The current status of preimplantation genetic screening: British Fertility Society Policy and Practice Guidelines

Noninvasive amino acid turnover predicts human embryo aneuploidy

Assisted reproduction technology has two significant problems: low success rates and multiple pregnancies. Because of these problems, the priority in IVF clinics is to develop a potential diagnostic test that can be used to select the embryos with the ultimate developmental competence. Aneuploidy screening as embryo selection criteria will ensure that the transferred embryos are euploid and high implantation rate. We hypothesize that aneuploidy in human preimplantation embryos could be discriminated by their amino acid metabolism profile in the spent culture media. Preimplantation genetic testing for aneuploidy results and spent embryo culture medium amino acid content were analyzed for 58 couples. The next-generation sequencing technique was used and coupled with TE biopsy. Forty euploid and 71 aneuploid blastocysts were evaluated. Embryos were cultured individually until day 5 or 6 of embryo development. Spent culture medium was collected after finishing the culture. There was no statistical difference between D3 and D5 embryo morphology between euploid and aneuploid embryos (p > .05). Eight amino acids, including SER, GLY, HIS, ARG, THR, ALA, PRO, and TYR, were detected in the culture medium from the blank control group, euploid group, and aneuploid group. Only TYR amino acid concentration was found significantly higher in the aneuploid group compared to the euploid group (p < .003). Tyrosine amino acid levels equal to and above 76.38 µmol/L could be considered aneuploid. Aneuploid embryos demonstrate altered amino acid turnover in vitro relative to euploid counterparts. A noninvasive method of amino acid profiling will be of value as a tool for routine preimplantation embryo selection among all patient groups.

Is there still a rationale for non-invasive PGT-A by analysis of cell-free DNA released by human embryos into culture medium?

Human embryos utilise an array of processes to eliminate the very high prevalence of aneuploid cells in early embryo stages. Human embryo self-correction was recently demonstrated by their ability to eliminate/expel abnormal blastomeres as cell debris/fragments. A whole genome amplification study has demonstrated that 63.6% of blastocysts expelled cell debris with abnormal chromosomal rearrangements. Moreover, 55.5% of euploid blastocysts expel aneuploid debris, strongly suggesting that the primary source of cell free DNA in culture media is expelled aneuploid blastomeres and/or their fragments. Such a substantial ability to self-correct downstream from the blastocyststage, therefore, renders any chromosomal diagnosis at the blastocyststage potentially useless, and this, unfortunately, also must particularly include non-invasive PGT-A based on cell-free DNA in spent medium. High rates of false-positive diagnoses of human embryos often lead to non-use and/or disposal of embryos with entirely normal pregnancy potential. Before adopting yet another round of unvalidated PGT-A as a routine adjunct to IVF, we here present facts that deserve to be considered.

Preconception tests at advanced maternal age

Pregnancies at an advanced reproductive age are increasingly common. However, the safety of pregnancy remains a concern as maternal age is a recognized independent factor for various obstetric complications. Also, age is a risk factor for most systematic health problems and older women are more likely to enter into pregnancy with pre-existing conditions. At the moment there is no separate, structured guidance on preconception tests at advanced maternal age. However, the preconceptual period offers an ideal window to recognize and address underlying health issues, social issues and harmful lifestyle behaviours in order to optimize maternal health ultimately reducing infertility, perinatal morbidity and mortality. Preconception tests should be clinically relevant aiming to identify risk factors and address them to predict and prevent infertility and pregnancy complications. The importance of preconception care is magnified for women of advanced age for whom the risks are higher and the potential benefits greater.

Preimplantation Genetic Testing for Aneuploidy: A Review

Importance

Preimplantation genetic testing for aneuploidy (PGT-A) has undergone many technical developments over recent years, including changes in biopsy timings, methodology, and genetic analysis techniques. The evidence surrounding the efficaciousness of PGT-A is sporadic and inconsistent; as such, significant doubt and concern remain regarding its widespread implementation.

Objective

This review seeks to describe the historical development of PGT-A and to analyze and summarize the current published literature.

Conclusions

At times during its infancy, PGT-A failed to display conclusive improvements in results; with newer technologies, PGT-A appears to yield superior outcomes, including reductions in miscarriages and multiple gestations. Clinicians and patients should assess the use of PGT-A on a case-by-case basis, with laboratories encouraged to utilize blastocyst biopsy and next-generation sequencing when conducting PGT-A. Further studies providing cumulative live birth rates and time to live birth are required if PGT-A is to be proven as producing superior outcomes.

Relevance

PGT-A has the potential ability to impact in vitro fertilization success rates, and as it is increasingly adopted worldwide, it is crucial that clinicians are aware of the evidence for its continued use.

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.

