Degree of mosaicism in trophectoderm does not predict pregnancy potential: a corrected analysis of pregnancy outcomes following transfer of mosaic embryos

A review of the 2021/2022 PGDIS Position Statement on the transfer of mosaic embryos

The practice of preimplantation genetic testing for aneuploidy (PGT-A) in association with in vitro fertilization (IVF) since 2016 has been mostly directed by three highly controversial guidance documents issued by the Preimplantation Genetic Diagnosis International Society (PGDIS). Because these documents are so influential on worldwide IVF practice, the most recent one is here the subject of a detailed review, again revealing important misrepresentations and internal contradictions. Most importantly, however, this most recent guidance document still does not prevent the non-use and/or disposal of large numbers of embryos with substantial pregnancy and live-birth potential and, therefore, continues to propagate an IVF practice harmful to many infertile women.

What proportion of embryos should be considered for transfer following a mosaic diagnosis? A study of 115 clinics from a central diagnostic laboratory

PURPOSE

The aim of this study is to identify what proportion of mosaic embryo diagnoses should be considered for transfer, and thereby assess the impact on patient cases.

METHODS

We categorised mosaic embryos into 3 groups; high, medium and low priority for transfer based on the percentage of biopsy sample being aneuploid and the chromosomes involved. The categories were applied to those patients that had no euploid embryo diagnoses but 1 or more mosaic embryos identified as mosaic available after PGT-A.

RESULTS

In total, 6614 PGT-A cases from 115 clinics and a single diagnostic laboratory were reviewed. Further, 1384 [20.9%] cases only had aneuploid embryos, 4538 [68.6%] cases had one or more euploid embryos and 692 [10.5%] cases had no euploid and one or more mosaic embryo. The mosaic embryos in the no euploid, one or more mosaic group, when reviewed using priorities, resulted in: 111 [1.7%] of cases having at least one high priority mosaic available. 184 [2.8%] of cases having no high priority but at least one medium priority mosaic available. 397 [6.0%] of cases only having low priority mosaic embryos available.

CONCLUSION

Based on this data, embryos identified as mosaic will only be considered for transfer in the first instance for around 4.5% (when taking high and medium priority and excluding low priority cases) of all PGT-A cases.

Preimplantation genetic testing for aneuploidy: The management of mosaic embryos

As the resolution and accuracy of diagnostic techniques for preimplantation genetic testing for aneuploidy (PGT-A) are improving, more mosaic embryos are being identified. Several studies have provided evidence that mosaic embryos have reproductive potential for implantation and healthy live birth. Notably, mosaic embryos with less than 50% aneuploidy have yielded a live birth rate similar to euploid embryos. This concept has led to a major shift in current PGT-A practice, but further evidence and theoretically relevant data are required. Proper guidelines for selecting mosaic embryos suitable for transfer will reduce the number of discarded embryos and increase the chances of successful embryo transfer. We present an updated review of clinical outcomes and practice recommendations for the transfer of mosaic embryos using PGT-A.

Factors affecting clinical manifestation of chromosomal imbalance in carriers of segmental autosomal mosaicism: differential impact of gender

Mosaicism for unbalanced chromosomal rearrangements segmental mosaicism (SM) is rare, both in patients referred for cytogenetic testing and in prenatal diagnoses. In contrast, in preimplantation embryos SM is a frequent finding and, therefore, is even more challenging. However, there is no consistency among results of published studies on the clinical outcomes of embryos with SM, primarily due to the small number of reported cases. Moreover, there is the problem of predicting the potential for the optimal development of a mosaic embryo to a healthy individual. Therefore, we suggested comparing factors predisposing to favorable and poor prognoses, identified in postnatal and prenatal cohorts of SM carriers, with those obtained from studies on preimplantation embryos. We analyzed 580 published cases of SM including (i) postnatally diagnosed affected carriers, (ii) clinically asymptomatic carriers, (iii) prenatally diagnosed carriers, and (iv) miscarriages. We observed a concordance with preimplantation diagnoses regarding the clinical significance of the extent of mosaicism as well as a predominance of deletions over other types of rearrangements. However, there is no concordance regarding excessive involvement of chromosomes 1, 5, and 9 in unbalanced rearrangements and a preferential involvement of larger chromosomes compared to short ones. Paternal age was not found to be associated with SM in postnatally disease-defined individuals. We have identified maternal age and preferential involvement of chromosome 18 in rearrangements associated with clinical manifestations. Male predominance was found among normal pregnancy outcomes and among disease-defined carriers of rearrangements resulting in a gain of genomic material. Female predominance was found among abnormal pregnancy outcomes, among disease-defined carriers of loss and gain/loss rearrangements, and among transmitting carriers of gonadal SM, both affected and asymptomatic. According to data obtained from “post-embryo” studies, clinical manifestations of chromosomal imbalance are associated with a high proportion of abnormal cells, female gender, the type of rearrangement and involved chromosome(s), and maternal age. We believe these data are instructive in the challenging medical genetic counseling of parents faced with no option other than transfer of an embryo with segmental mosaicism.

Are tri-pronuclear embryos that show two normal-sized pronuclei and additional smaller pronuclei useful for embryo transfer?

