A prospective study of non-invasive preimplantation genetic testing for aneuploidies (NiPGT-A) using next-generation sequencing (NGS) on spent culture media (SCM)

Effects of first and second division modes on euploidy acquisition in human embryo

The aim of this study was to non-invasively investigate euploid embryos using methods other than pre-implantation genetic testing for aneuploidy. The study focused on direct cleavage (DC) observed during early embryo development. We also investigated the relationship between the mode of early embryo division and embryo ploidy. Embryos were divided into the normal cleavage (NC) and DC groups, and the DC group was further subdivided into the DC-First (DC-F) and DC-Second (DC-S) groups, depending on whether DC was observed at the first or second cleavage, respectively. The acquisition rates of euploid embryos and embryos appropriate for transfer were compared between the groups. Our results revealed that the timing of the first division did not differ between blastocyst grades or in embryos with varying degrees of ploidy. Further, the timing of the first cleavage did not affect the acquisition rate of embryos appropriate for transfer and euploid embryo formation rate did not significantly differ between the DC and NC groups. We also noted that for embryos appropriate for transfer, euploidy acquisition rate did not differ significantly between the DC and NC groups. Further, the euploidy acquisition rate of embryos did not differ between the DC-F and DC-S groups. However, the acquisition rate of embryos appropriate for transfer, including those with low mosaicism, was significantly higher in the DC-S group than in the DC-F group. These findings indicated that the number of good-quality blastocysts formed was significantly higher in the NC group than in the DC group and the acquisition rate of embryos appropriate for transfer, including those with low mosaicism, was significantly higher in the DC-S group than in the DC-F group.

A novel non-invasive embryo evaluation method (NICS-Timelapse) with enhanced predictive precision and clinical impact

The selection of the finest possible embryo in in-vitro fertilization (IVF) was crucial and revolutionary, particularly when just one embryo is transplanted to lessen the possibility of multiple pregnancies. However, practical usefulness of currently used methodologies may be constrained. Here, we established a novel non-invasive embryo evaluation method that combines non-invasive chromosomal screening (NICS) and Timelapse system along with artificial intelligence algorithms. With an area under the curve (AUC) of 0.94 and an accuracy of 0.88, the NICS-Timelapse model was able to predict blastocyst euploidy. The performance of the model was further evaluated using 75 patients in various clinical settings. The clinical pregnancy and live birth rates of embryos predicted by the NICS-Timelapse model, showing that embryos with higher euploid probabilities were associated with higher clinical pregnancy and live birth rates. These results demonstrated the NICS-Timelapse model's significantly wider application in clinical IVF due to its excellent accuracy and noninvasiveness.

Culture time to optimize embryo cell-free DNA analysis for frozen-thawed blastocysts undergoing noninvasive preimplantation genetic testing for aneuploidy

OBJECTIVE

To investigate the ideal time in culture to optimize embryo cell-free deoxyribonucleic acid (cfDNA) analysis in frozen-thawed blastocysts undergoing noninvasive preimplantation genetic testing for aneuploidy (PGT-A). Cell-free DNA is released into the spent blastocyst media (spent media) by the embryo. However, the optimal timing to determine maximal cfDNA in the case of frozen-thawed blastocysts undergoing noninvasive PGT-A remains to be elucidated.

DESIGN

In this prospective observational study, 135 spent media and corresponding whole blastocysts were collected from January 2021 through March 2022.

SETTING

Private fertility clinics.

PATIENTS

Day-5 frozen-thawed blastocysts were cultured for 8 hours (Day-5 Short) or 24 hours (Day-5 Long), whereas day-6 frozen-thawed blastocysts were cultured for 8 hours (Day-6 Short). The spent media and whole blastocysts were then collected for further analysis. Spent media and whole blastocysts were amplified using whole genome amplification and sequenced using next-generation sequencing.

MAIN OUTCOME MEASURES

Informativity and concordance rates between cfDNA in spent media and whole blastocyst DNA were compared according to the different times in culture.

RESULTS

When comparing time in culture, informativity rates for spent media were significantly higher for Day-5 Long and Day-6 Short (>91%) compared with the Day-5 Short group (<60%). A similar trend was observed for cases with and without a previous PGT-A. Regarding blastocyst expansion grade, informativity rates were lower on Day-5 Short compared with Day-5 Long and Day-6 Short, regardless of expansion degree. This decrease was significant for Gardner-grade expansion grades 3, 4, and 5-6. In addition, for a similar time in culture, the grade of expansion did not have an impact on the informativity rates. For concordance rates, no significant differences were observed among the 3 groups. In all cases, concordance rates were 90.5% for Day-5 Short, 93.6% for Day-5 Long, and 92.3% for Day-6 Short. No impact of the expansion grade was observed on concordance rates.

