Preimplantation genetic diagnosis does not increase pregnancy rates in patients at risk for aneuploidy

Reproductive outcomes of single frozen-thawed embryo transfer in patients with endometriosis after preimplantation genetic testing

PURPOSE

The reproductive outcomes of patients with endometriosis who are infertile have attracted recent attention. We aimed to explore whether endometriosis affects endometrial receptivity by observing pregnancy outcomes following a euploid blastocyst frozen embryo transfer.

METHODS

This retrospective cohort study analyzed the data of patients with endometriosis from the reproductive hospital affiliated to Shandong University between January 2015 and December 2021. Control groups were matched using the 1:3 propensity score. The live birth, clinical pregnancy, biochemical pregnancy, clinical abortion, premature birth, and aneuploid rates were compared between the control group and endometriosis group.

RESULTS

A total of 625 patients who underwent preimplantation genetic testing (PGT) prior to embryo implantation were included in the analysis. There were no significant differences in the live birth, clinical pregnancy, biochemical pregnancy, clinical abortion, and premature birth rates between the two groups. The aneuploidy rate of blastocysts obtained from the endometriosis group was higher than that of the control group (P = 0.012).

CONCLUSION

Pregnancy outcomes using frozen embryos after PGT in patients with endometriosis did not differ from those in other women experiencing infertility. However, endometriosis may affect the quality of oocytes, resulting in a higher rate of aneuploidy.

Current Applications and Controversies in Preimplantation Genetic Testing for Aneuploidies (PGT-A) in In Vitro Fertilization

Preimplantation genetic testing for aneuploidy (PGT-A) has evolved over recent years, including improvements in embryo culture, biopsy, transfer, and genetic testing. The application of new comprehensive chromosome screening analysis has improved the accuracy in determining the chromosomal status of the analyzed sample, but it has brought new challenges such as the management of partial aneuploidies and mosaicisms. For the past two decades, PGT-A has been involved in a controversy regarding its efficiency in improving IVF outcomes, despite its widespread worldwide implementation. Understanding the impact of embryo aneuploidy in IVF (in vitro fertilization) should theoretically allow improving reproductive outcomes. This review of the literature aims to describe the impact of aneuploidy in human reproduction and how PGT-A was introduced to overcome this obstacle in IVF (in vitro fertilization). The article will try to analyze and summarize the evolution of the PGT-A in the recent years, and its current applications and limitations, as well as the controversy it generates. Conflicting published data could indicate the lacking value of a single biopsied sample to determine embryo chromosomal status and/or the lack of standardized methods for embryo culture and management and genetic analysis among other factors. It has to be considered that PGT-A may not be a universal test to improve the reproductive potential in IVF patients, rather each clinic should evaluate the efficacy of PGT-A in their IVF program based on their population, skills, and limitations.

Should we transfer poor quality embryos?

Background

To evaluate if it is safe and effective to transfer poor quality embryos.

Methods

It was a retrospective analysis using individual patient data with positive controls. All patients undergoing embryo transfers of poor quality embryos on day 3 or on day 5 as part of fresh In Vitro Fertilization (IVF) cycles performed between 2012 and 2016. This study assessed a total of 738 poor quality embryos from 488 IVF programs. 261 embryo transfers were performed on day 3 (402 embryos were transferred) and 227 on day 5 (336 embryos were transferred). Control group consisted of 9893 fair and good quality embryos from 5994 IVF programs. Outcome rates were compared with two-tailed Fisher exact test using fisher.test function in R software. 95% confidence intervals for proportions were calculated using the Clopper-Pearson method with binom.test function in R. The groups of patients with poor vs. good and fair quality embryos were compared by age, body mass index(BMI), number of oocytes, female and male main diagnosis, cycle type, controlled ovarian stimulation (COS) protocol, the starting day of gonadotropin administration, the starting dose of gonadotropins, the total dose of gonadotropins, the total number of days of gonadotropins administration, the starting day of gonadotropin-releasing hormone (GnRH) agonist administration, the total number of ampoules of GnRH-agonist used, day of the trigger of ovulation administration and the type of the trigger of ovulation using the Student’s t-test for interval variables and with the chi-square test for nominal variables.

