Development and validation of a next-generation sequencing–based protocol for 24-chromosome aneuploidy screening of embryos

Non Invasive Preimplantation Testing for Aneuploidies in Assisted Reproduction: A SWOT Analysis

The implementation of non-invasive PGT-A offers a new strategy to genetically assess the preimplantation embryo and to enhance IVF results. The extraction of DNA from the embryo culture medium has been sufficiently demonstrated, and the ability to obtain chromosomal information as a result is particularly interesting. As morphological criteria have proven to have a weak correlation with embryo ploidy status, this technique emerges as a promising alternative for embryo selection. It also appears reasonable that avoiding biopsy may enhance further embryo development. However, there are growing concerns regarding several aspects of this technique, such as the origin of this cell free DNA, the degree of representativeness of the whole embryo, the need for extended culture or the absence of standardized protocols. Despite the published data on good prognosis couples are promising, niPGT-A is yet to be considered a substitute for trophectoderm biopsy. The current SWOT analysis aims to summarize both resolved and unresolved issues, as well as limiting aspects of niPGT-A.

Success rates with preimplantation genetic testing for aneuploidy in good prognosis patients are dependent on age

OBJECTIVE

To evaluate cumulative live birth after preimplantation genetic testing for aneuploidy (PGT-A) with next generation sequencing (NGS) compared with morphology alone among patients aged 21-40 years undergoing single blastocyst transfer.

DESIGN

Retrospective cohort study.

SETTING

Society for Assisted Reproductive Technology (SART) clinics.

PATIENT(S)

Patients aged 21-40 years undergoing first autologous retrieval cycles resulting in ≥5 fertilized oocytes, with subsequent single blastocyst transfer in Society for Assisted Reproductive Technology clinics from 2016-2019.

INTERVENTION

PGT-A using NGS.

MAIN OUTCOME MEASURE(S)

The primary outcome was cumulative live birth per retrieval. Secondary outcomes included clinical pregnancy, miscarriage, and live birth per transfer.

RESULT(S)

A total of 56,469 retrieval cycles were included in the analysis. Retrieval cycles were stratified based on age (<35, 35-37, and 38-40 years) and exposure to PGT-A with NGS. Modified Poisson regression modeling was used to evaluate the association between PGT-A and cumulative live birth per retrieval while controlling for covariates. In this cohort, most cycles did not use PGT-A (n = 49,608; 88%). After adjusting for covariates, the use of PGT-A was associated with a slightly lower cumulative live birth in individuals aged <35 years (risk ratio [RR]: 0.96; 95% CI: 0.93-0.99) compared with no PGT, but higher cumulative live birth in ages 35-37 years (RR: 1.04; 95% CI: 1.00-1.08), and 38-40 years (RR: 1.14; 95% CI: 1.07-1.20). A subgroup analysis limited to freeze-all cycles (n = 29,041) showed that PGT-A was associated with higher cumulative live birth in individuals aged ≥35 years and was similar to no PGT in individuals aged <35 years. Miscarriage was significantly less likely in individuals aged ≥35 years using PGT-A compared with no PGT-A.

CONCLUSION(S)

In this large national database study, success rates in cycles using PGT-A were dependent on age. Cumulative live birth was observed to be significantly less likely in PGT-A cycles among individuals aged <35 years and more likely among individuals aged 38-40 years, compared with no PGT-A. In individuals with no fresh transfer, results were similar. Moreover, miscarriage was significantly less likely with PGT-A among individuals aged 35-40 years in a subgroup analysis of freeze-all cycles.

Preimplantation genetic testing for aneuploidy in patients of different age: a systematic review and meta-analysis

This study aimed to summarize the current knowledge on the benefits of in vitro fertilization/intracytoplasmic sperm injection with preimplantation genetic testing for aneuploidy (PGT-A) and to discuss the role of PGT-A in patients of different ages undergoing assisted reproduction. A systematic review was conducted in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses 2020 checklist. Registration number: CRD42022354697. Studies were identified by searching the PubMed, Cochrane Library, Google Scholar, Scopus, Embase, and ClinicalTrials databases. Seven meta-analyses were performed with additional stratification of age and prognosis of the women studied. Clinical pregnancy rate per embryo transfer in patients aged >35 years was higher in the PGT-A group (P=0.0002) than in controls. Live birth rate (LBR) per embryo transfer in women 35 years old or younger (P=0.002) was higher in the PGT-A group. The LBR per patient in women aged >35 years was higher in the PGT-A group (P=0.004). The effects of PGT-A on LBR in patients with poor prognosis showed a statistically significant increase (P=0.003). There was no significant difference in the rate between the two groups. PGT-A is effective and can be recommended for patients aged >35 years undergoing assisted reproduction to improve their reproductive outcomes. Moreover, our study showed the possible benefits of PGT-A in patients with a poor prognosis. Overall, our findings suggest that PGT-A is a valuable tool for improving the reproductive outcomes of assisted reproductive procedures in older women and those with a history of pregnancy complications.

Preimplantation genetic testing: A narrative review

Preimplantation genetic testing (PGT) is a diagnostic procedure that has become a powerful complement to assisted reproduction techniques. PGT has numerous indications, and there is a wide range of techniques that can be used, each with advantages and limitations that should be considered before choosing the more adequate one. In this article, it is reviewed the indications for PGT, biopsy and diagnostic technologies, along with their evolution, while also broaching new emerging methods.

Preimplantation genetic testing in the current era, a review

BACKGROUND

Preimplantation genetic testing (PGT), also referred to as preimplantation genetic diagnosis (PGD), is an advanced reproductive technology used during in vitro fertilization (IVF) cycles to identify genetic abnormalities in embryos prior to their implantation. PGT is used to screen embryos for chromosomal abnormalities, monogenic disorders, and structural rearrangements.

DEVELOPMENT OF PGT

Over the past few decades, PGT has undergone tremendous development, resulting in three primary forms: PGT-A, PGT-M, and PGT-SR. PGT-A is utilized for screening embryos for aneuploidies, PGT-M is used to detect disorders caused by a single gene, and PGT-SR is used to detect chromosomal abnormalities caused by structural rearrangements in the genome.

PURPOSE OF REVIEW

In this review, we thoroughly summarized and reviewed PGT and discussed its pros and cons down to the minutest aspects. Additionally, recent studies that highlight the advancements of PGT in the current era, including their future perspectives, were reviewed.

CONCLUSIONS

This comprehensive review aims to provide new insights into the understanding of techniques used in PGT, thereby contributing to the field of reproductive genetics.

The mosaic embryo: what it means for the doctor and the patient

INTRODUCTION

Mosaic embryos are embryos that on preimplantation genetic analysis are found to be composed of euploid and aneuploid cells. Although most of these embryos do not implant when transferred into the uterus following IVF treatment, some may implant and are capable of giving rise to babies.

EVIDENCE ACQUISITION

There is currently an increasing number of reports of live births following the transfer of mosaic embryos. Compared to euploid, mosaic embryos have lower implantation rates and higher rates of miscarriage, and occasionally aneuploid component persists. However, their outcome is better than that obtained after the transfer of embryos consisting entirely of aneuploid cells. After implantation, the ability to develop into a full-term pregnancy is influenced by the amount and type of chromosomal mosaicism present in a mosaic embryo. Nowadays many experts in the reproductive field consider mosaic transfers as an option when no euploid embryos are available. Genetic counseling is an important part of educating patients about the likelihood of having a pregnancy with healthy baby but also on the risk that mosaicism could persist and result in liveborn with chromosomal abnormality. Each situation needs to be assessed on a case-by-case basis and counseled accordingly.

EVIDENCE SYNTHESIS

So far, the transfers of 2155 mosaic embryos have been documented and 440 live births resulting in healthy babies have been reported. In addition, in the literature to date, there are 6 cases in which embryonic mosaicism persisted.

CONCLUSIONS

In conclusion, the available data indicate that mosaic embryos have the potential to implant and develop into healthy babies, albeit with lower success rates than euploids. Further clinical outcomes should be collected to better establish a refined ranking of embryos to transfer.

Implicit bias in diagnosing mosaicism amongst preimplantation genetic testing providers: results from a multicenter study of 36 395 blastocysts

STUDY QUESTION

Does the diagnosis of mosaicism affect ploidy rates across different providers offering preimplantation genetic testing for aneuploidies (PGT-A)?

SUMMARY ANSWER

Our analysis of 36 395 blastocyst biopsies across eight genetic testing laboratories revealed that euploidy rates were significantly higher in providers reporting low rates of mosaicism.

WHAT IS KNOWN ALREADY

Diagnoses consistent with chromosomal mosaicism have emerged as a third category of possible embryo ploidy outcomes following PGT-A. However, in the era of mosaicism, embryo selection has become increasingly complex. Biological, technical, analytical, and clinical complexities in interpreting such results have led to substantial variability in mosaicism rates across PGT-A providers and clinics. Critically, it remains unknown whether these differences impact the number of euploid embryos available for transfer. Ultimately, this may significantly affect clinical outcomes, with important implications for PGT-A patients.

STUDY DESIGN, SIZE, DURATION

In this international, multicenter cohort study, we reviewed 36 395 consecutive PGT-A results, obtained from 10 035 patients across 11 867 treatment cycles, conducted between October 2015 and October 2021. A total of 17 IVF centers, across eight PGT-A providers, five countries and three continents participated in the study. All blastocysts were tested using trophectoderm biopsy and next-generation sequencing. Both autologous and donation cycles were assessed. Cycles using preimplantation genetic testing for structural rearrangements were excluded from the analysis.