Developmental outcome of 9-year-old children born after PGS: follow-up of a randomized trial

STUDY QUESTION

Does Day-3 cleavage-stage PGS affect neurodevelopment of 9-year-old IVF offspring?

SUMMARY ANSWER

We did not find evidence of adverse consequences of Day-3 cleavage-stage PGS on neurodevelopment of 9-year-old IVF offspring, although children born after IVF with or without PGS often had a non-optimal neurological condition.

WHAT IS KNOWN ALREADY

Knowledge on long-term sequelae for development and health of children born following PGS is lacking. This is striking as evidence accumulates that IVF itself is associated with increased risk for impaired health and development in the offspring.

STUDY DESIGN SIZE, DURATION

This prospective, assessor-blinded, multicentre, follow-up study evaluated development and health of 9-year-old IVF children born to women who were randomly assigned to IVF with PGS (PGS group) or without PGS (control group). The follow-up examination at 9 years took place between March 2014 and May 2016.

PARTICIPANTS/MATERIALS, SETTING, METHODS

In total, 408 women were included and randomly assigned to IVF with or without Day-3 cleavage-stage PGS. This resulted in 52 ongoing pregnancies in the PGS group and 74 in the control group. In the PGS group, 59 children were born alive; in the control group, 85 children were born alive. At the age of 9 years, 43 children born after PGS and 56 control children participated in the study. Our primary outcome was the neurological optimality score, a sensitive measure of neurological condition assessed with a standardized, age-specific test (Touwen test). Secondary outcomes were adverse neurological condition (neurologically abnormal and the complex form of minor neurological dysfunction), cognitive development (intelligence quotient and specific domains), behaviour (parental and teacher's questionnaires), blood pressure and anthropometrics.

MAIN RESULTS AND THE ROLE OF CHANCE

Neurodevelopmental outcome of PGS children did not differ from that of controls; the neurological optimality scores (mean values [(95% CI]: PGS children 51.5 [49.3; 53.7], control children 53.1 [50.5; 55.7]) were not significantly different. The prevalences of adverse neurological outcome (in all but one child implying the presence of the complex form of minor neurological dysfunction) did not differ between the groups (PGS group 17/43 [40%], control group 19/56 [34%]), although the prevalence of complex minor neurological dysfunction in both groups was rather high. Also intelligence quotient scores of the two groups were not significantly different (PGS group 114 [108; 120]); control group 117 [109; 125]), and the behaviour, blood pressure and anthropometrics of both groups did not differ. Mean blood pressures of both groups were above the 60th percentile.

LIMITATIONS REASONS FOR CAUTION

The power analysis of the study was not based on the number of children needed for the follow-up study, but on the number of women who were needed to detect an increase in ongoing pregnancy rates after PGS. In addition, our study evaluated embryo biopsy in the form of PGS at cleavage stage (Day-3 embryo biopsy), while currently PGS at blastocyst stage (Day-5 embryo biopsy) is recommended and increasingly being used.

WIDER IMPLICATIONS OF THE FINDINGS

Our findings indicate that PGS in cleavage stage embryos is not associated with adverse effects on neurological, cognitive and behavioural development, blood pressure and anthropometrics of offspring at 9 years. This is a reassuring finding as embryo biopsy in the forms of PGS and PGD is increasingly applied. However, both groups of IVF offspring showed high prevalences of the clinically relevant form of minor neurological dysfunction, which is a point of concern for the IVF community. In addition, our study confirms findings of others that IVF offspring may be at risk of an unfavourable cardiovascular outcome. These findings are alarming and highlight the importance of research on the underlying mechanisms of unfavourable neurodevelopmental and cardiovascular outcomes in IVF offspring.

STUDY FUNDING/COMPETING INTEREST(S)

The randomized controlled trial was financially supported by the Organization for Health Research and Development (ZonMw), The Netherlands (Grant number 945-03-013). The follow-up was financially supported by the University Medical Center Groningen (Grant number: 754510), the Cornelia Foundation, and the graduate schools BCN and Share, Groningen, The Netherlands. The sponsors of the study had no role in study design, data collection, data analysis, data interpretation or writing of the report. There are no conflicts of interest.

TRIAL REGISTRATION NUMBER

ISRCTN76355836.