Results

No significant differences in the implantation rate, clinical pregnancy rate, miscarriage rate, live births, and the number of children born were found between the groups of poor quality embryos transferred on day 3 and day 5. Though the implantation rate was lower for the group of poor quality embryos, than for the control (13.9% vs 37.2%), statistically significant differences between the proportion of implanted embryos which resulted in clinical pregnancies and live births in both groups were not observed (72% vs 78.2 and 55.8% vs 62.0% respectively).

Conclusion

Transfer of poor quality embryos at either day 3 or day 5 have a low potential for implantation, though those embryos which successfully implanted have the same potential for live birth as the embryos of fair and good quality. This study supports that it is safe to transfer poor quality embryos when they are the only option for fresh embryo transfer (ET).

Preimplantation genetic diagnosis for monogenic diseases: overview and emerging issues

Preimplantation genetic diagnosis (PGD) is an established reproductive option for couples at risk of conceiving a pregnancy affected with a known genetic disease, who wish to avoid an (additional) affected child, termination of pregnancy or recurrent miscarriages. Early technologies concentrated on different approaches to direct mutation testing for monogenic diseases using single cell PCR protocols, or sex selection by fluorescent in situ hybridization for X-linked monogenic disease. Development of multiplex fluorescent PCR allowed simultaneously testing of linked markers alongside the mutation test, increasing the accuracy by controlling for contamination and identifying allele drop-out. The advent of highly effective whole genome amplification methods has opened the way for new technologies such as preimplantation genetic haplotyping and microarrays, thus increasing the number of genetic defects that can be detected in preimplantation embryos; the number of cases carried out and the new indications tested increases each year. Different countries have taken very different approaches to legislating and regulating PGD, giving rise to the phenomenon of reproductive tourism. PGD is now being performed for scenarios previously not undertaken using prenatal diagnosis, some of which raise significant ethical concerns. While PGD has benefited many couples aiming to have healthy children, ethical concerns remain over inappropriate use of this technology.

Time-Lapse Cleavage Rating Predicts Human Embryo Viability

Chronology of three consecutive mitotic events in human pre-implantation embryos was examined by time-lapse imaging. In zygotes producing well-formed and pregnancy-yielding expanded blastocysts, uniform time-patterning of cleavage clusters (c) and interphases (i) was revealed: i2=11±1, i3=15±1, i4=23±1 h / c2=15±5, c3=40±10, c4=55±15 min. Oppositely, shortened or prolonged durations of one or more cell cycles were strongly predictive of poor implantation and development. Furthermore, trichotomic mitosis was discovered in 17 % of cases - zygotes cleaved into 3 blastomeres and 2-cell embryos into 5-6 cells (instead of normal 2 and 4). During conventional clinical assessment, such embryos are indistinguishable from normal, often considered just-in-course of the next cell cycle. Only detailed time-lapse monitoring paced at 10-minute intervals had proven all these embryos to be absolutely unviable, even in rare cases when they reduced their hypercellularity to normal cell counts via cell-cell fusion. Overall, we demonstrate that time-lapse embryo cleavage rating (ECR) as a standalone diagnostic procedure allows for effective identification of viable early embryos with 90 % specificity, while elimination of good-looking but unviable embryos can be assumed with a specificity of 100 %. Thus, making this non-invasive and contactless approach worth of addition to routine embryo screening in clinical IVF programs.