Purpose

This study aimed to analyze whether tripronuclear (3PN) zygotes, with two normal‐sized PNs and an additional smaller PN (2.1PN), can be used for embryo transfer.

Method(s)

A retrospective embryo cohort study was conducted on 695 patients who underwent intracytoplasmic sperm injection treatment. Blastocyst formation rates were compared between 2.1PN and 2PN zygotes and PGT‐A analysis was performed on 15 blastocysts derived from 2.1PN zygotes.

Result(s)

Blastocyst formation rates were comparable between 2.1PN (43.8%) and 2PN zygotes (54.8%; p = 0.212). The rates of blastocysts with good morphology derived from 2.1 PN and 2PN zygotes were 18.8% and 25.5%, respectively. No significant differences were detected (p = 0.383). All of the analyzed blastocysts were diploid; however, 13 of these were found to be aneuploid, with a further two being mosaic.

Conclusion

Our results suggest that 2.1PN embryos can reach blastocyst stage. These blastocysts were diploid, however, predominantly aneuploid, and therefore could not be used for embryo transfer.

Evidence-based clinical prioritization of embryos with mosaic results: a systematic review and meta-analysis

PURPOSE

The purpose of this review and meta-analysis is to standardize the practice of mosaic embryo transfer, based on the current available evidence.

METHODS

This is a systematic review and meta-analysis. Relevant studies published were comprehensively selected using PubMed, Medline, Embase, and CENTRAL until 5 March 2021. Prospective and retrospective studies reporting the genetic analysis and clinical outcomes of mosaic embryo transfer were included. Risk of bias assessment was based on the Newcastle-Ottawa scale for the non-randomized studies. The primary and secondary outcomes were combined ongoing pregnancy and live birth rate and miscarriage rate, respectively.

RESULTS

There were no differences between low and high mosaic embryos when a cut-off of 40% was used in terms of OP/LBR and SAB. However, low mosaics with a cut-off of 50% compared to high mosaics showed a significantly higher OP/LBR in the NGS but not in the a-CGH group, and a significantly lower risk of SAB. No differences were noted between mosaic monosomies versus trisomies and single versus double mosaics for both OP/LBR and SAB. Finally, segmental mosaics showed a higher OP/LBR and a lower SAB compared to whole chromosomes, and single and double mosaics had a higher OP/LBR compared to complex mosaics.

CONCLUSIONS

A cut-off of 50% in defining low versus high mosaic embryos is preferable to a threshold of 40% when using NGS platform. No priority was established for mosaic trisomies over monosomies. Single and double mosaics must be preferred over complex mosaics and segmental mosaics must be preferred over whole chromosome mosaics. These results should be interpreted in the context of specific chromosomes involved in the mosaicism.

The "mosaic" embryo: misconceptions and misinterpretations in preimplantation genetic testing for aneuploidy

Preimplantation genetic testing for aneuploidy (PGT-A) remains one of the most controversial topics in reproductive medicine. With more than 40% of in vitro fertilization cycles in the United States reportedly involving PGT, both those in favor of and those opposed to PGT-A have significant interest in the efficacy of PGT-A. Ongoing issues include what patient population, if any, benefits from PGT-A, the true frequency of chromosomal mosaicism, whether embryonic aneuploidies self-correct, and how practitioners manage embryos designated as "mosaic." This review addresses several misconceptions and misinterpretations of data surrounding the genetic analysis and prediction of mosaicism in the preimplantation embryo.

Proteomics based drug repositioning applied to improve in vitro fertilization implantation: an artificial intelligence model

Embryo implantation is one of the most inefficient steps in assisted reproduction, so the identifying drugs with a potential clinical application to improve it has a strong interest. This work applies artificial intelligence and systems biology-based mathematical modeling strategies to unveil potential treatments by computationally analyzing and integrating available molecular and clinical data from patients. The mathematical models of embryo implantation computationally generated here simulate the molecular networks underneath this biological process. Once generated, these models were analyzed in order to identify potential repositioned drugs (drugs already used for other indications) able to improve embryo implantation by modulating the molecular pathways involved. Interestingly, the repositioning analysis has identified drugs considering two endpoints: (1) drugs able to modulate the activity of proteins whose role in embryo implantation is already bibliographically acknowledged, and (2) drugs that modulate key proteins in embryo implantation previously predicted through a mechanistic analysis of the mathematical models. This second approach increases the scope open for examination and potential novelty of the repositioning strategy. As a result, a list of 23 drug candidates to improve embryo implantation after IVF was identified by the mathematical models. This list includes many of the compounds already tested for this purpose, which reinforces the predictive capacity of our approach, together with novel repositioned candidates (e.g., Infliximab, Polaprezinc, and Amrinone). In conclusion, the present study exploits existing molecular and clinical information to offer new hypotheses regarding molecular mechanisms in embryo implantation and therapeutic candidates to improve it. This information will be very useful to guide future research.Abbreviations: IVF: in vitro fertilization; EI: Embryo implantation; TPMS: Therapeutic Performance Mapping System; MM: mathematical models; ANN: Artificial Neuronal Networks; TNFα: tumour necrosis factor factor-alpha; HSPs: heat shock proteins; VEGF: vascular endothelial growth factor; PPARA: peroxisome proliferator activated receptor-α PXR: pregnane X receptor; TTR: transthyretin; BED: Biological Effectors Database; MLP: multilayer perceptron.