Preimplantation genetic screening

Preimplantation genetic diagnosis was first successfully performed in 1989 as an alternative to prenatal diagnosis for couples at risk of transmitting a genetic or chromosomal abnormality, such as cystic fibrosis, to their child. From embryos generated in vitro, biopsied cells are genetically tested. From the mid-1990s, this technology has been employed as an embryo selection tool for patients undergoing in vitro fertilisation, screening as many chromosomes as possible, in the hope that selecting chromosomally normal embryos will lead to higher implantation and decreased miscarriage rates. This procedure, preimplantation genetic screening, was initially performed using fluorescent in situ hybridisation, but 11 randomised controlled trials of screening using this technique showed no improvement in in vitro fertilisation delivery rates. Progress in genetic testing has led to the introduction of array comparative genomic hybridisation, quantitative polymerase chain reaction, and next generation sequencing for preimplantation genetic screening, and three small randomised controlled trials of preimplantation genetic screening using these new techniques indicate a modest benefit. Other trials are still in progress but, regardless of their results, preimplantation genetic screening is now being offered globally. In the near future, it is likely that sequencing will be used to screen the full genetic code of the embryo.

Preimplantation genetic screening- the required RCT that has not yet been carried out

The utilization of trophectoderm biopsy combined with comprehensive chromosome screening (CCS) tests for embryonic aneuploidy was recently suggested to improve IVF outcome, however, not without criticisms. The ongoing discussion on the unrestricted clinical adoption of preimplantation genetic screening (PGS) has called for a proper randomized controlled trial (RCT), aiming to further evaluate the cumulative live birth rates (LBRs) following a single oocyte retrieval, utilizing all fresh and frozen embryos. Since this study seems not to appear for various reasons, we present herewith, the hypothetical required RCT based on the hitherto published literature.After implementing data from the hitherto published literature on blastulation and aneuploidy rates, the rate of mosaicism and technical errors and implantation rates/LBRs of non-PGS day-3 and blastocyst and PGS blastocyst, we could clearly demonstrate the superiority of non-PGS embryo (day-3 and blastocyst) transfer over PGS blastocyst transfer, in terms of cumulative LBR (18.2-50 % vs 7.6-12.6 %, respectively).We therefore believe that until the proper, non-hypothetical RCT on the efficacy of this procedure will appear, PGS should be offered only under study conditions, and with appropriate informed consents.

Should pre-implantation genetic screening be implemented to routine clinical practice?

The utilization of trophectoderm biopsy combined with comprehensive chromosome screening (CCS) tests for embryonic aneuploidy was recently suggested to improve IVF outcome, however, not without criticisms. Since mosaicism has been reported in as high as 90% of blastocyst-stage embryos, we aimed to evaluate the accuracy of trophectoderm multiple biopsies using next-generation sequencing (NGS). Eight top quality blastocysts underwent three trophectoderm biopsies each, followed by NGS. In four blastocysts, the rest of the embryo, which included the inner cell mass, was also analyzed. Five of the 24 (20.8%) trophectoderm biopsies revealed inconclusive results, while 4 (16.6%) demonstrated embryonic mosaicism. Overall, 10 (35.7%) of the 28 (24 trophectoderms and 4 inner cell masses) biopsies revealed mosaicism or inconclusive results. Our preliminary observations contribute to the ongoing discussion on the unrestricted clinical adoption of PGS, suggesting, that until proper evaluation of its effectiveness and cost-effectiveness will be provided, PGS should be offered only under study conditions, and with appropriate informed consents.

Omics in Reproductive Medicine: Application of Novel Technologies to Improve the IVF Success Rate

Treatment for many infertile couples often consists of in vitro fertilization (IVF) but an estimated 70% of IVF cycles fail to produce a live birth. In an attempt to improve the live birth rate, the vast majority of IVF cycles performed in the United States involve the transfer of multiple embryos, a practice that increases the risk of multiple gestation pregnancy. This is a concern because multiple gestation pregnancies are associated with an increased incidence of maternal and fetal complications and significant cost associated with the care of preterm infants. As the ideal outcome of each IVF cycle is the birth of a single healthy baby, significant effort has focused on identifying embryos with the greatest developmental potential. To date, selection of euploid embryos using comprehensive chromosome screening (CCS) is the most promising approach while metabolomic and proteomic assessment of spent culture medium have the potential to noninvasively assess embryo viability. Endometrial gene expression profiling may help determine the optimal time to perform embryo transfer. While CCS has been implemented in some clinics, further development and optimization will be required before analysis of spent culture medium and endometrial gene expression profiling make the transition to clinical use. This review will describe efforts to identify embryos with the greatest potential to result in a healthy, live birth, with a particular emphasis on detection of embryo aneuploidy and metabolic profiling of spent embryo culture medium. Assessment of endometrial receptivity to identify the optimal time to perform embryo transfer will also be discussed.