A comparison of ejaculated and testicular spermatozoa aneuploidy rates in patients with high sperm DNA damage

Testicular spermatozoa are utilized to achieve pregnancy in couples with severe male factor infertility. Several studies suggest that aneuploidy rates in spermatozoa are elevated at the testicular level in infertile patients compared to ejaculates of normal controls. However, essential data regarding aneuploidy rates between ejaculated and testicular spermatozoa in the same individuals is lacking. The purpose of our study was to compare aneuploidy rates at the testicular and post-testicular level from the same patients with persistently high sperm DNA damage. Ejaculates and testicular biopsies were obtained from eight patients with persistently high DNA damage (>30%). Both ejaculated and testicular samples were analyzed for sperm DNA damage and sperm aneuploidy for chromosomes 13, 18, 21, X, and Y. In addition, semen samples from ten normozoospermic men presenting for fertility evaluation served as a control group. A strong correlation between the alteration of spermatogenesis and chromatin deterioration was observed in our study. In the same individuals, testicular samples showed a significantly lower DNA damage compared to ejaculated spermatozoa (14.9% ± 5.0 vs. 40.6% ± 14.8, P<0.05), but significantly higher aneuploidy rates for the five analyzed chromosomes (12.41% ± 3.7 vs. 5.77% ± 1.2, P<0.05). While testicular spermatozoa appear favourable for ICSI in terms of lower DNA damage, this potential advantage could be offset by the higher aneuploidy rates in testicular spermatozoa.

Preimplantation diagnosis of genetic diseases

One of the landmarks in clinical genetics is prenatal diagnosis of genetic disorders. The recent advances in the field have made it possible to diagnose the genetic conditions in the embryos before implantation in a setting of in vitro fertilization. Polymerase chain reaction and fluorescence in situ hybridization are the two common techniques employed on a single or two cells obtained via embryo biopsy. The couple who seek in vitro fertilization may screen their embryos for aneuploidy and the couple at risk for a monogenic disorder but averse to abortion of the affected fetuses after prenatal diagnosis, are likely to be the best candidates to undergo this procedure. This article reviews the technique, indications, benefits, and limitations of pre-implantation genetic testing in clinical practice.

Quantitative decision-making in preimplantation genetic (aneuploidy) screening (PGS)

PURPOSE

To analyze using hypergeometric probability statistics the impact of performing preimplantation genetic screening (PGS) on a cohort of day 3 cleavage stage embryos.

METHODS

Statistical mathematical modeling.

RESULTS

We find the benefit of performing PGS is highly dependent on the number of day 3 embryos available for biopsy. Additional hidden variables that determine the outcome of PGS are the rates of aneuploidy and mosaicism, and the probability of a chromosomally mosaic embryo to test "normal". If PGS is performed, our analysis shows that many combinations of the number of biopsiable embryos, and the rates of aneuploidy and mosaicism results in a marginal benefit from the intervention. Other combinations are detrimental if PGS is actually undertaken. Finally, increases in PGS error rates lead to a rapid loss in the ability of PGS to provide useful discriminatory information.

CONCLUSION

We set out the statistical framework to determine the limits of PGS when a specific number of day 3 preimplantation embryos are available for biopsy. In general, PGS cannot be recommended a priori for a specific clinical situation due to the statistical uncertainties associated with the different hidden variable quantitative parameters considered important to the clinical outcome.

IVF/ICSI with or without preimplantation genetic screening for aneuploidy in couples without genetic disorders: a systematic review and meta-analysis

PURPOSE

To assess the efficacy of preimplantation genetic screening to increase ongoing pregnancy rates in couples without known genetic disorders.

METHODS

Systematic review and meta-analysis of randomized controlled trials. Two reviewers independently determined study eligibility and extracted data.

RESULTS

Ten randomized trials (1,512 women) were included. The quality of evidence was moderate. Meta-analyses using a random-effects model suggest that PGS has a lower rate of ongoing pregnancies (risk ratio=0.73, 95% confidence interval 0.62-0.87) and a lower rate of live births (risk ratio=0.76, 95% confidence interval 0.64-0.91) than standard in vitro fertilization/intracytoplasmic sperm injection.