Biological and Clinical Significance of Mosaicism in Human Preimplantation Embryos

Applications and indications of assisted reproduction technology are expanding, but every new approach is under scrutiny and thorough consideration. Recently, groups of assisted reproduction experts have presented data that support the clinical use of mosaic preimplantation embryos at the blastocyst stage, previously excluded from transfer. In the light of published contemporary studies, with or without clinical outcomes, there is growing evidence that mosaic embryos have the capacity for further in utero development and live birth. Our in-depth discussion will enable readers to better comprehend current developments. This expansion into the spectrum of ART practices requires further evidence and further theoretical documentation, basic research, and ethical support. Therefore, if strict criteria for selecting competent mosaic preimplantation embryos for further transfer, implantation, fetal growth, and healthy birth are applied, fewer embryos will be excluded, and more live births will be achieved. Our review aims to discuss the recent literature on the transfer of mosaic preimplantation embryos. It also highlights controversies as far as the clinical utilization of preimplantation embryos concerns. Finally, it provides the appropriate background to elucidate and highlight cellular and genetic aspects of this novel direction.

Perceptions, motivations and decision regret surrounding preimplantation genetic testing for aneuploidy

STUDY QUESTION

Is there a difference in level of decision regret following IVF treatment between those who choose to complete or not complete preimplantation genetic testing for aneuploidy [PGT-A]?

SUMMARY ANSWER

Approximately one-third of the participants expressed moderate to severe regret (MSR) following their decision to either complete or not complete PGT-A; notably, decision regret was higher in those who chose not to complete PGT-A, primarily driven by significantly higher regret scores in those that experienced a miscarriage after not testing.

WHAT IS KNOWN ALREADY

Previous research has found that 39% of participants who completed PGT-A expressed some degree of decision regret and that negative clinical outcomes, such as lack of euploid embryos, negative pregnancy test or miscarriage, were associated with a higher level of decision regret. To date, there are no published studies assessing the possible disparity in decision regret surrounding PGT-A in a population of IVF patients that either chose to pursue PGT-A or not.

STUDY DESIGN, SIZE, DURATION

An anonymous online survey was distributed to 1583 patients who underwent IVF with or without PGT-A at a single university institution between January 2016 and December 2017. In total, 335 women accessed the survey, 220 met eligibility criteria and 130 completed the full study survey. Six participants were excluded due to refusal of medical record review, and nine participants were excluded after record review due to not meeting eligibility based on cycle start date or completing only embryo banking without attempting transfer. One hundred and fifteen participants were included in the final analysis.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Of the 115 participants included, 55 (48%) completed PGT-A and 60 (52%) did not complete PGT-A. The online survey included four sections: Demographics; Perceptions about PGT-A risks and benefits [scale from 0 (absolutely not true) to 100 (absolutely true)]; Decision-making factors [scale from 0 (not important) to 100 (very important)]; and Brehaut Decision Regret Scale [DRS] [range 0-100, with >25 indicating MSR]. A retrospective chart review was conducted to confirm study eligibility and collect cumulative clinical outcomes of consenting participants who completed the survey.

MAIN RESULTS AND THE ROLE OF CHANCE

Demographics of the PGT-A and no PGT-A cohorts were similar, with the majority of respondents being Caucasian or Asian, unaffiliated with any religion and with a graduate or professional degree. The two groups differed significantly in mean age, with the PGT-A group being slightly older (mean ± SD: 37 ± 3.7 versus 36 ± 3.4; P = 0.048), and in rate of miscarriages, with fewer participants in the PGT-A cohort experiencing a miscarriage (5% versus 22%; P = 0.012). The majority of participants in both PGT-A and no PGT-A cohorts strongly believed in the purported benefits of PGT-A, including that it decreases the risk of birth defects (median 82 versus 77; P = 0.046), improves the chances of having a healthy baby (median 89 versus 74; P = 0.002) and selects the best embryo for transfer (median 85 versus 80; P = 0.049). When asked to report their motivating factors for decision-making, both groups cited physician counseling as important (median 70 versus 71; P = 0.671); however, the PGT-A cohort was more strongly motivated by a desire to not transfer abnormal embryos (median 84 versus 53; P = 0.0001). Comparison of DRS score between those who did or did not undergo PGT-A showed significantly higher median DRS score after not completing PGT-A (median 15 versus 0; P = 0.013). There was a significantly higher proportion of participants who did not complete PGT-A that expressed mild (36% versus 16%) and MSR (32% versus 24%) compared to those who completed PGT-A (χ2 = 9.03, df = 2; P = 0.011). Sub-group analyses of DRS scores by outcomes of clinical pregnancy, miscarriage and live birth revealed that the higher DRS score in those not completing PGT-A was driven by a large increase in regret noted by those with history of a miscarriage (median 45 versus 0; P = 0.018). Multivariate logistic regression modeling found no evidence that any specific demographic factor, clinical outcome or perception/motivation surrounding PGT-A was independently predictive of increased risk for MSR.