Preimplantation genetic screening (PGS) still in search of a clinical application: a systematic review

Only a few years ago the American Society of Assisted Reproductive Medicine (ASRM), the European Society for Human Reproduction and Embryology (ESHRE) and the British Fertility Society declared preimplantation genetic screening (PGS#1) ineffective in improving in vitro fertilization (IVF) pregnancy rates and in reducing miscarriage rates. A presumably upgraded form of the procedure (PGS#2) has recently been reintroduced, and is here assessed in a systematic review. PGS#2 in comparison to PGS#1 is characterized by: (i) trophectoderm biopsy on day 5/6 embryos in place of day-3 embryo biopsy; and (ii) fluorescence in-situ hybridization (FISH) of limited chromosome numbers is replaced by techniques, allowing aneuploidy assessments of all 24 chromosome pairs. Reviewing the literature, we were unable to identify properly conducted prospective clinical trials in which IVF outcomes were assessed based on "intent to treat". Whether PGS#2 improves IVF outcomes can, therefore, not be determined. Reassessments of data, alleged to support the efficacy of PGS#2, indeed, suggest the opposite. Like with PGS#1, the introduction of PGS#2 into unrestricted IVF practice again appears premature, and threatens to repeat the PGS#1 experience, when thousands of women experienced reductions in IVF pregnancy chances, while expecting improvements. PGS#2 is an unproven and still experimental procedure, which, until evidence suggests otherwise, should only be offered under study conditions, and with appropriate informed consents.

Comprehensive embryo testing. Experts' opinions regarding future directions: an expert panel study on comprehensive embryo testing

STUDY QUESTION

What do scientists in the field of preimplantation genetic diagnosis (PGD) and preimplantation genetic screening (PGS) consider to be the future direction of comprehensive embryo testing?

SUMMARY ANSWER

Although there are many biological and technical limitations, as well as uncertainties regarding the meaning of genetic variation, comprehensive embryo testing will impact the IVF/PGD practice and a timely ethical reflection is needed.

WHAT IS KNOWN ALREADY

Comprehensive testing using microarrays is currently being introduced in the context of PGD and PGS, and it is to be expected that whole-genome sequencing will also follow. Current ethical and empirical sociological research on embryo testing focuses on PGD as it is practiced now. However, empirical research and systematic reflection regarding the impact of comprehensive techniques for embryo testing is missing.

STUDY DESIGN, SIZE AND DURATION

In order to understand the potential of this technology and to be able to adequately foresee its implications, we held an expert panel with seven pioneers in PGD.

PARTICIPANTS/MATERIALS, SETTING, METHODS

We conducted an expert panel in October 2011 with seven PGD pioneers from Belgium, The Netherlands, Germany and the UK.

MAIN RESULTS AND THE ROLE OF CHANCE

Participants expected the use of comprehensive techniques in the context of PGD. However, the introduction of these techniques in embryo testing requires timely ethical reflection as it involves a shift from choosing an embryo without a particular genetic disease (i.e. PGD) or most likely to result in a successful pregnancy (i.e. PGS) to choosing the best embryo based on a much wider set of criteria. Such ethical reflection should take account of current technical and biological limitations and also of current uncertainties with regard to the meaning of genetic variance. However, ethicists should also not be afraid to look into the future. There was a general agreement that embryo testing will be increasingly preceded by comprehensive preconception screening, thus enabling smart combinations of genetic testing.

LIMITATIONS, REASONS FOR CAUTION

The group was composed of seven participants from four Western Europe countries. As willingness to participate in this study may be connected with expectations regarding the pace and direction of future developments, selection bias cannot be excluded.

WIDER IMPLICATIONS OF THE FINDINGS

The introduction of comprehensive screening techniques in embryo testing calls for further ethical reflection that is grounded in empirical work. Specifically, there is a need for studies querying the opinions of infertile couples undergoing IVF/PGS regarding the desirability of embryo screening beyond aneuploidy.

STUDY FUNDING/COMPETING INTEREST(S)

This research was supported by the CSG, Centre for Society and Life Sciences (project number: 70.1.074). The authors declare no conflict of interest.

TRIAL REGISTRATION NUMBER

N/A.

A review of, and commentary on, the ongoing second clinical introduction of preimplantation genetic screening (PGS) to routine IVF practice

PURPOSE

Current re-introduction of "improved" preimplantation genetic screening (PGS#2) raises the question whether PGS#2 is ready for routine clinical application.

METHODS

We assessed available evidence via review of published data for years 2005-2012, and review of currently ongoing registered clinical trials, based on searches under appropriate key words in PubMed, MEDLINE, Cochrane Database System Review and Google Scholar and http://www.ClinicalTrials.gov . In absence of prospective clinical trials, and due to limited available data, individual publications/ongoing studies are assessed.