PARTICIPANTS/MATERIALS, SETTING, METHODS

The PGT-A providers were randomly categorized (A to H). Providers B, C, D, E, F, G, and H all reported mosaicism, whereas Provider A reported embryos as either euploid or aneuploid. Ploidy rates were analyzed using multilevel mixed linear regression. Analyses were adjusted for maternal age, paternal age, oocyte source, number of embryos biopsied, day of biopsy, and PGT-A provider, as appropriate. We compared associations between genetic testing providers and PGT-A outcomes, including the number of chromosomally normal (euploid) embryos determined to be suitable for transfer.

MAIN RESULTS AND THE ROLE OF CHANCE

The mean maternal age (±SD) across all providers was 36.2 (±5.2). Our findings reveal a strong association between PGT-A provider and the diagnosis of euploidy and mosaicism. Amongst the seven providers that reported mosaicism, the rates varied from 3.1% to 25.0%. After adjusting for confounders, we observed a significant difference in the likelihood of diagnosing mosaicism across providers (P < 0.001), ranging from 6.5% (95% CI: 5.2-7.4%) for Provider B to 35.6% (95% CI: 32.6-38.7%) for Provider E. Notably, adjusted euploidy rates were highest for providers that reported the lowest rates of mosaicism (Provider B: euploidy, 55.7% (95% CI: 54.1-57.4%), mosaicism, 6.5% (95% CI: 5.2-7.4%); Provider H: euploidy, 44.5% (95% CI: 43.6-45.4%), mosaicism, 9.9% (95% CI: 9.2-10.6%)); and Provider D: euploidy, 43.8% (95% CI: 39.2-48.4%), mosaicism, 11.0% (95% CI: 7.5-14.5%)). Moreover, the overall chance of having at least one euploid blastocyst available for transfer was significantly higher when mosaicism was not reported, when we compared Provider A to all other providers (OR = 1.30, 95% CI: 1.13-1.50). Differences in diagnosing and interpreting mosaic results across PGT-A laboratories raise further concerns regarding the accuracy and relevance of mosaicism predictions. While we confirmed equivalent clinical outcomes following the transfer of mosaic and euploid blastocysts, we found that a significant proportion of mosaic embryos are not used for IVF treatment.

LIMITATIONS, REASONS FOR CAUTION

Due to the retrospective nature of the study, associations can be ascertained, however, causality cannot be established. Certain parameters such as blastocyst grade were not available in the dataset. Furthermore, certain platform-related and clinic-specific factors may not be readily quantifiable or explicitly captured in our dataset. As such, a full elucidation of all potential confounders accounting for variability may not be possible.

WIDER IMPLICATIONS OF THE FINDINGS

Our findings highlight the strong need for standardization and quality assurance in the industry. The decision not to transfer mosaic embryos may ultimately reduce the chance of success of a PGT-A cycle by limiting the pool of available embryos. Until we can be certain that mosaic diagnoses accurately reflect biological variability, reporting mosaicism warrants utmost caution. A prudent approach is imperative, as it may determine the difference between success or failure for some patients.

STUDY FUNDING/COMPETING INTEREST(S)

This work was supported by the Torres Quevedo Grant, awarded to M.P. (PTQ2019-010494) by the Spanish State Research Agency, Ministry of Science and Innovation, Spain. M.P., L.B., A.R.L., A.L.R.d.C.L., N.P.P., M.P., D.S., F.A., A.P., B.M., L.D., F.V.M., D.S., M.R., E.P.d.l.B., A.R., and R.V. have no competing interests to declare. B.L., R.M., and J.A.O. are full time employees of IB Biotech, the genetics company of the Instituto Bernabeu group, which performs preimplantation genetic testing. M.G. is a full time employee of Novagen, the genetics company of Cegyr, which performs preimplantation genetic testing.

TRIAL REGISTRATION NUMBER

N/A.

Embryo drop-out rates in preimplantation genetic testing for aneuploidy (PGT-A): a retrospective data analysis from the DoLoRes study

PURPOSE

To evaluate the decline in transferable embryos in preimplantation genetic testing for aneuploidy (PGT-A) cycles due to (a) non-biopsable blastocyst quality, (b) failure of genetic analysis, (c) diagnosis of uniform numerical or structural chromosomal aberrations, and/or (d) chromosomal aberrations in mosaic constitution.

METHODS

This retrospective multicenter study comprised outcomes of 1562 blastocysts originating from 363 controlled ovarian stimulation cycles, respectively, 226 IVF couples in the period between January 2016 and December 2018. Inclusion criteria were PGT-A cycles with trophectoderm biopsy (TB) and next generation sequencing (NGS).

RESULTS

Out of 1562 blastocysts, 25.8% were lost due to non-biopsable and/or non-freezable embryo quality. In 10.3% of all biopsied blastocysts, genetic analysis failed. After exclusion of embryos with uniform or chromosomal aberrations in mosaic, only 18.1% of those originally yielded remained as diagnosed euploid embryos suitable for transfer. This translates into 50.4% of patients and 57.6% of stimulated cycles with no euploid embryo left for transfer. The risk that no transfer can take place rose significantly with a lower number of oocytes and with increasing maternal age. The chance for at least one euploid blastocyst/cycle in advanced maternal age (AMA)-patients was 33.3% compared to 52.1% in recurrent miscarriage (RM), 59.8% in recurrent implantation failure (RIF), and 60.0% in severe male factor (SMF).

CONCLUSIONS

The present study demonstrates that PGT-A is accompanied by high embryo drop-out rates. IVF-practitioners should be aware that their patients run a high risk of ending up without any embryo suitable for transfer after (several) stimulation cycles, especially in AMA patients. Patients should be informed in detail about the frequency of inconclusive or mosaic results, with the associated risk of not having an euploid embryo available for transfer after PGT-A, as well as the high cost involved in this type of testing.

Scalable noninvasive amplicon-based precision sequencing (SNAPseq) for genetic diagnosis and screening of β-thalassemia and sickle cell disease using a next-generation sequencing platform

β-hemoglobinopathies such as β-thalassemia (BT) and Sickle cell disease (SCD) are inherited monogenic blood disorders with significant global burden. Hence, early and affordable diagnosis can alleviate morbidity and reduce mortality given the lack of effective cure. Currently, Sanger sequencing is considered to be the gold standard genetic test for BT and SCD, but it has a very low throughput requiring multiple amplicons and more sequencing reactions to cover the entire HBB gene. To address this, we have demonstrated an extraction-free single amplicon-based approach for screening the entire β-globin gene with clinical samples using Scalable noninvasive amplicon-based precision sequencing (SNAPseq) assay catalyzing with next-generation sequencing (NGS). We optimized the assay using noninvasive buccal swab samples and simple finger prick blood for direct amplification with crude lysates. SNAPseq demonstrates high sensitivity and specificity, having a 100% agreement with Sanger sequencing. Furthermore, to facilitate seamless reporting, we have created a much simpler automated pipeline with comprehensive resources for pathogenic mutations in BT and SCD through data integration after systematic classification of variants according to ACMG and AMP guidelines. To the best of our knowledge, this is the first report of the NGS-based high throughput SNAPseq approach for the detection of both BT and SCD in a single assay with high sensitivity in an automated pipeline.

Investigation of the risk of paternal cell contamination in PGT and the necessity of intracytoplasmic sperm injection

ICSI is widely recommended for patients undergoing preimplantation genetic testing (PGT), but are sperm a potential source of paternal cell contamination in PGT? Semen samples were obtained from five normozoospermic men consenting to research. From each sample 1, 2, 4, 8 and 10 sperm were collected in PCR tubes and whole genome amplification according to PGT-A and PGT-SR processing protocols was undertaken. None of the 25 samples submitted (a total of 125 sperm) showed evidence of DNA amplification. Thus, paternal cell contamination resulting from using conventional in vitro fertilization (IVF) as the insemination method, carries a low risk of an adverse event or misdiagnosis in PGT-A. Due to the higher risk incurred with PGT-SR, clinics may wish to exercise increased caution and continue using ICSI, while PGT-M involves different processing protocols, presenting a different risk profile.

A study of application effects of next-generation sequencing based preimplantation genetic testing for aneuploidies in advanced maternal age women

OBJECTIVE

To investigate if next-generation sequencing-based preimplantation genetic testing for aneuploidies could improve pregnancy outcomes in women of advanced maternal age.

MATERIALS AND METHODS

A retrospective analysis. The clinical data of 1099 couples treated in the First Medical Center of the Chinese PLA General Hospital from January 2019 to December 2021 were analyzed. They were divided into two groups based on whether they underwent a Next-generation sequencing-based preimplantation genetic test for aneuploidies. We analyzed and compared the biochemical pregnancy rate, clinical pregnancy rate, abortion rate, and live birth rate between the two groups.

RESULTS

The Preimplantation genetic testing for aneuploidies (PGT-A) group was associated with higher rate of biochemical pregnancy and clinical pregnancy than the non-PGT-A group, which were 63.9% vs. 56.4% (P = 0.009) and 54.4% vs. 45.6% (P < 0.001), respectively. The abortion rate was significantly lower in the PGT-A group compared to the non-PGT-A group (2.3% vs. 14.7%, P < 0.001). In addition, the live birth rate was significantly higher in the PGT-A group compared to the non-PGT-A group (52.1% and 30.9%, respectively, P < 0.001).

CONCLUSION

Next-generation sequencing-based preimplantation genetic testing for aneuploidies significantly improved the pregnancy outcomes in women of advanced maternal age.

Randomised double-blind controlled trial of non-invasive preimplantation genetic testing for aneuploidy in in vitro fertilisation: a protocol paper

INTRODUCTION

The success rate of in vitro fertilisation (IVF) treatment for couples with infertility remains low due to lack of a reliable tool in selecting euploid embryos for transfer. This study aims to compare the efficacy in embryo selection based on morphology alone compared with non-invasive preimplantation genetic testing for aneuploidy (niPGT-A) and morphology in infertile women undergoing IVF.