LIMITATIONS, REASONS FOR CAUTION

The retrospective nature of data collection incurs the possibility of sampling and recall bias. As only 59% of eligible respondents completed the full survey, it is possible that mainly those with very positive or negative sentiments following treatment felt compelled to complete their response. This bias, however, would apply to the whole of the population, and not simply to those who did or did not complete PGT-A.

WIDER IMPLICATIONS OF THE FINDINGS

The proportion of participants expressing any degree of decision regret in this PGT-A cohort was 40%, which is comparable to that shown in prior research. This study adds to prior data by also assessing decision regret experienced by those who went through IVF without PGT-A, and showed that 68% expressed some level of regret with their decision-making. These results should not be interpreted to mean that all patients should opt for PGT-A to pre-emptively mitigate their risk of regret. Instead, it suggests that drivers of decision regret are likely multifactorial and unique to the experience of one's personal expectations regarding PGT-A, motivations for pursuing or not pursuing it and resultant clinical outcome. Highlighting the complex nature of regret, these data should encourage physicians to more carefully consider individual patient values toward risk-taking or risk-averse behavior, as well as their own positions regarding PGT-A. Until there are clear recommendations regarding utilization of PGT-A, a strong collaboration between physicians and genetic counselors is recommended to educate patients on the risks and potential benefits of PGT-A in a balanced and individualized manner.

STUDY FUNDING/COMPETING INTEREST(S)

No funding was utilized for study completion and the authors have no competing interests.

TRIAL REGISTRATION NUMBER

N/A.

Chromosomal mosaicism: Origins and clinical implications in preimplantation and prenatal diagnosis

The diagnosis of chromosomal mosaicism in the preimplantation and prenatal stage is fraught with uncertainty and multiple factors need to be considered in order to gauge the likely impact. The clinical effects of chromosomal mosaicism are directly linked to the type of the imbalance (size, gene content, and copy number), the timing of the initial event leading to mosaicism during embryogenesis/fetal development, the distribution of the abnormal cells throughout the various tissues within the body as well as the ratio of normal/abnormal cells within each of those tissues. Additional factors such as assay noise and culture artifacts also have an impact on the significance and management of mosaic cases. Genetic counseling is an important part of educating patients about the likelihood of having a liveborn with a chromosome abnormality and these risks differ according to the time of ascertainment and the tissue where the mosaic cells were initially discovered. Each situation needs to be assessed on a case-by-case basis and counseled accordingly. This review will discuss the clinical impact of finding mosaicism through: embryo biopsy, chorionic villus sampling, amniocentesis, and noninvasive prenatal testing using cell-free DNA.

Commentary on two recently published formal guidelines on management of "mosaic" embryos after preimplantation genetic testing for aneuploidy (PGT-A)

Two professional societies recently published opinions on the clinical management of "mosaic" results from preimplantation genetic testing for aneuploidy (PGT-A) in human blastocyst-stage embryos in associations with in vitro fertilization (IVF). We here point out three principal shortcomings: (i) Though a most recent societal opinion states that it should not be understood as an endorsement of the use of PGT-A, any discussion of how PGT-A should be clinically interpreted for all practical purposes does offer such an endorsement. (ii) The same guideline derived much of its opinion from a preceding guidance in favor of utilization of PGT-A that did not follow even minimal professional requirements for establishment of practice guidelines. (iii) Published guidelines on so-called "mosaic" embryos from both societies contradict basic biological characteristics of human preimplantation-stage embryos. They, furthermore, are clinically unvalidated and interpret results of a test, increasingly seen as harmful to IVF outcomes for many infertile women. Qualified professional organizations, therefore, should finally offer transparent guidelines about the utilization of PGT-A in association with IVF in general.

The Technological Advances in Embryo Selection and Genetic Testing: A Look Back at the Evolution of Aneuploidy Screening and the Prospects of Non-Invasive PGT

Since the birth of the first IVF baby, Louise Brown, in 1978, researchers and clinicians have sought ways to improve pregnancy outcomes through embryo selection. In the 1990s, blastomere biopsy and fluorescence in situ hybridization (FISH) were developed in human embryos for the assessment of aneuploidy and translocations. Limitations in the number of chromosomes that could be assayed with FISH lead to the development of comparative genomic hybridization (CGH); however, pregnancy rates overall were not improved. The later development of trophectoderm biopsy with comprehensive chromosome screening (CCS) technologies, as well as the subsequent development of next-generation sequencing (NGS), have shown much greater promise in improving pregnancy and live birth rates. Recently, many studies are focusing on the utilization of non-invasive preimplantation genetic testing (niPGT) in an effort to assess embryo ploidy without exposing embryos to additional interventions.

Preimplantation Genetic Testing for Aneuploidy - a Castle Built on Sand

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

Relationship between age and blastocyst chromosomal ploidy analyzed by noninvasive preimplantation genetic testing for aneuploidies (niPGT-A)

OBJECTIVE

To assess the relationship between human blastocyst chromosomal ploidy established by niPGT-A and increasing age.