RESULTS

PGS#2 offers significant improvements in accuracy of aneuploidy diagnosis over PGS#1. By moving embryo biopsy from day-3 after fertilization (6-8 cell stage) to trophectoderm biopsy at blastocyst stage (day 5-6), PGS#2, however, adds additional co-variables to the analysis of efficacy of the procedure, which have special relevance for women with diminished ovarian reserve (DOR), who usually produce small egg and embryo numbers. Limited published data, claiming efficacy of PGS#2, as well as ongoing clinical trials, do not consider these additional co-variables, do not analyze outcomes by intent to treat and, therefore, have to be considered biased in patient selection.

CONCLUSIONS

Here reached conclusions are based on absence of adequate data rather than affirmative outcome assessments. They, therefore, are subject to change at any future date with generation of significant new data. Premature introduction of PGS#1 caused significant damage to patients. As currently no reliable PGS#2 data are available to suggest improvements in IVF outcomes, to avoid a repeat of the PGS#1 experience, PGS#2 should be considered experimental until data show otherwise.

Lessons from elective in vitro fertilization (IVF) in, principally, non-infertile women

BACKGROUND

We here report the first investigation of exclusively elective in vitro fertilization (IVF) cycles in women with no apparent history of infertility. Since IVF outcome in women with infertility are always influenced by underlying causes of infertility, a study on non-infertile women may offer new insights.

METHODS

We investigated 88 females without history of infertility in 109 consecutive elective IVF cycles, almost exclusively performed for purposes of preimplantation genetic screening (PGS; i.e., elective gender selection). The following questions were addressed: (i) impact of PGS on IVF pregnancy chances; (ii) impact of transfer of 1 vs. ≥2 embryos on IVF pregnancy chances; (iii) correlation of anti-Müllerian hormone (AMH) levels to embryo ploidy (iv) effect of gonadotropin dosage used in stimulation on available embryos for transfer; and (v) in form of a 1:1 case control study, compared 33 elective PGS cycles with matched control cycles without PGS, performed in couples with either prior tubal ligations and/or severe male factor infertility as indication of IVF.

RESULTS

The overall clinical pregnancy rate for the group was 36.7%; pregnancy was associated with number of euploid (P = 0.009) and number of embryos transferred (P = 0.001). Odds of pregnancy were 3.4-times higher if ≥4 euploid embryos were produced in comparison to <4 (95% CI 1.2 to 9.2; P = 0.019), and odds of pregnancy were 6.6-times higher if greater than or equal to 2 rather than <1 euploid embryos were transferred (95% CI 2.0 to 21.7; P = 0.002). Increasing AMH (P = 0.001) and gonadotropin dosage used in ovarian stimulation (P = 0.024), was, independently, associated with number of available euploid embryos. Increasing AMH, but not follicle stimulating hormone (FSH), was associated with number of embryos available for biopsy and PGS (P = 0.0001). Implantation rates were 26.4% with PGS and 9.5% without (P = 0.008). Women undergoing PGS, demonstrated 4.58-times higher odds of pregnancy than matched controls (95% CI 1.102 to 19.060, Exp 4.584, P = 0.036).

CONCLUSIONS

This study suggests that outcomes of elective IVF cycles may significantly deviate from infertility-associated cycles. Affirming proof of concept for PGS, utilizing day-3 embryo biopsy and fluorescence in-situ hybridization (FISH), both widely held responsible for earlier failures to establish such proof, suggests that the principal cause of prior failures were likely not insufficient laboratory techniques but poor patient selection for PGS. Such a conclusion questions the current reintroduction of PGS with improved techniques and technologies in absence of prior determination of suited patient populations.

Polar body array CGH for prediction of the status of the corresponding oocyte. Part I: clinical results

BACKGROUND

Several randomized controlled trials have not shown a benefit from preimplantation genetic screening (PGS) biopsy of cleavage-stage embryos and assessment of up to 10 chromosomes for aneuploidy. Therefore, a proof-of-principle study was planned to determine the reliability of alternative form of PGS, i.e. PGS by polar body (PB) biopsy, with whole genome amplification and microarray-based comparative genomic hybridization (array CGH) analysis.

METHODS

In two centres, all mature metaphase II oocytes from patients who consented to the study were fertilized by ICSI. The first and second PBs (PB1and PB2) were biopsied and analysed separately for chromosome copy number by array CGH. If either or both of the PBs were found to be aneuploid, the corresponding zygote was then also processed by array CGH for concordance analysis.

RESULTS

Both PBs were biopsied from a total of 226 zygotes from 42 cycles (average 5.5 per cycle; range 1-15) in 41 couples with an average maternal age of 40.0 years. Of these, the ploidy status of the zygote could be predicted in 195 (86%): 55 were euploid (28%) and 140 were aneuploid (72%). With only one exception, there was at least one predicted aneuploid zygote in each cycle and in 19 out of 42 cycles (45%), all zygotes were predicted to be aneuploid. Fresh embryos were transferred in the remaining 23 cycles (55%), and one frozen transfer was done. Eight patients had a clinical pregnancy of which seven were evolutive (ongoing pregnancy rates: 17% per cycle and 30% per transfer). The ploidy status of 156 zygotes was successfully analysed by array CGH: 38 (24%) were euploid and 118 (76%) were aneuploid. In 138 cases complete information was available on both PBs and the corresponding zygotes. In 130 (94%), the ploidy status of the zygote was concordant with the ploidy status of the PBs and in 8 (6%), the results were discordant.