METHODS AND ANALYSIS

This is a randomised double-blind controlled trial conducted in two tertiary assisted reproduction centres. A total of 500 infertile women will be recruited and undergo IVF as indicated. They will be randomly assigned on day 6 after oocyte retrieval into two groups: the intervention group using morphology and niPGT-A and the control group based on morphology alone. In the control group, blastocysts with the best quality morphology will be replaced first. In the intervention group, blastocysts with the best morphology and euploid result of spent culture medium will be replaced first. The primary outcome is a live birth per the first embryo transfer. The statistical analysis will be performed with the intention to treat and per protocol.

ETHICS AND DISSEMINATION

Ethics approval was sought from the institutional review board of the two participating units. All participants will provide written informed consent before joining the study. The results of the study will be submitted to scientific conferences and peer-reviewed journals.

TRIAL REGISTRATION NUMBER

NCT04474522.

Trophectoderm biopsy is associated with adverse obstetric outcomes rather than neonatal outcomes

BACKGROUND

With the wide application of preimplantation genetic testing (PGT) with trophectoderm (TE) biopsy, the safety of PGT has always been a concern. Since TE subsequently forms the placenta, it is speculated that the removal of these cells was associated with adverse obstetrical or neonatal outcomes after single frozen-thawed blastocyst transfer (FBT). Previous studies report contradictory findings with respect to TE biopsy and obstetric and neonatal outcomes.

METHODS

We conducted a retrospective cohort study including 720 patients with singleton pregnancies from single FBT cycles who delivered at the same university-affiliated hospital between January 2019 and March 2022. The cohorts were divided into two groups: the PGT group (blastocysts with TE biopsy, n = 223) and the control group (blastocysts without biopsy, n = 497). The PGT group was matched with the control group by propensity score matching (PSM) analysis at a ratio of 1:2. The enrolled sample sizes in the two groups were 215 and 385, respectively.

RESULTS

Patient demographic characteristics were comparable between the groups after PSM except for the proportion of recurrent pregnancy loss, which was significantly higher in the PGT cohort (31.2 vs. 4.2%, P < 0.001). Patients in the PGT group had significantly higher rates of gestational hypertension (6.0 vs. 2.6%, adjusted odds ratio (aOR) 2.91, 95% confidence interval (CI) 1.18-7.18, P = 0.020) and abnormal umbilical cord (13.0 vs. 7.8%, aOR 1.94, 95% CI 1.08-3.48, P = 0.026). However, the occurrence of premature rupture of membranes (PROM) (12.1 vs. 19.7%, aOR 0.59, 95% CI 0.35-0.99, P = 0.047) was significantly lower in biopsied blastocysts than in unbiopsied embryos. There were no significant differences in regard to other obstetric and neonatal outcomes between the two groups.

CONCLUSIONS

Trophectoderm biopsy is a safe approach, as the neonatal outcomes from biopsied and unbiopsied embryos were comparable. Furthermore, PGT is associated with higher risks of gestational hypertension and abnormal umbilical cord but may have a protective effect on PROM.

Reduced mitochondrial DNA content correlate with poor clinical outcomes in cryotransfers with day 6 single euploid embryos

Objective

To investigate whether the mitochondrial DNA (mtDNA) content of a single biopsy at trophoblast correlates with the developmental potential and reproductive outcomes of blastocyst.

Methods

A retrospective analysis applied the dataset of 1,675 embryos with preimplantation genetic testing for aneuploidy (PGT-A) from 1,305 individuals, and 1,383 embryos involved cryotransfers of single euploid embryo between January 2015 and December 2019. The studied cohort was divided for algorithm establishment on the NGS platform (n=40), correlation of biological features (n=1,635), and correlation of reproductive outcomes (n=1,340). Of the algorithm derived from the NGS platform, the reliability and repeatability were validated via qPCR assay and inter-run controls, respectively. Of the correlation across biological features, stratification analyses were applied to evaluate the effect from a single contributor. Eventually, the correlation between the mtDNA ratios and reproductive outcomes was adjusted according to the significant effector(s).

Results

The mtDNA ratios showed statistically different between embryos with different days of blastocyst formation ([Day 5]: 1.06 vs. [Day 6]: 0.66, p=0.021), and between embryos with different expansion stages ([Expansion 5]: 1.05 vs. [Expansion 6]: 0.49, p=0.012). None or weakly correlated with the maternal age, morphology, ploidy, and gender. Analyzed by the different days of blastocyst formation with fixed expansion score as 5 in the euploid single embryo transfers (eSET), the day 6 eSET showed significantly lower reduced mtDNA ratio (n=139) in failure groups of fetal heartbeat (p=0.004), ongoing pregnancy (p=0.007), and live birth (p=0.01); however, no correlation between mtDNA ratios and pregnancy outcomes was observed in the day 5 eSET (n=1,201).

Conclusions

The study first demonstrated that mtDNA ratio was dependent on the days of blastocyst formation while expansion stage was fixed. Lower mtDNA ratios were observed in the day 6 eSET with adverse outcomes. The present stratification analyses reveal that the timeline of embryo is an important covariate to the mtDNA content.

The number and rate of euploid blastocysts in women undergoing IVF/ICSI cycles are strongly dependent on ovarian reserve and female age

STUDY QUESTION

Can the possibility of having at least one euploid blastocyst for embryo transfer and the total number of euploid blastocysts be predicted for couples before they enter the IVF programme?

SUMMARY ANSWER

Ovarian reserve and female age are the most important predictors of having at least one euploid blastocyst and the total number of euploid blastocysts.

WHAT IS KNOWN ALREADY

The blastocyst euploidy rate among women undergoing ART has already been shown to significantly decrease with increasing female age, and the total number of euploid embryos is dependent on the blastocyst cohort size. However, the vast majority of published studies are based on retrospective analysis of data.

STUDY DESIGN, SIZE, DURATION

This prospective analysis included 847 consecutively enrolled couples approaching their first preimplantation genetic testing for aneuploidies (PGT-A) cycle between 2017 and 2020. Only couples for whom ejaculated sperm was available and women with a BMI of <35 kg/m2 were included in the study. Only the first cycle was included for each patient.

PARTICIPANTS/MATERIALS, SETTING, METHODS

The study was conducted at an IVF centre where, for all patients, the planned treatment was to obtain embryos at the blastocyst stage for the PGT-A programme. The impact of the following covariates was investigated: a woman's serum AMH level, age, height, weight and BMI and a man's age, height, weight, BMI, sperm volume and sperm motility and morphology. The analysis was performed with a machine learning (ML) approach. Models were fit on the training set (677 patients) and their predictive performance was then evaluated on the test set (170 patients).

MAIN RESULTS AND ROLE OF CHANCE

After ovarian stimulation and oocyte insemination, 40.1% of couples had at least one blastocyst available for the PGT-A. Of 1068 blastocysts analysed, 33.6% were euploid. Two distinct ML models were fit: one for the probability of having at least one euploid blastocyst and one for the number of euploid blastocysts obtained. In the training set of patients, the variable importance plots of both models indicated that AMH and the woman's age are by far the most important predictors. Specifically, a positive association between the outcome and AMH and a negative association between the outcome and female age appeared. Gradient-boosted modelling offers a greater predictive performance than generalized additive models (GAMs).

LIMITATIONS, REASONS FOR CAUTION

The study was performed based on data from a single centre. While this provides a robust set of data with a constant ART process and laboratory practice, the model might be suitable only for the evaluated population, which may limit the generalization of the model to other populations.

WIDER IMPLICATIONS OF THE FINDINGS

ML models indicate that for couples entering the IVF/PGT-A programme, ovarian reserve, which is known to vary with age, is the most important predictor of having at least one euploid embryo. According to the GAM, the probability of a 30-year-old woman having at least one euploid embryo is 28% or 47% if her AMH level is 1 or 3 ng/ml, respectively; if the woman is 40 years old, this probability is 18% with an AMH of 1 ng/ml and 30% with an AMH of 3 ng/ml.

STUDY FUNDING/COMPETING INTEREST(S)

This study was supported by an unrestricted grant from Gedeon Richter. The authors declared no conflict of interests.

TRIAL REGISTRATION NUMBER

N/A.

On the origins and fate of chromosomal abnormalities in human preimplantation embryos: an unsolved riddle

About 8 out of 10 human embryos obtained in vitro harbour chromosomal abnormalities of either meiotic or mitotic origin. Abnormalities of mitotic origin lead to chromosomal mosaicism, a phenomenon which has sparked much debate lately as it confounds results obtained through preimplantation genetic testing for aneuploidy (PGT-A). PGT-A in itself is still highly debated, not only on the modalities of its execution, but also on whether it should be offered to patients at all.

We will focus on post-zygotic chromosomal abnormalities leading to mosaicism. First, we will summarize what is known of the rates of chromosomal abnormalities at different developmental stages. Next, based on the current understanding of the origin and cellular consequences of chromosomal abnormalities, which is largely based on studies on cancer cells and model organisms, we will offer a number of hypotheses on which mechanisms may be at work in early human development. Finally, and very briefly, we will touch upon the impact our current knowledge has on the practice of PGT-A. What is the level of abnormal cells that an embryo can tolerate before it loses its potential for full development? And is blastocyst biopsy as harmless as it seems?