CONCLUSIONS

In women with poor prognosis or in general in vitro fertilization program, in vitro fertilization/intracytoplasmic sperm injection with preimplantation genetic screening for aneuploidy does not increase but instead was associated with lower rates of ongoing pregnancies and live births. The use of preimplantation genetic screening in daily practice does not appear to be justified.

Preimplantation genetic screening for aneuploidy of embryos after in vitro fertilization in women aged at least 35 years: a prospective randomized trial

OBJECTIVE

To test the hypothesis that patients with advanced maternal age (AMA) have a higher implantation rate (IR) after embryo transfer of embryos with a normal chromosomal pattern for the chromosomes studied with preimplantation genetic screening (PGS) compared with patients who had an embryo transfer without PGS.

DESIGN

Prospective randomized controlled trial (RCT).

SETTING

Academic tertiary setting.

PATIENT(S)

Patients with AMA (> or =35 years).

INTERVENTION(S)

In an RCT, the clinical IR per embryo transferred was compared after embryo transfer on day 5 or 6 between the PGS group (analysis of chromosomes 13, 16, 18, 21, 22, X, and Y) and the Control group without PGS.

MAIN OUTCOME MEASURE(S)

No differences were observed between the PGS group and the Control group for the clinical IR (15.1%; 14.9%; rate ratio 1.01; exact confidence interval [CI], 0.25-5.27), the ongoing IR (at 12 weeks) (9.4%; 14.9%), and the live born rate per embryo transferred (9.4%; 14.9%; rate ratio 0.63; exact CI, 0.08-3.37). Fewer embryos were transferred in the PGS group (1.6 +/- 0.6) than in the Control group (2.0 +/- 0.6). A normal diploid status was observed in 30.3% of the embryos screened by PGS.

CONCLUSION(S)

In this RCT, the results did not confirm the hypothesis that PGS results in improved reproductive outcome in patients with AMA.

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.

Preimplantation genetic diagnosis: an overview of socio-ethical and legal considerations

Preimplantation genetic diagnosis (PGD) permits the selection of embryos of a particular genotype prior to implantation. As a reproductive technology involving embryo selection, PGD has become associated with considerable controversy. This review examines some of the ethical, legal, and social issues raised by PGD. Relevant ethical considerations include the status of the embryo and the interests and duties of the parents. On a social policy level, considerations of access as well as the impact of this technology on families, women, and physician's duties also warrant consideration. An analysis of these issues in the context of using PGD for selecting embryos unaffected by a serious disorder and for sex selection is presented. We also present a brief survey of PGD-related regulatory schemes in several countries, including the United Kingdom and the United States.

Preimplantation genetic screening: "established" and ready for prime time?

Unless attempts to improve pregnancy rates and/or diminish miscarriage rates through preimplantation genetic screening (PGS) are applied to only carefully selected patients, they will fail. Because specific PGS indications have remained undefined, PGS should be considered an experimental procedure.

Researching human oocyte cryopreservation: ethical issues

OBJECTIVE

To evaluate some ethical concerns related to the selection of participants for oocyte cryopreservation research.

DESIGN

Review of ethical issues related to human oocyte cryopreservation research.

SETTING

Academic medical center.

PATIENT(S)

None.

INTERVENTION(S)

None.

MAIN OUTCOME MEASURE(S)

A discussion of some ethical concerns surrounding selection of participants for oocyte cryopreservation research.

RESULT(S)

Human oocyte cryopreservation has the potential to expand reproductive options for infertile couples. Care needs to be taken, however, to carefully select participants in ways that maximizes benefits to them and to society and minimizes risks. Infertility programs can do so by trying to recruit women who stand to benefit the most from participating in oocyte cryopreservation protocols.

CONCLUSION(S)

Biomedical research is necessary to improve current medical therapies. Oocyte cryopreservation can increase the flexibility of assisted reproductive programs and offer hope to a significant number of infertile couples. Nonetheless, scientific research cannot be attentive only to the creation of new knowledge and new technologies; it also is inextricably tied to ethical considerations about the well-being of participants.