CONCLUSIONS

This proof-of-principle study indicates that the ploidy of the zygote can be predicted with acceptable accuracy by array CGH analysis of both PBs.

Genetic diagnostic methods for inherited eye diseases

Accurate molecular diagnosis of genetic eye diseases has proven to be of great importance because of the prognostic and therapeutic value of an accurate ascertainment of the underlying genetic mutation. Efforts continue in diagnostic laboratories to develop strategies that allow the discovery of responsible gene/mutations in the individual patient using the least number of assays and economizing on the expenses and time involved in the process. Once the ophthalmologist has made the best possible clinical diagnosis, blood samples are obtained for genetic testing. In this paper we will review the basic laboratory methods utilized to identify the chromosomal or mutational etiology of genetic diseases that affect the eye.

Does additional hybridization also improve preimplantation genetic screening results?

EVALUATION OF: Mir P, Rodrigo L, Mateu E et al. Improving FISH diagnosis for preimplantation genetic aneuploidy screening. Hum. Reprod. 25(7), 1812-1817 (2010). Mir et al. have evaluated the impact of additional hybridization rounds on FISH accuracy in preimplantation genetic screening (PGS) of aneuploidy. In a retrospective analysis of 1000 PGS cycles, embryo biopsy was performed on day 3. A greater number of embryos were diagnosed as chromosomally normal and were available for transfer after discarding 'false monosomies' and decreasing the number of noninformative embryos. The error rate for the FISH technique was 17.3% without and 5% with additional probes. A randomized controlled trial is needed to demonstrate improved clinical outcome. However, major obstacles in cleavage-stage PGS are chromosomal mosaicism and incomplete analysis. Therefore, polar body and/or trophectoderm analysis using 24 chromosome microarrays might be better alternatives.

Preimplantation genetic diagnosis: twenty years of practice

More than two decades after the first clinical application, preimplantation genetic diagnosis (PGD) is an established medical procedure and an accepted alternative to conventional prenatal diagnosis for patients at high risk of transmitting a genetic disorder to their offspring. The great advantage of PGD is that the diagnostic procedure is made already at the embryo stage, before transfer to the patient, and the need for pregnancy termination is thereby avoided. However, PGD can only be performed in connection with in-vitro fertilisation followed by embryo biopsy and genetic analysis of single cells, a complex and cumbersome procedure for both the couple as well as the professionals involved in the treatment. However, for couples at high risk of having an affected child, PGD may be the most attractive alternative to conceive unaffected children.

What is the role of assisted reproduction technology in the management of age-related infertility?

Although in the UK the upper age limit for National Health Service (NHS) provision of in vitro fertilisation (IVF) is 39 years of age there has been an increase in number of women having fertility treatment in their 40s. However, the success rates of IVF and intra-uterine insemination (IUI) in this group remain low. Human Fertilisation and Embryology Authority (HFEA) data from 2006 showed that the live-birth rate from IVF in the UK was 11% in the age group 40-42, 4.6% in the age group 43-44 and less than 4% in women over 44. We performed a literature search for studies using terms and combinations of terms in online databases and published meta-analyses reporting the outcome of interventions in older women. This review showed that assisted reproduction technologies (ARTs) continue to have low live-birth rates in women over 40. Trials showed that assisted hatching may increase the chance of pregnancy in women with poor history. Blastocyst transfer is associated with better outcome, whereas application of pre-implantation genetic screening (PGS) in older women has not increased the success rates. It appears that, with the exception of egg-donation, ART has no answer yet to age-related decline of female fertility.

Association between amino acid turnover and chromosome aneuploidy during human preimplantation embryo development in vitro