Mitochondrial DNA Copy Number in Cleavage Stage Human Embryos-Impact on Infertility Outcome

A retrospective case control study was undertaken at the molecular biology department of a private center for reproductive medicine in order to determine whether any correlation exists between mitochondrial DNA (mtDNA) content of cleavage-stage preimplantation embryos and their developmental potential. A total of 69 couples underwent IVF treatment (averaged women age: 36.5, SD 4.9) and produced a total of 314 embryos. A single blastomere was biopsied from each embryo at the cleavage stage (day-3 post-fertilization) subjected to low-pass next generation sequencing (NGS), for the purpose of detecting aneuploidy. For each sample, the number of mtDNA reads obtained after analysis using NGS was divided by the number of reads attributable to the nuclear genome. The mtDNA copy number amount was found to be higher in aneuploid embryos than in those that were euploid (mean mtDNA ratio ± SD: 6.3 ± 7.5 versus 7.1 ± 5.8, p < 0.004; U Mann−Whitney test), whereas no statistically significant differences in mtDNA content were seen in relation to embryo morphology (6.6 ± 4.8 vs. 8.5 ± 13.6, p 0.09), sex (6.6 ± 4.1 vs. 6.2 ± 6.8, p 0.16), maternal age (6.9 ± 7.8 vs. 6.7 ± 4.5, p 0.14) or its ability to implant (7.4 ± 6.6 vs. 5.1 ± 4.6, p 0.18). The mtDNA content cannot serve as a useful biomarker at this point in development. However, further studies investigating both quantitative and qualitative aspects of mtDNA are still required to fully evaluate the relationship between mitochondrial DNA and human reproduction.

In vitro propagation of XXY human Klinefelter spermatogonial stem cells: A step towards new fertility opportunities

Klinefelter Syndrome (KS) is characterized by a masculine phenotype, supernumerary sex chromosomes (47, XXY), and impaired fertility due to loss of spermatogonial stem cells (SSCs). Early testicular cryopreservation could be an option for future fertility treatments in these patients, including SSCs transplantation or in vitro spermatogenesis. It is critically essential to adapt current in vitro SSCs propagation systems as a fertility option for KS patients. KS human testicular samples (13,15- and 17-year-old non-mosaic KS boys) were donated by patients enrolled in an experimental testicular tissue banking program. Testicular cells were isolated from cryopreserved tissue and propagated in long-term culture for 110 days. Cell-specific gene expression confirmed the presence of all four main cell types found in testes: Spermatogonia, Sertoli, Leydig, and Peritubular cells. A population of ZBTB16⁺ undifferentiated spermatogonia was identified throughout the culture using digital PCR. Flow cytometric analysis also detected an HLA^-/CD9⁺/CD49f⁺ population, indicating maintenance of a stem cell subpopulation among the spermatogonial cells. FISH staining for chromosomes X and Y showed most cells containing an XXY karyotype with a smaller number containing either XY or XX. Both XY and XX populations were able to be enriched by magnetic sorting for CD9 as a spermatogonia marker. Molecular karyotyping demonstrated genomic stability of the cultured cells, over time. Finally, single-cell RNAseq analysis confirmed transcription of ID4, TCN2, and NANOS 3 within a population of putative SSCs population. This is the first study showing successful isolation and long-term in vitro propagation of human KS testicular cells. These findings could inform the development of therapeutic fertility options for KS patients, either through in vitro spermatogenesis or transplantation of SSC, in vivo.

High concordance in preimplantation genetic testing for aneuploidy between automatic identification via Ion S5 and manual identification via Miseq

The Ion S5 (Thermo Fisher Scientific) and Miseq (Illumina) NGS systems are both widely used in the clinical laboratories conducting PGT-A. Each system employs discrepant library preparation steps, sequencing principles, and data processing algorithms. The automatic interpretation via Ion Reporter software (Thermo Fisher Scientific) and the manual interpretation via BlueFuse Multi software (Illumina) for chromosomal copy number variation (CNV) represent very different reporting approaches. Thus, it is intriguing to compare their ability of ploidy detection as PGT-A/NGS system. In the present study, four aneuploid cell lines were individually mixed with a diploid cell line at different aneuploid ratios of 0% (0:5), 10% (1:9), 20% (1:4), 40% (2:3), 50% (3:3), 60% (3:2), 80% (4:1) and 100% (5:0) to assess the sensitivity and specificity for whole chromosomal and segmental aneuploidy detection. The clinical biopsies of 107 blastocysts from 46 IVF/PGT-A cycles recruited between December 2019 and February 2020 were used to calculate the concordance. Initially, the pre-amplified products were divided into two aliquots for different library preparation procedures of each system. Applying the same calling criteria, automatic identification was achieved through the Ion Reporter, while well-trained technicians manually identified each sample through the BlueFuse Multi. The results displayed that both systems reliably distinguished chromosomal CNV of the mixtures with at least 10% aneuploidy from karyotypically normal samples ([Ion S5] whole-chromosomal duplication: 2.14 vs. 2.05, p value = 0.009, segmental deletion: 1.88 vs. 2.05, p value = 0.003; [Miseq] whole-chromosomal duplication: 2.12 vs. 2.03, p value = 0.047, segmental deletion: 1.82 vs. 2.03, p value = 0.002). The sensitivity and specificity were comparable between the Ion S5 and Miseq ([sensitivity] 93% vs. 90%, p = 0.78; [specificity] 100% vs. 100%, p value = 1.0). In the 107 clinical biopsies, three displayed chaotic patterns (2.8%), which could not be interpreted for the ploidy. The ploidy concordance was 99.04% (103/104) per embryo and 99.47% (2265/2277) per chromosome pair. Since their ability of detection were proven to be similar, the automatic identification in Ion S5 system presents comparatively faster and more standardized performance.

Different Strategies of Preimplantation Genetic Testing for Aneuploidies in Women of Advanced Maternal Age: A Systematic Review and Meta-Analysis

Background: Preimplantation genetic testing for aneuploidies (PGT-A) is widely used in women of advanced maternal age (AMA). However, the effectiveness remains controversial. Method: We conducted a comprehensive literature review comparing outcomes of IVF with or without PGT-A in women of AMA in PubMed, Embase, and the Cochrane Central Register of Controlled Trials in January 2021. All included trials met the criteria that constituted a randomized controlled trial for PGT-A involving women of AMA (≥35 years). Reviews, conference abstracts, and observational studies were excluded. The primary outcome was the live birth rate in included random control trials (RCTs). Results: Nine randomized controlled trials met our inclusion criteria. For techniques of genetic analysis, three trials (270 events) performed with comprehensive chromosomal screening showed that the live birth rate was significantly higher in the women randomized to IVF/ICSI with PGT-A (RR = 1.30, 95% CI 1.03–1.65), which was not observed in six trials used with FISH as well as all nine trials. For different stages of embryo biopsy, only the subgroup of blastocyst biopsy showed a higher live birth rate in women with PGT-A (RR = 1.36, 95% CI 1.04–1.79). Conclusion: The application of comprehensive chromosome screening showed a beneficial effect of PGT-A in women of AMA compared with FISH. Moreover, blastocyst biopsy seemed to be associated with a better outcome than polar body biopsy and cleavage-stage biopsy.

Factors associated with vitrification-warming survival in 6167 euploid blastocysts

PURPOSE

To understand the clinical factors associated with embryo survival after vitrification in a cohort of human blastocysts screened by preimplantation genetic testing for aneuploidy (PGT-A).

METHODS

Patient demographic, embryo, and cycle characteristics associated with failed euploid blastocyst survival were compared in a cohort of women (n = 6167) who underwent IVF-PGT-A.

RESULTS

Compared to those that survived warming, vitrified euploid embryos that failed to survive after warming came from IVF cycles with significantly higher estradiol levels at time of surge (2754.8 ± 1390.2 vs. 2523.1 ± 1190.6 pg/mL, p = 0.03), number of oocytes retrieved (19.6 ± 10.7 vs. 17.5 ± 9.8, p = 0.005), and basal antral follicle count (BAFC) (15.3 ± 8.5 vs. 13.9 ± 7.2, p = 0.05). Euploid embryos were less likely to survive warming if they came from cycles before 2015 (24.6% vs. 13.2%, p < 0.001), were cryopreserved on day 7 versus day 5 or 6 (9.1% vs. 3.0%, p < 0.001), underwent two trophectoderm biopsies (6.9% vs. 2.3%, p < 0.001), had a grade C inner cell mass (15.4% vs. 7.7%, p < 0.001), or were fully hatched (41.1% vs. 12.2%, p < 0.001). In the multivariate model, which controlled for relevant confounders, the association between decreased survival and increased BAFC, year of IVF cycle, double trophectoderm biopsy, and fully hatched blastocysts remained statistically significant.

CONCLUSION

Euploid embryos that are fully hatched at time of vitrification, come from patients with high ovarian reserve, or require repeat trophectoderm biopsy are less likely to survive vitrification-warming. Our results provide a framework for reproductive counseling and offer realistic expectations to patients about the number of embryos needed to achieve family building goals.

Experience analysing over 190,000 embryo trophectoderm biopsies using a novel FAST-SeqS preimplantation genetic testing assay

RESEARCH QUESTION

Is FAST-SeqS an accurate methodology for preimplantation genetic testing for whole-chromosome aneuploidy (PGT-A)? What additional types of chromosomal abnormalities can be assessed? What are the observed aneuploidy rates in a large clinical cohort?

DESIGN

FAST-SeqS, a next-generation sequencing (NGS)-based assay amplifying genome-wide LINE1 repetitive sequences, was validated using reference samples. Sensitivity and specificity were calculated. Clinically derived trophectoderm biopsies submitted for PGT-A were assessed, and aneuploidy and mosaicism rates among biopsies were determined. Clinician-provided outcome rates were calculated.