Elucidating the origin of chromosomal aberrations in IVF embryos by preimplantation genetic analysis

Preimplantation genetic screening (PGS) has been proposed as a method for improving success rates in patients with repeated IVF failures. This approach is based on the hypothesis that such failures are the result of aneuploid embryos. It has been suggested that FISH analysis of blastomeres removed from preimplantation embryos represent the chromosomal constitution of the entire embryo. However, it is not yet clear whether it also represents the chromosomal constitution of the implanted embryo. PGS reanalysis on day 5 of embryos designated as "aneuploid" on day 3 may demonstrate a high rate of mosaicism for chromosomal aberration. Some of these mosaic embryos are capable of developing into normal embryos by "self-correction". Others, however, may accumulate additional chromosomal anomalies. It is therefore concluded that the chromosomal constitution of a preimplantation embryo may evolve during early cleavages. Meiotic and post zygotic mitotic errors may account for these chromosomal aberrations. This review will focus on elucidating the origin of chromosomal changes during preimplantation embryo development by studying their chromosomal constitution at different stages.

Preimplantation genetic screening in older women: a cost-effectiveness analysis

OBJECTIVE

To compare the strategy of traditional IVF with prenatal diagnosis versus IVF with preimplantation genetic screening (IVF/PGS) to prevent aneuploid births in women with advanced maternal age.

DESIGN

A decision tree analytic model was created to compare IVF alone versus IVF/PGS to evaluate which strategy is the least costly per healthy (euploid) infant.

SETTING

Outpatient IVF practices.

PATIENT(S)

Infertile women, 38-40 and >40 years old.

INTERVENTION(S)

IVF or IVF/PGS.

MAIN OUTCOME MEASURE(S)

Cost per healthy infant.

RESULT(S)

Using base-case estimates of costs and probabilities in women aged 38-40 years, after a maximum of two fresh IVF cycles and two frozen cycles, the chance of having a healthy infant was 37.8% with IVF alone versus 21.7% with IVF/PGS. The average cost for each strategy is $25,700, but the cost per healthy infant is substantially higher when IVF/PGS is applied as opposed to IVF alone ($118,713 vs. $68,026). To assess the robustness of the model, all probabilities were varied simultaneously in a Monte Carlo simulation, and in 96.2% of trials, IVF alone proved to be the most cost-effective option. Conversely, our data demonstrate that in women aged >40, IVF and IVF/PGS are essentially equal in terms of cost-effectiveness ($122,000 vs. $118,713).

CONCLUSION(S)

IVF alone is less costly per healthy infant than IVF/PGS in women ages 38-40.

Patient willingness to participate in a clinical trial with preimplantation genetic diagnosis

OBJECTIVE

To investigate patients' interest in preimplantation genetic diagnosis (PGD) as a method for aneuploidy screening and their willingness to participate in a clinical trial using PGD.

DESIGN

Anonymous questionnaire.

SETTING

University infertility clinic.

PATIENT(S)

Women seeking treatment for infertility at the study clinic.

INTERVENTION(S)

Subjects completed a two-part structured questionnaire. The questionnaire included demographic and fertility history questions, followed by opinion questions on testing for genetic diseases. The second portion of the questionnaire included opinion questions about willingness to use PGD and to participate in a clinical trial using PGD after reading a document explaining PGD.

MAIN OUTCOME MEASURE(S)

Patients' interest in using PGD and willingness to participate in a clinical trial involving PGD.

RESULT(S)

Before reading a description of PGD, 84% of participants indicated that they were interested in having their embryos tested. The majority (86%) remained interested in testing their embryos with PGD after reading the informational paragraph. Most (91%) of the women who remained interested in PGD also indicated a willingness to participate in a clinical trial involving PGD. Of the patients who initially were not interested in testing their embryos, nearly half of them (47%) indicated an interest in PGD after reading the informational paragraph, and nearly all of those who changed their mind were willing to be in a trial.