METHODS

This is a prospective multicenter study carried out by ten assisted reproduction centers after their embryologists acquired training and validated their results with the previous use of niPGT-A. A total of 94 couples with indication for niPGT-A due to increase maternal age, male factor, repeated implantation failures, recurrent abortion or because they requested niPGT-A were included in this study. The couples had no karyotype abnormalities. After ICSI, the embryos were cultured until blastocyst stage using one or two step culture systems, single or sequential media respectively, at 37°C in an atmosphere of 6-7% CO2 and 5-20% O2 incubators. On day 3, we re-evaluated cleavage embryos to complete cumulus cells removal. The embryos were then cultured in individual well, with 20µl of medium under oil until they reached blastocyst stage. The blastocysts were vitrified and stored in liquid nitrogen. After that, the spent blastocyst culture medium (20µl) was transferred to a PCR tube and sent for analysis in the genetic laboratory, where it was stored at -80°C until sequencing. A total of 243 samples of spent blastocyst culture medium were collected on the 5th/6th day. Cell-free DNA secreted on culture medium was amplified using NICS Sample Preparation Kit (Yikon Genomics), based on the MALBAC technology. After whole genome amplification, the DNA was measured using a Qubit 2.0 fluorometer and subjected to next generation sequencing (NGS) using Illumina MiSeq® platform. The data were analyzed using the ChromGo® software (Yikon Genomics).

RESULTS

The mean age of the patients was 38±4.08 years with an interval of 20-44 years. The euploid was diagnosed in 36.4% (80/220) of cases, aneuploidy in 31.3% (69/220), and mosaicism in 32.3% (71/220; with ≥60% aneuploidy) of blastocysts. Mosaic values ranged from 29.8% to 33.8% in different age groups. Individually, the most frequent chromosomal abnormality was XXY (Klinefelter Syndrome) occurring in 18 cases, followed by chromosome 21 (trisomy/monosomy) in 8 cases. The niPGT-A data showed a ≥60% incidence of aneuploid cells in all cases of chromosomal mosaicism (n=71).

CONCLUSION

A high degree of mosaicism with aneuploidy cells was detected, and some hypotheses were suggested for this data (niPGT-A sensitivity in detecting the self-correction of chromosomal abnormalities phenomenon). However, it did not vary remarkably with age. On the other hand, euploidy levels had a negative correlation with age and aneuploidy levels had a positive relationship. This is the first report in the literature to relate chromosomal ploidy in blastocysts using niPGT-A and increasing patient age.

ROC and AUC with a Binary Predictor: a Potentially Misleading Metric

In analysis of binary outcomes, the receiver operator characteristic (ROC) curve is heavily used to show the performance of a model or algorithm. The ROC curve is informative about the performance over a series of thresholds and can be summarized by the area under the curve (AUC), a single number. When a predictor is categorical, the ROC curve has one less than number of categories as potential thresholds; when the predictor is binary there is only one threshold. As the AUC may be used in decision-making processes on determining the best model, it important to discuss how it agrees with the intuition from the ROC curve. We discuss how the interpolation of the curve between thresholds with binary predictors can largely change the AUC. Overall, we show using a linear interpolation from the ROC curve with binary predictors corresponds to the estimated AUC, which is most commonly done in software, which we believe can lead to misleading results. We compare R, Python, Stata, and SAS software implementations. We recommend using reporting the interpolation used and discuss the merit of using the step function interpolator, also referred to as the "pessimistic" approach by Fawcett (2006).

Healthy live births from transfer of low-mosaicism embryos after preimplantation genetic testing for aneuploidy

PURPOSE

This study evaluated the potential viability of embryos with low mosaicism level (< 50%) by comparing the clinical outcomes of single mosaic versus euploid blastocyst transfer. In addition, the live birth outcomes for various types of mosaicism with respect to abnormalities in chromosome structure and content were analyzed.

METHODS

This study included patients who underwent in vitro fertilization with preimplantation genetic testing for aneuploidy (PGT-A). The PGT-A cycles performed through next-generation sequencing with single euploid or mosaic embryo transfers were included. We collected 299 frozen single embryo transfer cycles-216 single euploid and 83 mosaic-between July 2016 and July 2018. This study analyzed clinical outcomes, including fetal karyotyping by using amniocentesis, gestational age at delivery, and live birth weight after single mosaic embryo transfer.

RESULTS

The average birth weight of infants in the euploid and mosaic blastocyst transfer groups was 3146.2 and 2997.7 g, respectively. The karyotyping results of prenatal diagnosis in all pregnant women were normal. Our study indicated that mosaic embryos can develop into euploid healthy infants with various levels or types of mosaicism. No significant difference was observed between infants from euploid and mosaic blastocyst transfers.

CONCLUSION

If patients have no euploid embryos, mosaic embryos can be transferred as they have potential for implantation and development into euploid healthy infants. This study is invaluable for counseling clinical results after single mosaic embryo transfers.