RESULTS

Sensitivity and specificity were over 95% for all aneuploidy types tested in the validation. Comparison of FAST-SeqS with VeriSeq showed high concordance (98.5%). Among embryos with actionable results (n = 182,827), 46.2% were aneuploid. Whole-chromosome aneuploidies were most observed (72.9% without or 8.7% with a segmental aneuploidy), with rates increasing with egg age; segmental aneuploidy rates did not. Segmental aneuploidy (n = 20,557) was observed on all chromosomes (most commonly deletions), with frequencies associated with chromosome length. Mosaic-only abnormalities constituted 10.1% (n = 3862/38145) of samples. Abnormal ploidy constituted 1.8% (n = 2370/128,991) of samples, triploidy being the most common (73.6%). Across 3297 frozen embryo transfers, the mean clinical pregnancy rate was 62% (range 38-80%); the mean combined ongoing pregnancy and live birth rate was 57% (range 38-72%).

CONCLUSION

FAST-SeqS is a clinically reliable and scalable method for PGT-A, is comparable to whole-genome amplification-based platforms, and detects additional information related to ploidy using SNP analysis. Results suggest ongoing benefit of PGT-A using FAST-SeqS, consistent with other platforms.

Progress and Challenges in Laboratory-Based Diagnostic and Screening Approaches for Aneuploidy Detection during Pregnancy

Aneuploidy is caused by problems during cellular division and segregation errors during meiosis that lead to an abnormal number of chromosomes and initiate significant genetic abnormalities during pregnancy or the loss of a fetus due to miscarriage. Screening and diagnostic technologies have been developed to detect this genetic condition and provide parents with critical information about their unborn child. In this review, we highlight the complexities of aneuploidy as a disease as well as multiple technological advancements in testing that help to identify aneuploidy at various time points throughout pregnancy. We focus on aneuploidy diagnosis during preimplantation genetic testing that is performed during in vitro fertilization as well as prenatal screening and diagnosis during pregnancy. This review focuses on DNA-based analysis and laboratory techniques for aneuploidy detection through reviewing molecular- and engineering-based technical advancements. We also present key challenges in aneuploidy detection during pregnancy, including sample collection, mosaic embryos, economic factors, and the social implications of this testing. The goal of this review is to synthesize broad information about aneuploidy screening and diagnostic sample collection and analysis during pregnancy and discuss major challenges the field is still facing despite decades of advancements.

Comprehensive preimplantation genetic testing by massively parallel sequencing

STUDY QUESTION

Can whole genome sequencing (WGS) offer a relatively cost-effective approach for embryonic genome-wide haplotyping and preimplantation genetic testing (PGT) for monogenic disorders (PGT-M), aneuploidy (PGT-A) and structural rearrangements (PGT-SR)?

SUMMARY ANSWER

Reliable genome-wide haplotyping, PGT-M, PGT-A and PGT-SR could be performed by WGS with 10× depth of parental and 4× depth of embryonic sequencing data.

WHAT IS KNOWN ALREADY

Reduced representation genome sequencing with a genome-wide next-generation sequencing haplarithmisis-based solution has been verified as a generic approach for automated haplotyping and comprehensive PGT. Several low-depth massively parallel sequencing (MPS)-based methods for haplotyping and comprehensive PGT have been developed. However, an additional family member, such as a sibling, or a proband, is required for PGT-M haplotyping using low-depth MPS methods.

STUDY DESIGN, SIZE, DURATION

In this study, 10 families that had undergone traditional IVF-PGT and 53 embryos, including 13 embryos from two PGT-SR families and 40 embryos from eight PGT-M families, were included to evaluate a WGS-based method. There were 24 blastomeres and 29 blastocysts in total. All embryos were used for PGT-A. Karyomapping validated the WGS results. Clinical outcomes of the 10 families were evaluated.

PARTICIPANTS/MATERIALS, SETTING, METHODS

A blastomere or a few trophectoderm cells from the blastocyst were biopsied, and multiple displacement amplification (MDA) was performed. MDA DNA and bulk DNA of family members were used for library construction. Libraries were sequenced, and data analysis, including haplotype inheritance deduction for PGT-M and PGT-SR and read-count analysis for PGT-A, was performed using an in-house pipeline. Haplotyping with a proband and parent-only haplotyping without additional family members were performed to assess the WGS methodology. Concordance analysis between the WGS results and traditional PGT methods was performed.

MAIN RESULTS AND THE ROLE OF CHANCE

For the 40 PGT-M and 53 PGT-A embryos, 100% concordance between the WGS and single-nucleotide polymorphism (SNP)-array results was observed, regardless of whether additional family members or a proband was included for PGT-M haplotyping. For the 13 embryos from the two PGT-SR families, the embryonic balanced translocation was detected and 100% concordance between WGS and MicroSeq with PCR-seq was demonstrated.

LIMITATIONS, REASONS FOR CAUTION

The number of samples in this study was limited. In some cases, the reference embryo for PGT-M or PGT-SR parent-only haplotyping was not available owing to failed direct genotyping.

WIDER IMPLICATIONS OF THE FINDINGS

WGS-based PGT-A, PGT-M and PGT-SR offered a comprehensive PGT approach for haplotyping without the requirement for additional family members. It provided an improved complementary method to PGT methodologies, such as low-depth MPS- and SNP array-based methods.

STUDY FUNDING/COMPETING INTEREST(S)

This research was supported by the research grant from the National Key R&D Program of China (2018YFC0910201 and 2018YFC1004900), the Guangdong province science and technology project of China (2019B020226001), the Shenzhen Birth Defect Screening Project Lab (JZF No. [2016] 750) and the Shenzhen Municipal Government of China (JCYJ20170412152854656). This work was also supported by the National Natural Science Foundation of China (81771638, 81901495 and 81971344), the National Key R&D Program of China (2018YFC1004901 and 2016YFC0905103), the Shanghai Sailing Program (18YF1424800), the Shanghai Municipal Commission of Science and Technology Program (15411964000) and the Shanghai 'Rising Stars of Medical Talent' Youth Development Program Clinical Laboratory Practitioners Program (201972). The authors declare no competing interests.

TRIAL REGISTRATION NUMBER

N/A.

ChromInst: A single cell sequencing technique to accomplish pre-implantation comprehensive chromosomal screening overnight

Next Generation Sequencing (NGS) is a powerful tool getting into the field of clinical examination. Its preliminary application in pre-implantation comprehensive chromosomal screening (PCCS) of assisted reproduction (test-tube baby) has shown encouraging outcomes that improves the success rate of in vitro fertilization. However, the conventional NGS library construction is time consuming. In addition with the whole genome amplification (WGA) procedure in prior, makes the single cell NGS assay hardly be accomplished within an adequately short turnover time in supporting fresh embryo implantation. In this work, we established a concise single cell sequencing protocol, ChromInst, in which the single cell WGA and NGS library construction were integrated into a two-step PCR procedure of ~ 2.5hours reaction time. We then validated the feasibility of ChromInst for overnight PCCS assay by examining 14 voluntary donated embryo biopsy samples in a single sequencing run of Miseq with merely 13M reads production. The good compatibility of ChromInst with the restriction of Illumina sequencing technique along with the good library yield uniformity resulted superior data usage efficiency and reads distribution evenness that ensures precisely distinguish of 6 normal embryos from 8 abnormal one with variable chromosomal aneuploidy. The superior succinctness and effectiveness of this protocol permits its utilization in other time limited single cell NGS applications.

Complex mosaic blastocysts after preimplantation genetic testing: prevalence and outcomes after re-biopsy and re-vitrification

RESEARCH QUESTION

What is the incidence of complex mosaic in preimplantation genetic testing (PGT) blastocysts and can it be managed in clinical practice?

DESIGN

A retrospective study of PGT cycles conducted between January 2018 and October 2019 at a single centre. Biopsies of blastocysts were collected and analysed by next-generation sequencing (NGS). Complex mosaic blastocysts were defined as those with three or more mosaic chromosomes. The cryopreserved complex mosaic blastocysts underwent a second round of biopsy, NGS analysis and vitrification. The euploid blastocysts identified by the re-biopsy were warmed again for embryo transfer. The main outcomes included the prevalence of the complex mosaic and the ongoing pregnancy rate.

RESULTS

The prevalence of the complex mosaic was 2.4% (437/17,979). The prevalence of the complex mosaic was not associated with maternal age and morphological quality. A total of 89 complex mosaic blastocysts underwent re-biopsy and 96.6% (86/89) survived the first warming. For the re-biopsy samples, 61.6% (53/86) were euploid. The poor-quality blastocysts had higher rates of aneuploidy compared with good-quality blastocysts. The survival rate for blastocysts undergoing the second warming was 100% (18/18) and resulted in an ongoing pregnancy rate of 38.9% (7/18) as well as the birth of six healthy infants.

CONCLUSION

Re-biopsy may rescue blastocysts with development potential for transfer and improve the cumulative pregnancy rate per stimulation cycle in patients containing complex mosaic blastocysts.

Next-Generation Sequencing-Based Pre-Implantation Genetic Testing for Aneuploidy (PGT-A): First Report from Saudi Arabia

Recently, high-throughput next-generation sequencing (NGS)-based preimplantation genetic testing for aneuploidies techniques came into use. This technique is essential for successful embryo transfer and accomplishing pregnancy, thus reducing the time and cost of additional cycles. In this study, we describe our first experience in introducing an NGS-based preimplantation genetic testing for aneuploidy (PGT-A) service using next-generation sequencing in King Abdulaziz Medical City located in Riyadh, Saudi Arabia. Our main goal was to report the successful implementation of this new technology in clinical practice and highlight the factors that may affect the results. In total, 200 blastomere biopsies were obtained from 36 in vitro fertilization (IVF) cycles from Saudi couples suffering from prolonged infertility or recurrent embryo transfer failure. NGS-based PGT-A was performed in all embryos. The results were analyzed in five age groups, showing that aneuploidy rates increased with maternal age. Moreover, the results also showed that complex abnormal embryos with (2-5) aneuploidy are the most common type of embryos. Additionally, our data showed that chromosome 16-related abnormality was the most frequent abnormality detected among all reported abnormalities. In conclusion, our study suggests that NGS-based PGT-A is an applicable and reliable technique for routine-based embryo screening, especially for couples suffering from recurrent miscarriages or multiple embryo transfer failures.