CONCLUSION(S)

Many women undergoing IVF are interested in the possibility of utilizing PGD for aneuploidy screening. Better evidence is needed regarding outcomes using PGD for this indication before it can be routinely incorporated into practice. A clinical trial using PGD in this setting appears possible because a majority of the patients, in this survey, would be willing to participate.

Assisted reproductive technology practice patterns and the impact of embryo transfer guidelines in the United States

OBJECTIVE

[1] To evaluate trends in number of embryos transferred and resultant high-order multiple (HOM) pregnancy rates by Society for Assisted Reproductive Technology (SART)-member clinics between 1996 and 2003 and [2] to relate these practice patterns and outcomes to clinic compliance with SART-American Society for Reproductive Medicine (ASRM) embryo transfer guidelines.

DESIGN

Retrospective.

SETTING

Society for Assisted Reproductive Technology-member fertility centers in the United States.

PATIENT(S)

Five hundred thirty-six thousand, five hundred twenty-four fresh, nondonor IVF cycles.

INTERVENTION(S)

None.

MAIN OUTCOME MEASURE(S)

Number of embryos transferred; pregnancy rates; implantation rates; and proportion of singleton, twin, and HOM pregnancies.

RESULT(S)

The number of embryos transferred declined each year. High-order multiple pregnancy rates also declined, whereas the twin rates remained stable. The most pronounced declines in number transferred occurred immediately after publication of SART-ASRM embryo transfer guidelines. After stratifying clinics according to mean and modal number of embryos transferred, clinics transferring the fewest embryos in women <35 years of age had the highest mean implantation and pregnancy rates. Furthermore, the percentage of clinics transferring two embryos to a majority of women <35 years of age increased from 3.3% in 1996 to 49.9% in 2003.

CONCLUSION(S)

The implementation of SART-ASRM embryo transfer guidelines is associated with significant reductions in the number of embryos being transferred, along with reductions of HOM pregnancies. Initiatives to further reduce twin pregnancies and encourage singleton gestation outcomes are outlined.

Increased efficiency of preimplantation genetic diagnosis for infertility using "no result rescue"

OBJECTIVE

To improve preimplantation genetic diagnosis (PGD) accuracy by using "no result rescue" (NRR) consisting of the reanalysis of dubious results with additional probes binding to a locus different from the one previously analyzed.

DESIGN

Prospective study of PGD cycles with and without reanalysis of inconclusive results.

SETTING

PGD laboratory.

PATIENT(S)

Patients undergoing PGD for infertility or Robertsonian translocations.

INTERVENTION(S)

Nuclei from day 3 biopsied embryos were analyzed with fluorescence in situ hybridization for chromosomes X,Y, 13, 15, 16, 17, 18, 21, and 22. When inconclusive results were obtained, NRR was performed. In addition, 100 PGD cycles using NRR were matched to controls according to maternal age, previous failed cycles, number of zygotes, number of eggs, and date of retrieval.

MAIN OUTCOME MEASURE(S)

Determination of frequency of inconclusive results and error rate after use of additional probes. Comparison of frequency of inconclusive results with prior PGD results when NRR was not used. Assisted reproductive technology outcome was compared between PGD using NRR and controls not using PGD.

RESULT(S)

After analysis of 34,831 blastomeres from 34,225 embryos, 2,609 blastomeres (7.5%) showed inconclusive results. After NRR on those 2,609 blastomeres, the number of cells with inconclusive results was reduced to 3.1% (P<.001). After the introduction of NRR, fluorescence in situ hybridization errors, measured as discrepancies between the PGD diagnosis and the analysis of the nonreplaced embryo, decreased from 13.6% to 4.7% (P<.001). PGD with NRR significantly improved implantation rates, from 20% to 31%, and reduced spontaneous abortions from 27% to 6%.

CONCLUSION(S)

The use of NRR has been proven to be a powerful tool to reduce the error rate and the frequency of inconclusive results in PGD, both parameters of high importance to assess quality of PGD laboratories. Indeed, these parameters are two of the few measurable criteria to measure PGD laboratories. In a parallel controlled study, PGD with NRR significantly improved implantation rates and reduced spontaneous abortions, showing that PGD is more efficient in selecting embryos that will reach term.