Optimized NGS Approach for Detection of Aneuploidies and Mosaicism in PGT-A and Imbalances in PGT-SR

The detection of chromosomal aneuploidies and mosaicism degree in preimplantation embryos may be essential for achieving pregnancy. The aim of this study was to determine the robustness of diagnosing homogenous and mosaic aneuploidies using a validated algorithm and the minimal resolution for de novo and inherited deletions and duplications (Del/Dup). Two workflows were developed and validated: (a,b) preimplantation genetic testing for uniform whole and segmental aneuploidies, plus mixtures of euploid/aneuploid genomic DNA to develop an algorithm for detecting mosaicism; and (c) preimplantation genetic testing for structural rearrangements for detecting Del/Dup ≥ 6 Mb. Next-generation sequencing (NGS) was performed with automatic library preparation and multiplexing up to 24-96 samples. Specificity and sensitivity for PGT-A were both 100% for whole chromosomes and segmentals. The thresholds stablished for mosaicism were: euploid embryos (<30% aneuploidy), low mosaic (from 30% to <50%), high mosaic (50-70%) or aneuploid (>70%). In the PGT-SR protocol, changes were made to increase the detection level to ≥6 Mb. This is the first study reporting an accurate assessment of semiautomated-NGS protocols using Reproseq on pools of cells. Both protocols allow for the analysis of homogeneous and segmental aneuploidies, different degrees of mosaicism, and small Del/Dup with high sensitivity and specificity.

Clinical Outcomes of Single Mosaic Embryo Transfer: High-Level or Low-Level Mosaic Embryo, Does it Matter?

Recently, reports showed that embryos identified as mosaic after preimplantation genetic testing for aneuploid (PGT-A) could result in live birth with lower pregnancy and higher pregnancy loss rates compared with euploid embryos. However, the effects of mosaicism level on reproductive outcomes remain controversial. This study aimed to examine the level of mosaicism on pregnancy outcomes. Single mosaic embryo transfer was offered to 108 women who only had mosaic embryos. Mosaic embryos were labeled by utilizing next generation sequencing (NGS) based PGT-A for day 5/6 trophectoderm (TE)biopsies. TE biopsies containing < 50% abnormal cells were classified as low-level mosaicism and ≥ 50% as high-level mosaicism. To further confirm the concordance of chromosome constitution between TE and inner cell mass (ICM), 41 remaining embryos designated as mosaic blastocysts donated for research were also analyzed. Comparable live birth rate (LBR) but higher miscarriage rate (MR) was found in the high-level group. (LBR: low vs. high: 44.5% vs. 36%; p = 0.45, MR: low vs. high: 5.1% vs. 30.7%; p = 0.012). Analyses of TE and ICM from the remaining mosaic blastocysts show a poor concordance. This preliminary study demonstrated that high-level mosaic embryos could result in comparable LBR but higher MR.

The 2019 PGDIS position statement on transfer of mosaic embryos within a context of new information on PGT-A

BACKGROUND

A recently published Position Statement (PS) by the Preimplantation Genetics Diagnosis International Society (PGDIS) regarding utilization of preimplantation genetic testing for aneuploidy (PGT-A) in association with in vitro fertilization (IVF) contained inaccuracies and misrepresentations. Because opinions issued by the PGDIS have since 2016 determined worldwide IVF practice, corrections appear of importance.

METHODS

The International Do No Harm Group in IVF (IDNHG-IVF) is a spontaneously coalesced body of international investigators, concerned with increasing utilization of add-ons to IVF. It is responsible for the presented consensus statement, which as a final document was reached after review of the pertinent literature and again revised after the recent publication of the STAR trial and related commentaries.

RESULTS

In contrast to the PGDIA-PS, we recommend restrictions to the increasing, and by IVF centers now often even mandated, utilization of PGT-A in IVF cycles. While PGT-A has been proposed as a tool for achieving enhanced singleton livebirth outcomes through embryo selection, continued false-positive rates and increasing evidence for embryonic self-correction downstream from the testing stage, has led IDNHG-IVF to conclude that currently available data are insufficient to impose overreaching recommendations for PGT-A utilization.

DISCUSSION

Here presented consensus offers an alternative to the 2019 PGDIS position statement regarding utilization of preimplantation genetic testing for aneuploidy (PGT-A) in association with in vitro fertilization (IVF). Mindful of what appears to offer best outcomes for patients, and in full consideration of patient autonomy, here presented opinion is based on best available evidence, with the goal of improving safety and efficacy of IVF and minimizing wastage of embryos with potential for healthy births.

CONCLUSIONS

As the PGDIS never suggested restrictions on clinical utilization of PGT-A in IVF, here presented rebuttal represents an act of self-regulation by parts of the IVF community in attempts to control increasing utilization of different unproven recent add-ons to IVF.

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

PURPOSE

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Re-analysis of whole blastocysts after trophectoderm biopsy indicated chromosome aneuploidy

Background

To compare the concordance between trophectoderm (TE) analysis and whole blastocyst analysis of embryos from chromosomal structural rearrangement (SR) carriers.

Method

Sixty-three abnormal blastocysts identified by preimplantation genetic testing for chromosomal structural rearrangement (PGT-SR) were included. The whole blastocysts were processed through multiple displacement amplification cycle and sequenced for 24-chromosome aneuploidy screening by next-generation sequencing (NGS). The sequencing results were compared with those of TE biopsy from the same blastocysts and the primary chromosomal rearrangement of the couples.