D-karyo-A New Prenatal Rapid Screening Test Detecting Submicroscopic CNVs and Mosaicism

Chromosomal microarray analysis (CMA), recently introduced following conventional cytogenetic technology, can detect submicroscopic copy-number variations (CNVs) in cases previously diagnosed as "cytogenetically benign". At present, rapid and accurate chromosomal analysis is required in prenatal diagnostics, but prenatal CMA is not widely used due to its high price and long turnaround time. We introduced a new prenatal screening method named digital karyotyping (D-karyo), which utilizes a preimplantation genetic test for the aneuploidy (PGT-A) platform. First, we conducted a preliminary experiment to compare the original PGT-A method to our modified method. Based on the preliminary results, we decided to implement the modified strategy without whole-genome amplification (WGA) and combined it with three analytical software packages. Next, we conducted a prospective study with 824 samples. According to the indication for invasive tests, the D-karyo positive rates were 2.5% and 5.0%, respectively, in the screening positive group with NT ≥ 3.5 mm and the group with fetal abnormalities by ultrasound. D-karyo is a breakthrough modality that can detect submicroscopic CNVs ≥ 1.0 Mb accurately in only 10.5 h for 24 samples at a low cost. Implementing D-karyo as a prenatal rapid screening test will reduce unnecessary CMA and achieve more accurate prenatal genetic testing than G-banding.

Third-generation sequencing: any future opportunities for PGT?

PURPOSE

To investigate use of the third-generation sequencing (TGS) Oxford Nanopore system as a new approach for preimplantation genetic testing (PGT).

METHODS

Embryos with known structural variations underwent multiple displacement amplification to create fragments of DNA (average ~ 5 kb) suitable for sequencing on a nanopore.

RESULTS

High-depth sequencing identified the deletion interval for the relatively large HBA1/2--SEA alpha thalassemia deletion. In addition, STRs were able to be identified in the primary sequence data for potential use in conventional PGT-M linkage confirmation. Sequencing of amplified embryo DNA carrying a translocation enabled balanced embryos to be identified and gave the precise identification of translocation breakpoints, offering the opportunity to differentiate carriers from non-carrier embryos. Low-pass sequencing gave reproducible profiles suitable for simple identification of whole-chromosome and segmental aneuploidies.

CONCLUSION

TGS on the Oxford Nanopore is a possible alternative and versatile approach to PGT with potential for performing economical workups where the long read sequencing information can be used for assisting in a traditional PGT workup to design an accurate and reliable test. Additionally, application of TGS has the possibility of providing combined PGT-A/SR or in selected stand-alone PGT-M cases involving pathogenic deletions. Both of these applications offer the opportunity for simultaneous aneuploidy detection to select either balanced embryos for transfer or additional carrier identification. The low cost of the instrument offers new laboratories economical entry into onsite PGT.

Evaluating in vitro fertilization outcomes of patients with low body mass index following frozen-thawed embryo transfer

OBJECTIVE

To determine the relationship between patients with a low body mass index (BMI; calculated as weight in kilograms divided by the square of height in meters) and in vitro fertilization (IVF) outcomes following frozen-thawed embryo transfer (FET).

METHODS

Retrospective cohort study including 12 618 women aged 20-46 years with an underweight (<18.5) or normal weight (18.5-24.9) BMI who underwent controlled ovarian stimulation for IVF in a private and academic IVF center between August 2002 and December 2019.

RESULTS

Anti-Müllerian hormone, peak estradiol levels, number of MII oocytes, and fertilized oocytes were greater in the underweight group compared with the normal weight group. The total required gonadotropin dose was lower in the underweight patients compared with the normal weight patients. MII, fertilization, blastulation, and euploid rates did not differ before and after adjusting for confounders between BMI groups. In a cohort of 316 patients who underwent preimplantation genetic testing for aneuploidy and single euploid FET, pregnancy loss, pregnancy, clinical pregnancy, and live birth rates before and after controlling for covariates were similar between groups.

CONCLUSION

Although there are known fetal growth or obstetrical issues associated in patients with a low BMI, it is reassuring that these risks do not extend to embryologic or clinical outcomes from IVF treatment.

Successful four-factor preimplantation genetic testing: α- and β-thalassemia, human leukocyte antigen typing, and aneuploidy screening

Our study established an effective next-generation sequencing (NGS) protocol for four-factor preimplantation genetic testing (PGT) using  α- and β-thalassemia, human leukocyte antigen (HLA) typing, and aneuploidy screening. Three couples, in whom both partners were α- and β-double thalassemia carriers, underwent PGT between 2016 and 2018. These individuals sought an opportunity for hematopoietic stem cell transplantation to save their children from β-thalassemia major. A total of 35 biopsied trophectoderm samples underwent multiple displacement amplification (MDA). PGT for α- and β-thalassemia and HLA typing were performed on MDA products using NGS-based single-nucleotide polymorphism (SNP) haplotyping. Although two samples failed MDA, 94.3% (33/35) of samples were successfully amplified, achieving conclusive PGT results. Furthermore, 51.5% (17/33) of the embryos were diagnosed as unaffected non-carriers or carriers. Of the 17 unaffected embryos, nine (52.9%) were tested further  and identified as euploid via NGS-based aneuploid screening, in which five had HLA types matching affected children. One family did not achieve any unaffected euploid embryos. The two other families transferred HLA-matched and unaffected euploid embryos, resulting in two healthy 'savior babies.' NGS-PGT results were confirmed in prenatal diagnosis. Therefore, NGS-SNP was effective in performing PGT for multipurpose detection within a single PGT cycle.

The Incidence of Mosaicism for Individual Chromosome in Human Blastocysts Is Correlated With Chromosome Length

Mosaicism, known as partial aneuploidies, mostly originates from mitotic errors during the post-zygotic stage; it consists of different cell lineages within a human embryo. The incidence of mosaicism has not been shown to correlate with maternal age, and its correlation with individual chromosome characteristics has not been well investigated. In this study, the results of preimplantation genetic testing for aneuploidy (PGT-A) derived from 4,036 blastocysts (930 IVF couples) were collected from 2015 to 2017. Via next-generation sequencing for comprehensive chromosome screening, embryo ploidy was identified as aneuploid, mosaic, and euploid. Total mosaicism was classified into two categories: "mosaic euploid/aneuploidy" (with mosaic aneuploidy between 20 and 80%) and "mosaic and aneuploidy" (a uniformly abnormal embryo superimposed with mosaic aneuploidies). Frequency of mosaicism was analyzed according to the function of chromosomal lengths, which divides involved chromosomes into three groups: group A (156-249 Mb), group B (102-145 Mb), and group C (51-90 Mb). The results show that the aneuploidy was more frequent in group C than in group A and group B (A: 23.7%, B: 35.1, 41.2%, p < 0.0001), while the mosaicism was more frequent in group A and group B than in group C [(Mosaic euploid/aneuploid) A: 14.6%, B: 12.4%, C: 9.9%, p < 0.0001; (mosaic and aneuploid) A: 21.3%, B: 22.9%, C: 18.9%, p < 0.0001; (Total mosaicism) A: 35.9%, B: 35.3%, C: 28.8%, p < 0.0001]. The significantly higher frequency of aneuploidy was on the shorter chromosome (< 90 Mb), and that of mosaicism was on the longer chromosomes (> 100 Mb). The length association did not reach significance in the patients with advanced age (≥ 36 years), and of the chromosome-specific mosaicism rate, the highest prevalence was on chromosome 14 (5.8%), 1 (5.7%), and 9 (5.6%). Although the length association was observed via group comparison, there may be affecting mechanisms other than chromosomes length. Eventually, twenty patients with mosaic embryo cryotransfers resulted in six live births. No significant correlation was observed between the transfer outcomes and chromosome length; however, the analysis was limited by small sample size.

Mitochondrial replacement by genome transfer in human oocytes: Efficacy, concerns, and legality

BACKGROUND

Pathogenic mitochondrial (mt)DNA mutations, which often cause life-threatening disorders, are maternally inherited via the cytoplasm of oocytes. Mitochondrial replacement therapy (MRT) is expected to prevent second-generation transmission of mtDNA mutations. However, MRT may affect the function of respiratory chain complexes comprised of both nuclear and mitochondrial proteins.

METHODS

Based on the literature and current regulatory guidelines (especially in Japan), we analyzed and reviewed the recent developments in human models of MRT.

MAIN FINDINGS

MRT does not compromise pre-implantation development or stem cell isolation. Mitochondrial function in stem cells after MRT is also normal. Although mtDNA carryover is usually less than 0.5%, even low levels of heteroplasmy can affect the stability of the mtDNA genotype, and directional or stochastic mtDNA drift occurs in a subset of stem cell lines (mtDNA genetic drift). MRT could prevent serious genetic disorders from being passed on to the offspring. However, it should be noted that this technique currently poses significant risks for use in embryos designed for implantation.

CONCLUSION

The maternal genome is fundamentally compatible with different mitochondrial genotypes, and vertical inheritance is not required for normal mitochondrial function. Unresolved questions regarding mtDNA genetic drift can be addressed by basic research using MRT.