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.

Removal of 2 cells from cleavage stage embryos is likely to reduce the efficacy of chromosomal tests that are used to enhance implantation rates

OBJECTIVE

To evaluate whether differences in results between studies that involve preimplantation genetic diagnosis for chromosome testing are affected by technology, such as the number of cells to be biopsied or by differences in study design.

DESIGN

Evaluation of studies of aneuploidy testing according to the use of probes, fixation technology, error determination, and number of cells per embryo analyzed.

SETTING

Preimplantation genetic diagnosis laboratories.

PATIENT(S)

Patients in published studies who underwent preimplantation genetic diagnosis for infertility or repeated pregnancy loss.

INTERVENTION(S)

As determined by each evaluated study, the number of biopsied cells and its effect on further development was evaluated by a comparison of models of embryo freezing and partial cell loss.

MAIN OUTCOME MEASURE(S)

Use of probes, fixation strategy, number of biopsied cells, and error rate determination of different published studies.

RESULT(S)

Differences in results between studies can be explained by the technology used and are not affected necessarily by differences in design and patient allocation.

CONCLUSION(S)

Studies that contradict the finding that aneuploidy screening improves implantation and lowers miscarriage rates all have > or =1 of the following aspects in common: (I) an excess of cells having been removed; (II) inadequate choice of probes; and (III) suboptimal fixation technology.

Current value of preimplantation genetic aneuploidy screening in IVF

Preimplantation genetic aneuploidy screening (PGS) has been performed during the last decade as a way of enhancing embryo selection in patients with an increased incidence of embryonic numerical chromosome abnormalities (advanced maternal age, recurrent miscarriage and recurrent implantation failure). It has been proposed that the replacement of euploid embryos in these patients would result in a higher implantation and pregnancy rate and a reduced miscarriage rate. Additionally, the transfer of fewer embryos could reduce the chances for multiple pregnancies in all IVF patients. Although, to date, multiple studies have addressed this issue, contradictory results have been encountered. As a result, the effectiveness of aneuploidy screening remains to be established. Moreover, child outcome studies documenting the safety of this procedure are needed. The aim of this review is to summarize the available evidence concerning the use of PGS to determine the current value of the technique.

Advanced maternal age as an indication for preimplantation genetic diagnosis (PGD)--the need for more judicious application in clinically assisted reproduction

BACKGROUND

Pre-implantation genetic diagnosis (PGD) is often recommended for routine screening of chromosomal aneuploidy in older women undergoing clinical assisted reproduction, even though its prognostic value on this group of patients is rather ambiguous. What is needed is a clear set of ethical guidelines in the marketing of this technically complex and expensive procedure to patients who are neither suffers nor carriers of serious genetic diseases.

METHODS

Professional counseling would be required to enable an informed decision from the patient. Differences in the prognostic value of PGD for different medical indications must be clearly presented to the patient and they must also be told that PGD is not a completely 'fool-proof' means of preventing birth defects. What may be detected are some genetic syndromes and conditions associated with cytogenetic abnormalities.

RESULTS

The patient must be made aware that the results of previous studies have demonstrated that the overwhelming majority of chromosomally abnormal oocytes and embryos either fail to fertilize or implant, and therefore have a relatively low chance of resulting in a live birth with chromosomal defects. Statistical data, particularly the concept of relative risk must clearly be presented to the patient without exaggerating the risk of birth defects. The patient must also be rightfully informed that PGD carries a small risk of damaging the embryo, which could compromise chances of conception.

CONCLUSIONS

PGD should be judiciously indicated for advanced maternal age in clinically assisted reproduction. Other diagnostic options that may be cheaper, and which also possess a high level of accuracy should be presented first to the patient i.e. amniocentesis, chorionic villus biopsy and ultrasonargraphy.