Results

Analysis of the 63 blastocysts showed 68% (43/63) complete concordance between TE sequencing analysis and whole blastocyst results. Approximately one third (20/63, 32%) of the sequencing results showed some level of discordance between the two samples. Of these, 14% (9/63) of the embryos were identified as euploid after whole blastocyst sequencing. Among them, seven blastocysts were classified as chromosome mosaicism (five whole chromosomes, two segmental) after TE analysis, while two displayed non-SR related segmental changes in the TE biopsy. Of the original analyses, 70% (44/63) of findings were associated with the primary parental chromosomal rearrangement, while 30% (19/63) had no association.

Conclusions

TE biopsy with NGS for PGT-SR is an efficient strategy to identify embryos suitable for transfer. While there was a high concordance between TE and whole blastocyst chromosome results, some embryos classified as mosaic in the original analysis and therefore unsuitable for transfer were reclassified as chromosomally balanced. To maximize the number of embryos available for PGT-SR patients, we suggest that embryos with mosaic non-SR chromosomal rearrangement should be stored and considered for transfer after appropriate counseling.

The mechanisms and clinical application of mosaicism in preimplantation embryos

Embryos containing distinct cell lines are referred to as mosaic embryos, which are considered to be caused by mitotic errors in chromosome segregation during preimplantation development. As the accuracy and resolution of detection techniques improve, more and more mosaic embryos were identified recently. The impacts of mosaic embryos on survival and potential pregnancy outcome have been reported to be diverse in different studies. Because of the universality and clinical significance of mosaicism, it is essential to unravel the mechanisms and consequences with regard to this phenomenon in human pre- and post-implantation embryos. The purpose of this review is to explore the mechanisms, causes of mosaicism, and the development of pre- and post-implantation mosaic embryos in the light of recent emerging data, with the aim of providing new references for clinical applications.

Worldwide live births following the transfer of chromosomally "Abnormal" embryos after PGT/A: results of a worldwide web-based survey

PURPOSE

Preimplantation genetic testing for aneuploidy (PGT-A) has become increasingly controversial since normal euploid births have been reported following transfer of embryos diagnosed as "abnormal." There is an increasing trend in transferring "abnormal" embryos; but it is still unknown how many IVF centers transfer "abnormal" embryos and with what efficiency.

METHODS

We performed a worldwide web-survey of IVF centers to elucidate PGT-A related practice patterns including transfer of human embryos found "abnormal" by PGT-A. Participating centers reflected in vitro fertilization (IVF) cycles in the USA, Canada, Europe, Asia, South America, and Africa.

RESULTS

One hundred fifty-one IVF centers completed the survey; 125 (83%) reported utilization of PGT-A. Europe had the highest utilization (32.3%), followed by the USA and Canada combined at 29.1%. The leading indications for PGT-A were advanced maternal age (77%), followed by recurrent implantation failure (70%), unexplained pregnancy loss (65%), and sex determination (25%); 14% of respondents used PGT-A for all of their IVF cycles; 20% of IVF units reported transfers of chromosomally "abnormal" embryos, and 56% of these took place in the USA, followed by Asia in 20%. Remarkably, 106 (49.3%) cycles resulted in ongoing pregnancies (n = 50) or live births (n = 56). Miscarriages were rare (n = 20; 9.3%).

CONCLUSIONS

The transfers of "abnormal" embryos by PGT-A offered robust pregnancy and live birth chances with low miscarriage rates. These data further strengthen the argument that PGT-A cannot reliably determine which embryos should or should not be transferred and leads to disposal of many normal embryos with excellent pregnancy potential.

National mosaic embryo transfer practices: a survey

BACKGROUND

The growing use of preimplantation genetic testing with in vitro fertilization has provided clinicians with more information about the genetics of embryos. Embryos, however, sometimes result with a mixed composition of both aneuploid and euploid cells, called mosaic embryos. The interpretation of these results has varied, leading some clinicians to transfer mosaic embryos and some opt not to. In addition, laboratories providing preimplantation genetic testing for aneuploidy have differing thresholds for determining an embryo aneuploid, mosaic, or euploid. Overall practice patterns for mosaic embryo transfer practices in the United States are unknown.

OBJECTIVE(S)

The objectives of the study were to characterize national mosaic embryo transfer practices, including the use of preimplantation genetic testing for aneuploidy, prior history of transferring mosaic embryos, thresholds for determining mosaicism, and willingness to transfer mosaic embryos among assisted reproductive technology clinics in the United States.

STUDY DESIGN

A 14 question online survey assessing current use of preimplantation genetic testing for aneuploidy, thresholds for determining mosaicism, and clinic experience and willingness to transfer mosaic embryos was e-mailed to 405 assisted reproductive technology clinics across the United States. Descriptive statistics and logistic regression were used to analyze survey responses and identify clinical factors associated with reporting having ever transferred a mosaic embryo.

