uneven number of blastomeres or fragments scattered in the perivitelline space was associated with an increased incidence of chromosomal abnormalities.

CONCLUSION(S)

A correlation between embryo development and chromosomal complement makes the incidence of chromosomal abnormalities significantly higher in embryos dividing according to a time frame and a symmetry plan which are different from what are expected. The type of fragmentation is also related to chromosomal status, which explains why the extrusion of fragments might severely affect embryo viability.