EXT1 and EXT2 Variants in 22 Chinese Families With Multiple Osteochondromas: Seven New Variants and Potentiation of Preimplantation Genetic Testing and Prenatal Diagnosis

Multiple osteochondromas (MO), the most common type of benign bone tumor, is an autosomal dominant skeletal disorder characterized by multiple cartilage-capped bony protuberances. In most cases, EXT1 and EXT2, which encode glycosyltransferases involved in the biosynthesis of heparan sulfate, are the genes responsible. Here we describe the clinical, phenotypic and genetic characterization of MO in 22 unrelated Chinese families involving a total of 60 patients. Variant detection was performed by means of a battery of different techniques including Sanger sequencing and whole-exome sequencing (WES). The pathogenicity of the missense and splicing variants was explored by means of in silico prediction algorithms. Sixteen unique pathogenic variants, including 10 in the EXT1 gene and 6 in the EXT2 gene, were identified in 18 (82%) of the 22 families. Fourteen (88%) of the 16 variants were predicted to give rise to truncated proteins whereas the remaining two were missense. Seven variants were newly described here, further expanding the spectrum of MO-causing variants in the EXT1 and EXT2 genes. More importantly, the identification of causative variants allowed us to provide genetic counseling to 8 MO patients in terms either of preimplantation genetic testing (PGT) or prenatal diagnosis, thereby preventing the reoccurrence of MO in the corresponding families. This study is the first to report the successful implementation of PGT in MO families and describes the largest number of subjects undergoing prenatal diagnosis to date.

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

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

Higher chromosomal abnormality rate in blastocysts from young patients with idiopathic recurrent pregnancy loss

OBJECTIVE

To determine whether the incidence of chromosomal abnormalities in blastocysts is higher in patients with idiopathic recurrent pregnancy loss (iRPL) who underwent preimplantation genetic testing for aneuploidy (PGT-A) than in those who underwent preimplantation genetic testing for monogenic defects (PGT-M).

DESIGN

Retrospective cohort study.

SETTING

University-affiliated reproductive center.

PATIENT(S)

A total of 62 patients with iRPL underwent 101 PGT-A cycles (iRPL group), and 212 patients underwent 311 PGT-M cycles (control group).

INTERVENTIONS(S)

Blastocyst biopsy and comprehensive chromosome screening technologies, including single-nucleotide polymorphism microarrays and next-generation sequencing.

MAIN OUTCOME MEASURE(S)

Incidence of chromosomal abnormalities in blastocysts and clinical miscarriage (CM) rate.

RESULT(S)

Stratification analysis by maternal age showed an increased incidence of chromosomal abnormalities in the iRPL group aged ≤35 years (48.9% vs. 36.9%), whereas no significant increase was found in the iRPL group aged >35 years (66.9% vs. 61.4%). After transfer of euploid embryos, women aged ≤35 years with iRPL exhibited an increased CM rate compared with the control group (26.1% vs. 3.1%).

CONCLUSION(S)

Young patients with iRPL have a significantly higher rate of chromosomal abnormalities in blastocysts compared with patients with no or sporadic CM. Although euploid embryos were transferred after PGT-A, young patients with iRPL had a higher CM rate, which may indicate that chromosomal abnormalities might not be the only causal factor for iRPL. Therefore, the role of PGT-A in iRPL still needs to be clarified.

Necessity is the mother of invention and the evolutionary force driving the success of in vitro fertilization

During the last few decades, millions of healthy children have been born with the aid of in vitro fertilization (IVF). This success belies the fact that IVF treatment is comprised of a complex series of interventions starting with a customized control ovarian stimulation protocol. This is followed by the induction of oocyte maturation, the retrieval of mature oocytes and in vitro fertilization, which often involves the microinjection of a single sperm into the oocyte. After fertilization, the resulting embryos are cultured for up to 7 days. The best embryos are transferred into the uterus where the embryo implants and hopefully develops into a healthy child. However, frequently the best embryos are biopsied and frozen. The biopsied cells are analyzed to identify those embryos without chromosomal abnormalities. These embryos are eventually thawed and transferred with pregnancy rates as good if not better than embryos that are not biopsied and transferred in a fresh cycle. Thus, IVF treatment requires the coordinated efforts of physicians, nurses, molecular biologists and embryologists to conduct each of these multifaceted phases in a seamless and flawless manner. Even though complex, IVF treatment may seem routine today, but it was not always the case. In this review the evolution of human IVF is presented as a series of innovations that resolved a technical hurdle in one component of IVF while creating challenges that eventually lead to the next major advancement. This step-by-step evolution in the treatment of human infertility is recounted in this review.

What is the reproductive potential of day 7 euploid embryos?

STUDY QUESTION

What is the rate of euploidy and the reproductive potential of embryos biopsied after 6 days of development?

SUMMARY ANSWER

Embryos biopsied after 6 days of development have higher rates of aneuploidy; however, day 7 euploid embryos selected at transfer can achieve acceptable pregnancy rates and live birth (LB) outcomes.

WHAT IS KNOWN ALREADY

Recent publications have shown promising treatment results after euploid day 7 embryo transfers (ETs), albeit these studies were limited by small sample sizes. Whereas the current clinical standard has been to discard embryos that do not reach expansion by day 6 of development, the lack of robust data surrounding the clinical utility of day 7 embryos warrants further evaluation.

STUDY DESIGN, SIZE, DURATION

Retrospective cohort analysis in a single, academic in vitro fertilization (IVF) center from January 2012 to March 2018. A total of 25 775 embryos underwent trophectoderm (TE) biopsy and preimplantation genetic testing for aneuploidy (PGT-A). Additionally, the clinical IVF outcomes of 3824 single, euploid frozen embryo transfer (FET) cycles were evaluated.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Cohorts were segregated by day of TE biopsy following oocyte retrieval (day 5, day 6 or day 7). PGT-A was performed to identify embryonic ploidy rates. Secondly, IVF and LB outcomes after single, euploid FET were evaluated for each cohort.

MAIN RESULTS AND THE ROLE OF CHANCE

A total of day 5 (n = 12 535), day 6 (n = 11 939) and day 7 (n = 1298) embryos were included in the study analysis. The rate of embryo euploidy was significantly lower in day 7 blastocysts compared to day 5 or day 6 cohorts (day 7 = 40.5%; day 5 = 54.7%; day 6 = 52.9%; (P < 0.0001)). After adjusting for age, anti-Müllerian hormone, BMI, embryo quality and number of embryos biopsied, there was a significant association between aneuploidy and embryos biopsied on day 7 when compared to day 5 biopsied embryos (OR = 1.34, CI 95% 1.09-1.45, P = 0.001) and day 6 biopsied embryos (OR = 1.26, CI95% 1.07-1.16, P < 0.001).A sub-analysis of subsequent 3824 single, euploid FET cycles (day 5: n = 2321 cycles; day 6: n = 1381 cycles; and day 7: n = 116 cycles) showed significant differences among cohorts in implantation, clinical pregnancy, LB and clinical loss rates. There was a significant decrease in the odds of implantation, clinical pregnancy and LB, but no association with clinical loss or multiple pregnancy rates in patients who utilized day 7-biopsied embryos during treatment.

LIMITATIONS, REASONS FOR CAUTION

The retrospective nature of the study and potential variability in the study center's laboratory protocol(s) compared to other reproductive treatment centers may limit the external validity of our findings. Additionally, patients who transferred euploid embryos, biopsied on day 7 of development due to an absence of day 5 or day 6 counterparts, may have introduced selection bias in this study.

WIDER IMPLICATIONS OF THE FINDINGS

Embryonic developmental stage, morphological grade and ploidy status are paramount factors affecting ET selection and implantation potential. This study reveals that embryos ineligible for TE biopsy on day 5 or day 6 of development may benefit from extended culture to day 7. Our study demonstrates patient benefit when extended culture to day 7 of development is routinely performed for embryos failing to meet biopsy criteria by day 5 or 6.

STUDY FUNDING/COMPETING INTEREST(S)

No funding was received for the realization of this manuscript. Dr Alan Copperman is Advisor or Board Member of Sema 4 (Stake holder in Data), Progyny and Celmatix.

TRIAL REGISTRATION NUMBER

This retrospective analysis was approved by an Institutional Review Board (WIRB PRO NUM: 20161791; Study Number: 1167398).

Clinical application of embryo aneuploidy testing by next-generation sequencing

We review here the evolution in the field of embryo aneuploidy testing over the last 20 years, from the analysis of a subset of chromosomes by fluorescence in situ hybridisation to the transition toward a more comprehensive analysis of all 24 chromosomes. This current comprehensive aneuploidy testing most commonly employs next-generation sequencing (NGS). We present our experience in over 130 000 embryo biopsies using this technology. The incidence of aneuploidy was lower in trophectoderm biopsies compared to cleavage-stage biopsies. We also confirmed by NGS that embryo aneuploidy rates increased with increasing maternal age, mostly attributable to an increase in complex aneuploid embryos. In contrast, the number of MII oocytes retrieved or the use of oocyte vitrification did not affect aneuploidy rates. Similarly, neither maternal age, oocyte number, nor oocyte vitrification affected the incidence of mosaicism. Analysis of clinical outcomes, indications, and potential benefits of embryo aneuploidy testing revealed advanced maternal age as the most favored group, with some evidence of improved delivery rate per transfer as well as decreased miscarriage rates and time to pregnancy. Other indications are: recurrent miscarriage, repetitive implantation failure, severe male factor, previous trisomic pregnancy, and good prognosis patients mainly undergoing single embryo transfer, with the latter indication used to reduce the occurrence of multiple pregnancies without compromising cycle outcome. In conclusion, NGS has become the most appropriate technology for aneuploidy testing in trophectoderm biopsies, with accurate results, high throughput, and cost efficiency. This technology can be also applied to the analysis of the embryonic cell free DNA released to the culture media at blastocyst stage. This is a promising approach towards a non-invasive preimplantation genetic testing of aneuploidy.

Coenzyme Q10 supplementation of human oocyte in vitro maturation reduces postmeiotic aneuploidies

OBJECTIVE

To evaluate the effect of coenzyme Q10 (CoQ10) supplementation on oocyte maturation rates and postmeiotic aneuploidy rates during in vitro maturation (IVM) of human oocytes.