RESULTS

Of the 405 US assisted reproductive technology clinics contacted, 252 (62.2%) completed a survey, including 157 private (62.3%), 55 academic (21.8%), and 40 hybrid (15.9%) clinics. Most clinics (168, 66.7%) reported conducting preimplantation genetic testing for aneuploidy on less than 50% of all in vitro fertilization cycles. The most common type of preimplantation genetic testing for aneuploidy technology used was next-generation sequencing at 88.9%. Ninety-one clinics (36.1%) receive mosaicism data on their preimplantation genetic testing for aneuploidy report; the most common thresholds for determining embryo aneuploidy and euploidy by clinics' primary genetics laboratories were <20% normal (36.3%) and >80% normal (46.2%), respectively. Thirty-nine (42.9%) of the 91 have transferred and 57 (62.6%) would transfer a mosaic embryo. Nearly 40% of clinics were unsure about their thresholds for mosaic transfer and one fourth of clinics reported they had no threshold. Private (odds ratio, 1.0, 95% confidence interval, 0.5-1.8) and hybrid (odds ratio, 0.9, 95% confidence interval, 0.4-2.1) clinics were just as likely as academic clinics to report having transferred a mosaic embryo. Clinics in the northeastern United States were more likely to have transferred a mosaic embryo than clinics in other regions (odds ratio, 1.5, 95% confidence interval, 0.9-2.7). Most clinics (72.6%) report they do not have a unique consent for transfer of mosaic embryos.

CONCLUSION

There is uncertainty and variability in the transfer practices of mosaic embryos and classification of mosaicism among US assisted reproductive technology clinics. These findings provide an opportunity to establish mosaicism thresholds and create standardized guidelines for transferring mosaic embryos.

Minimizing mosaicism: assessing the impact of fertilization method on rate of mosaicism after next-generation sequencing (NGS) preimplantation genetic testing for aneuploidy (PGT-A)

PURPOSE

Advances in preimplantation genetic testing (PGT) have led to practice changes in assisted reproductive technologies (ART), enabling fertility centers to transfer single embryos while maintaining excellent ongoing pregnancy rates, reducing miscarriage rates, and dramatically reducing ART-associated multiple pregnancies. The introduction of next-generation sequencing (NGS) allows PGT laboratories to assess for embryo mosaicism-although the true incidence and reproductive potential of predicted mosaic embryos are controversial. Due to concern for genetic contamination from other spermatozoa, most reference laboratories require use of intracytoplasmic sperm injection (ICSI) for single gene preimplantation genetic diagnosis (PGT-M). However, in PGT for aneuploidy (PGT-A), conventional insemination (IVF) is typically permissible. The purpose of this study was to evaluate rates of euploid, aneuploid, and mosaic in trophectoderm biopsy samples from embryos in IVF versus ICSI PGT-A cycles. Secondary aims were to assess sex ratio, and subtypes of aneuploidy and mosaicism in IVF versus ICSI PGT-A cycles.

METHODS

We performed a retrospective review of women undergoing PGT-A at a single academic fertility center from July 1, 2015, to September 1, 2017. In all cycles, PGT-A was performed via trophectoderm biopsy on day 5 or 6 and analyzed using NGS at a single reference lab. We collected and compared patient demographics, fertility testing, cycle characteristics, and PGT-A outcomes between IVF and ICSI cycles.

RESULTS

Three hundred two PGT-A cycles were included for analysis: 75 IVF and 227 ICSI cycles, resulting in 251 IVF and 724 ICSI biopsied blastocysts. Mean oocyte age of included cycles was 38.6 years (IVF) and 38.5 years (ICSI), p = 0.85. Baseline characteristics of IVF and ICSI PGT-A cycles were similar with the exception of semen parameters: IVF cycles had higher sperm concentration and total motility compared to ICSI cycles. PGT-A outcomes did not differ between IVF and ICSI cycles: euploid 27.9% (IVF) versus 30% (ICSI); aneuploid 45.4% (IVF) versus 43.1% (ICSI); no result 4.4% (IVF) versus 6.2% (ICSI). Though not significant, we identified a trend toward higher rate of mosaicism in IVF (25.9%) versus ICSI (20.9%). Among mosaic embryos, a lower percentage of simple mosaic embryos resulted from IVF (53.8%) versus ICSI (70.2%). Among aneuploid embryos, a non-significant higher percentage of complex aneuploidy resulted from IVF (16.3%) versus ICSI (9%). IVF resulted in a non-significant higher proportion of cycles with no transferrable embryos (42.7%) versus ICSI (36.6%). Numerical and sex chromosome involvement in mosaicism and aneuploidy were similar between IVF and ICSI cycles.

CONCLUSION

IVF and ICSI NGS PGT-A have similar rates of euploid, aneuploid, and no result embryos, though IVF may result in higher rates of mosaicism and demonstrates differences in proportions of mosaic and aneuploid subtypes compared to ICSI. ICSI may be preferable to conventional insemination to minimize the rate of mosaic results in NGS PGT-A cycles.

Preimplantation Genetic Testing: Its Evolution, Where Are We Today?

Preimplantation genetic testing (PGT) is an early form of prenatal genetic diagnosis where abnormal embryos are identified, thereby allowing transfer of genetically normal embryos. This technology has become an integral part of Assisted Reproductive Technology (ART) procedures. Initial experiments with animals as early as 1890 and those in the mid and later part of the last century paved the forward path of ART and PGT. This review article covers the evolution of PGT and is a pointer toward current and fast-evolving technology, allowing scientists and doctors to better comprehend human reproduction, and ensure healthy pregnancy outcomes.