This study investigated the relationship between human preimplantation embryo metabolism and aneuploidy rates during development in vitro. One hundred and eighty-eight fresh and cryopreserved embryos from 59 patients (33.9 +/- 0.6 years) were cultured for 2-5 days. The turnover of 18 amino acids was measured in spent media by high-performance liquid chromatography. Embryos were either fixed for interphase fluorescent in situ hybridization analysis of chromosomes 13, 18, 19, 21, X or Y, or were assayed for mitochondrial activity. Amino acid turnover was different (P < 0.05) between stage-matched fresh and cryopreserved embryos due to blastomere loss following warming. The proportion of embryos with aneuploid cells increased as cell division progressed from pronucleate- (23%) to late cleavage stages (50-70%). Asparagine, glycine and valine turnover was significantly different between uniformly genetically normal and uniformly abnormal embryos on Days 2-3 of culture. By Days 3-4, the profiles of serine, leucine and lysine differed between uniformly euploid versus aneuploid embryos. Gender significantly (P < 0.05) affected the metabolism of tryptophan, leucine and asparagine by cleavage-stage embryos. Pronucleate zygotes had a significantly higher proportion of active:inactive mitochondria compared with cleavage-stage embryos. Furthermore, mitochondrial activity was correlated (P < 0.05) with altered aspartate and glutamine turnover. These results demonstrate the association between the metabolism, cytogenetic composition and health of human embryos in vitro.

Slow and ultrarapid cryopreservation of biopsied mouse blastocysts and its effect on DNA integrity index

PURPOSE

To evaluate the effect of slow and ultra-rapid freezing on biopsied blastocysts' DNA integrity.

METHODS

Forty eight mouse blastocysts were biopsied of which 16 were cryopreserved by slowly freezing and 17 by vitrification. Fourteen intact blastocysts were slowly cryopreserved and 24 were vitrified. Eighteen fresh intact blastocysts and fifteen biopsied blastocysts served as controls. The DNA integrity index of all blastocysts was evaluated using (TUNEL) staining and confocal imaging

RESULTS

Both slow freezing and vitrification of biopsied blastocysts induced apoptosis to a similar extent. Biopsying blastocysts before vitrification resulted in less apoptosis than vitrification of intact blastocysts.

CONCLUSION

Slow freezing and vitrification are equal options for preservation of biopsied blastocysts as regards the DNA integrity index (DII). Biopsied blastocysts better tolerate vitrification than intact expanded blastocysts.

SNP microarray-based 24 chromosome aneuploidy screening is significantly more consistent than FISH

Many studies estimate that chromosomal mosaicism within the cleavage-stage human embryo is high. However, comparison of two unique methods of aneuploidy screening of blastomeres within the same embryo has not been conducted and may indicate whether mosaicism has been overestimated due to technical inconsistency rather than the biological phenomena. The present study investigates the prevalence of chromosomal abnormality and mosaicism found with two different single cell aneuploidy screening techniques. Thirteen arrested cleavage-stage embryos were studied. Each was biopsied into individual cells (n = 160). The cells from each embryo were randomized into two groups. Those destined for FISH-based aneuploidy screening (n = 75) were fixed, one cell per slide. Cells for SNP microarray-based aneuploidy screening (n = 85) were put into individual tubes. Microarray was significantly more reliable (96%) than FISH (83%) for providing an interpretable result (P = 0.004). Markedly different results were obtained when comparing microarray and FISH results from individual embryos. Mosaicism was significantly less commonly observed by microarray (31%) than by FISH (100%) (P = 0.0005). Although FISH evaluated fewer chromosomes per cell and fewer cells per embryo, FISH still displayed significantly more unique genetic diagnoses per embryo (3.2 ± 0.2) than microarray (1.3 ± 0.2) (P < 0.0001). This is the first prospective, randomized, blinded and paired comparison between microarray and FISH-based aneuploidy screening. SNP microarray-based 24 chromosome aneuploidy screening provides more complete and consistent results than FISH. These results also suggest that FISH technology may overestimate the contribution of mitotic error to the origin of aneuploidy at the cleavage stage of human embryogenesis.

What next for preimplantation genetic screening? A polar body approach!

Screening of human preimplantation embryos for numerical chromosome abnormalities has been conducted mostly at the preimplantation stage using fluorescence in situ hybridization. However, it is clear that preimplantation genetic screening (PGS) as it is currently practiced does not improve live birth rates. Therefore the ESHRE PGS Task Force has decided to start a proof of principle study with the aim of determining whether biopsy of the first and second polar body followed by subsequent analysis of the complete chromosome complement of these polar bodies using an array based technique enables a timely identification of the chromosomal status of an oocyte. If the principle of this approach can be proven, it is obvious that a multicentre randomized controlled trial should then be started to determine the clinical value of this technique. In this way the ESHRE PGS Task Force hopes to redirect preimplantation screening from the blind alley to the main road of assisted reproduction.

Epidemic of plurality and contributions of assisted reproductive technology therein

A commentary on contributions of ART to the pandemic of multiple gestations is presented and mechanistic aspects therein are explored.