DESIGN

Clinical laboratory observation.

SETTING

Hospital and university laboratories.

PATIENT(S)

Forty-five patients aged ≥38 years and 18 patients aged ≤30 years undergoing in vitro fertilization.

INTERVENTION(S)

The germinal vesicle-stage oocytes and associated cumulus cells were cultured in IVM media for 24-48 hours with or without 50 μmol/L CoQ10. Oocyte maturation rates were determined based on the presence or absence of the first polar body. Postmeiotic aneuploidies were determined using next-generation sequencing analyses of biopsied polar bodies.

MAIN OUTCOME MEASURE(S)

Oocyte maturation rates, postmeiotic oocyte aneuploidy rates, and chromosome aneuploidy frequencies.

RESULT(S)

In women aged 38-46 years, 50 μmol/L CoQ10 significantly increased oocyte maturation rates (82.6% vs. 63.0%; P=.035), reduced oocyte aneuploidy rates (36.8% vs. 65.5%; P=.020), and reduced chromosome aneuploidy frequencies (4.1% vs. 7.0%; P=.012. In women aged ≤30 years, we failed to demonstrate an effect of CoQ10 on oocyte maturation rates or postmeiotic aneuploidies.

CONCLUSION(S)

CoQ10 supplementation during IVM increased oocyte maturation rates and reduced postmeiotic aneuploidies for older women.

Improved clinical outcomes of preimplantation genetic testing for aneuploidy using MALBAC-NGS compared with MDA-SNP array

BACKGROUND

To assess whether preimplantation genetic testing for aneuploidy with next generation sequencing (NGS) outweighs single nucleotide polymorphism (SNP) array in improving clinical outcomes.

METHODS

A retrospective analysis of the clinical outcomes of patients who underwent PGT-A treatment in a single center from January 2013 to December 2017.A total of 1418 couples who underwent PGT-A treatment were enrolled, of which 805 couples used NGS for PGT-A, while the remaining 613 couples used SNP array for PGT-A. Clinical pregnancy rate, miscarriage rate and healthy baby rate were compared between the MALBAC-NGS-PGT-A and MDA-SNP-PGT-A groups.

RESULTS

After testing karyotypes of 5771 biopsied blastocysts, 32.2% (1861/5771) were identified as chromosomally normal, while 67.8% were chromosomally abnormal. In terms of clinical outcomes, women in the MALBAC-NGS-PGT-A group had a significantly higher clinical pregnancy rate (50.5% vs 41.7%, p = 0.002) and healthy baby rate (39.6% vs 31.4%, p = 0.003), and a lower miscarriage rate (15.5% vs 22.8%, p = 0.036).

CONCLUSION

This is the largest study reporting the extensive application of NGS-based PGT-A, whilst comparing the clinical outcomes of MALBAC-NGS-PGT-A and MDA-SNP-PGT-A. The results provide greater evidence supporting the wider use of NGS in PGT-A, not only for its lower cost but also for its improved clinical outcomes compared to SNP-based PGT-A.

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.

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.

THE REPORTED SUCCESSFUL BABY DELIVERY AFTER PREIMPLANTATION GENETIC TESTING FOR ANEUPLOIDIES (PGT-A) BY MEANS OF NEXT GENERATION SEQUENCING (NGS)

The aim of this case report is to demonstrate a successful delivery of a baby after transfer of a blastocyst tested for aneuplodies by means of NGS. A woman aged 35 having two miscarriages decided for ICSI program with PGT-A analysis. Six eggs were fertilized out of 9 metaphase II oocytes. Five good quality blastocysts were submitted for genetic screening using 24-chromosome next generation sequencing (NGS). Two blastocysts were diagnosed as euploid and recommended for transfer. One euploid blastocyst was thawed and transferred to the patient’s uterus lining. Successful pregnancy was confirmed at 7 weeks of gestation with heartbeat. Successful delivery was achieved by Caesarean section at 38-39 weeks of gestation. Karyotyping demonstrated healthy genetic constitution of a baby. This case demonstrates a good evidence and potential of a transport scheme collaboration between IVF and genetic laboratories.

Preimplantation Genetic Testing: Where We Are Today

BACKGROUND

Preimplantation genetic testing (PGT) is widely used today in in-vitro fertilization (IVF) centers over the world for selecting euploid embryos for transfer and to improve clinical outcomes in terms of embryo implantation, clinical pregnancy, and live birth rates.

METHODS

We report the current knowledge concerning these procedures and the results from different clinical indications in which PGT is commonly applied.

RESULTS

This paper illustrates different molecular techniques used for this purpose and the clinical significance of the different oocyte and embryo stage (polar bodies, cleavage embryo, and blastocyst) at which it is possible to perform sampling biopsies for PGT. Finally, genetic origin and clinical significance of embryo mosaicism are illustrated.

CONCLUSIONS

The preimplantation genetic testing is a valid technique to evaluated embryo euploidy and mosaicism before transfer.

Preimplantation Genetic Testing for Chromosomal Abnormalities: Aneuploidy, Mosaicism, and Structural Rearrangements

There is a high incidence of chromosomal abnormalities in early human embryos, whether they are generated by natural conception or by assisted reproductive technologies (ART). Cells with chromosomal copy number deviations or chromosome structural rearrangements can compromise the viability of embryos; much of the naturally low human fecundity as well as low success rates of ART can be ascribed to these cytogenetic defects. Chromosomal anomalies are also responsible for a large proportion of miscarriages and congenital disorders. There is therefore tremendous value in methods that identify embryos containing chromosomal abnormalities before intrauterine transfer to a patient being treated for infertility—the goal being the exclusion of affected embryos in order to improve clinical outcomes. This is the rationale behind preimplantation genetic testing for aneuploidy (PGT-A) and structural rearrangements (-SR). Contemporary methods are capable of much more than detecting whole chromosome abnormalities (e.g., monosomy/trisomy). Technical enhancements and increased resolution and sensitivity permit the identification of chromosomal mosaicism (embryos containing a mix of normal and abnormal cells), as well as the detection of sub-chromosomal abnormalities such as segmental deletions and duplications. Earlier approaches to screening for chromosomal abnormalities yielded a binary result of normal versus abnormal, but the new refinements in the system call for new categories, each with specific clinical outcomes and nuances for clinical management. This review intends to give an overview of PGT-A and -SR, emphasizing recent advances and areas of active development.

Time of morulation and trophectoderm quality are predictors of a live birth after euploid blastocyst transfer: a multicenter study

OBJECTIVE

To investigate whether the morphodynamic characterization of a euploid blastocyst's development allows a higher prediction of a live birth after single-embryo-transfer (SET).

DESIGN

Observational cohort study conducted in two phases: training and validation.

SETTING

Private in vitro fertilization centers.

PATIENT(S)

Euploid blastocysts: 511 and 319 first vitrified-warmed SETs from 868 and 546 patients undergoing preimplantation genetic testing for aneuploidies (PGT-A) in the training and validation phase, respectively.

INTERVENTION(S)

Data collected from time of polar body extrusion to time of starting blastulation, and trophectoderm and inner-cell-mass static morphology in all embryos cultured in a specific time-lapse incubator with a continuous medium. Logistic regressions conducted to outline the variables showing a statistically significant association with live birth. In the validation phase, these variables were tested in an independent data set.

MAIN OUTCOME MEASURE(S)

Live births per SET.

RESULT(S)

The average live birth rate (LBR) in the training set was 40% (N = 207/511). Only time of morulation (tM) and trophectoderm quality were outlined as putative predictors of live birth at two IVF centers. In the validation set, the euploid blastocysts characterized by tM <80 hours and high-quality trophectoderm resulted in a LBR of 55.2% (n = 37/67), while those with tM ≥ 80 hours and a low-quality trophectoderm resulted in a LBR of 25.5% (N = 13/51).

CONCLUSION(S)

Time of morulation and trophectoderm quality are better predictors of a euploid blastocyst's reproductive competence. Our evidence was reproducible across different centers under specific culture conditions. These data support the crucial role of morulation for embryo development, a stage that involves massive morphologic, cellular, and molecular changes and deserves more investigation.

Concordance of various chromosomal errors among different parts of the embryo and the value of re-biopsy in embryos with segmental aneuploidies

Chromosomal mosaicism detected during preimplantation genetic testing for aneuploidy (PGT-A) and its impact on embryo implantation have been widely discussed, and healthy live births from mosaic embryos were reported by many groups. On the other hand, only very few studies have focused on segmental chromosome aneuploidies and their clinical impact. Eighty-nine embryos with various PGT-A results (trophectoderm 1: TE1) were re-analysed using a second trophectoderm biopsy (TE2) and the rest of the embryo (RE) for testing. Of 19 euploid TE1 biopsies, 18 were concordant across TE2 and RE. Similarly, whole chromosomal aneuploidies were concordant in 59 of 62 TE1-TE2 and 58 TE1-RE. In contrast, from 31 segmental aneuploidies detected in TE1, only 15 were observed again in TE2 and 14 in RE. If a TE1 segmental abnormality appeared again in TE2, it was almost always present in RE (17/18) as well. Moreover, when a TE1 segmental abnormality was not detected in TE2, in 12 out of 13 cases RE was also unaffected. Similarly, only 1 of 26 TE1 whole chromosome mosaics were repeated in TE2 and 7 in RE. Our study confirms that euploid and whole chromosomal aneuploidy results are highly predictive of the embryo. In contrast, mosaicism has a very low concordance rate. Most importantly, re-biopsy of embryos with segmental aneuploidies demonstrated that they are mostly not uniform across the embryo. Finally, in the case of segmental aneuploidy, the second biopsy enables an accurate prediction of the real status of the embryo and could be offered to patients undergoing PGT-A.