[Mastenbroek controversy or how much ink is spilled on preimplantation genetic screening subject]

Preimplantation genetic screening (PGS) of in vitro fertilization (IVF) embryos has been used for advanced maternal age, repeated miscarriages and repeated implantation failure indications. Several non-randomized studies have been published, showing increased implantation rates, decreased miscarriages and trisomy rates. So PGS seemed to improve prognosis for this particular population. In 2004, a prospective randomized study tempered those results, being unable to demonstrate any significant difference of live birth rate with and without PGS in case of advanced maternal age. In July 2007, another multicenter randomized double-blind trial definitely reopened the controversy, reporting that PGS did not increase but instead significantly reduced pregnancy and live birth rates after IVF in women 35 years of age or older. The debate about efficiency and usefulness of PGS is ongoing and other powered randomized studies will be needed to conclude about real PGS usefulness.

Elective single embryo transfer: guidelines for practice British Fertility Society and Association of Clinical Embryologists

Assisted conception treatment is the single most important cause in the increase in multiple pregnancy and births over the last 25 years. Multiple births are associated with significant peri natal morbidity and mortality. Europe has led the way in reducing multiple births by widespread adoption of an elective single embryo policy, which in Belgium is linked to an increase in state funding. Randomized controlled trials suggest that an eSET policy must include the ability to cryopreserve and transfer any remaining quality embryos to obtain parity with a double embryo transfer. This document provides a review of the available evidence with guidelines for practice, to help facilitate the introduction of an eSET policy in the UK.

Preimplantation genetic screening for abnormal number of chromosomes (aneuploidies) in in vitro fertilisation or intracytoplasmic sperm injection

BACKGROUND

In both in vitro fertilisation (IVF) and intracytoplasmic sperm injection (ICSI), selection of the most competent embryo(s) for transfer is generally based on morphological criteria. However, many women fail to achieve a pregnancy after transfer of good quality embryos. One of the presumed causes is that such morphologically normal embryos show an abnormal number of chromosomes (aneuploidies). In preimplantation genetic screening (PGS), embryos are analysed for aneuploidies and only embryos that are euploid for the chromosomes tested are transferred. This technique has been suggested and used to improve pregnancy rates for the following indications: (i) advanced maternal age, (ii) repeated IVF failure, (iii) repeated miscarriage and (iv) testicular sperm extraction (TESE)-ICSI. Although PGS is used more and more often, its effectiveness is still unclear.

OBJECTIVES

To assess the effectiveness of PGS in terms of live births in women undergoing IVF or ICSI treatment.

SEARCH STRATEGY

We searched the Cochrane Menstrual Disorders and Subfertility Group Trials Register, the Cochrane Central Register of Controlled Trials (CENTRAL) (Cochrane Library Issue 1, 2005), MEDLINE (1966 to present) and EMBASE (1980 to present) (searched March 2005) and reference lists of articles. We also contacted authors for providing additional data when necessary.

SELECTION CRITERIA

Trials for all four suggested indications as mentioned above were sought. All relevant published randomised controlled trials were selected. They were eligible for inclusion if the comparison dealt with IVF/ICSI with PGS versus IVF/ICSI without PGS.

DATA COLLECTION AND ANALYSIS

Relevant data were extracted independently by two authors. All trials were screened and analysed according to predetermined quality criteria. Validity was assessed in terms of method of randomisation, completeness of follow-up, intention-to-treat analysis and presence or absence of blinding. The primary outcome measure was live birth rate per woman. Secondary outcome measures were the proportion of women reaching embryo transfer, mean number of embryos transferred per transfer, clinical pregnancy rate, multiple pregnancy rate, miscarriage rate, ongoing pregnancy rate, proportion of women reaching embryo transfer after cryopreservation and proportion of women whose child has a congenital malformation.

MAIN RESULTS

Two randomised controlled trials met our predetermined eligibility criteria. These trials used PGS for advanced maternal age. The primary outcome of live birth rate per woman was not significantly different in the PGS and control groups, though data were only available from one study. The live birth rate was 11% (21 out of 199) in the PGS group, versus 15% (29 out of 190) in the control group (OR 0.65; 95% CI 0.36 to 1.19). For a control group rate of 15%, these data suggest a live birth rate using PGS of between 4% and 17%. Ongoing pregnancy rate was provided in both studies. This was not significantly different with a combined odds ratio of 0.64 (95% CI 0.37 to 1.09). For a control group rate of 20%, this suggests an ongoing pregnancy rate using PGS of between 8% and 21%.

AUTHORS' CONCLUSIONS

To date there is insufficient data to determine whether PGS is an effective intervention in IVF/ICSI for improving live birth rates. Available data on PGS for advanced maternal age showed no difference in live birth rate and ongoing pregnancy rate. However, only two randomised trials were found, of which one included only 39 patients. For both studies comments on their methodological quality can be made. Therefore more properly conducted randomised controlled trials are needed. Until such trials have been performed PGS should not be used in routine patient care.