CONCLUSION

Noninvasive PGT-A in frozen-thawed blastocysts yields very high concordance rates with whole blastocysts, possibly limiting the need for invasive PGT-A and making it available for a wider range of patients.

Evolution of Minimally Invasive and Non-Invasive Preimplantation Genetic Testing: An Overview

Preimplantation genetic testing (PGT) has become a common supplementary diagnοstic/testing tοol for in vitro fertilization (ΙVF) cycles due to a significant increase in cases of PGT fοr mοnogenic cοnditions (ΡGT-M) and de novο aneuplοidies (ΡGT-A) over the last ten years. This tendency is mostly attributable to the advancement and application of novel cytogenetic and molecular techniques in clinical practice that are capable of providing an efficient evaluation of the embryonic chromosomal complement and leading to better IVF/ICSI results. Although PGT is widely used, it requires invasive biopsy of the blastocyst, which may harm the embryo. Non-invasive approaches, like cell-free DNA (cfDNA) testing, have lower risks but have drawbacks in consistency and sensitivity. This review discusses new developments and opportunities in the field of preimplantation genetic testing, enhancing the overall effectiveness and accessibility of preimplantation testing in the framework of developments in genomic sequencing, bioinformatics, and the integration of artificial intelligence in the interpretation of genetic data.

When the Embryo Meets the Endometrium: Identifying the Features Required for Successful Embryo Implantation

Evaluation of the optimal number of embryos, their quality, and the precise timing for transfer are critical determinants in reproductive success, although still remaining one of the main challenges in assisted reproduction technologies (ART). Indeed, the success of in vitro fertilization (IVF) treatments relies on a multitude of events and factors involving both the endometrium and the embryo. Despite concerted efforts on both fronts, the overall success rates of IVF techniques continue to range between 25% and 30%. The role of the endometrium in implantation has been recently recognized, leading to the hypothesis that both the "soil" and the "seed" play a central role in a successful pregnancy. In this respect, identification of the molecular signature of endometrial receptivity together with the selection of the best embryo for transfer become crucial in ART. Currently, efforts have been made to develop accurate, predictive, and personalized tests to identify the window of implantation and the best quality embryo. However, the value of these tests is still debated, as conflicting results are reported in the literature. The purpose of this review is to summarize and critically report the available criteria to optimize the success of embryo transfer and to better understand current limitations and potential areas for improvement.

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

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

The Comparison of Two Whole-Genome Amplification Approaches for Noninvasive Preimplantation Genetic Testing (ni-PGT) and the Application Scenario of ni-PGT during the Fresh Cycle

Recently, noninvasive preimplantation genetic testing (ni-PGT) using degenerate oligonucleotide primer PCR (DOP-PCR) and multiple annealing and looping-based amplification cycle (MALBAC)-based whole-genome amplification (WGA) methods has demonstrated predictable results in embryo testing. However, a considerable heterogeneity of results has been reported in numerous studies on these two WGA methods. Our aim was to evaluate the current WGA method for ni-PGT while further clarifying the applicable scenarios of ni-PGT in the fresh cycle. A total of 173 embryos were tested with trophectoderm biopsy and ni-PGT. In the whole preimplantation genetic testing, the clinical concordance rates of the detection results of DOP-PCR and MALBAC with the corresponding trophectoderm biopsy results were 64.12% (84/131) and 68.99% (89/129), respectively (P = 0.405). However, in the detection of abnormal embryos, the detection efficiency of ni-PGT is significantly improved [MALBAC: 96.55% versus 68.99% (P < 0.001); and DOP-PCR: 89.09% versus 64.12% (P < 0.001)]. In addition, the diagnostic efficiency of ni-PGT in low-quality blastocysts was significantly higher than that in high-quality blastocysts [MALBAC: 95.24% versus 51.85% (P = 0.001); and DOP-PCR: 91.30% versus 48.15% (P = 0.001)]. These results contribute to further understanding ni-PGT and to clarifying its application scenario in the fresh cycle.

Systematic review and meta-analysis: does pre-implantation genetic testing for aneuploidy at the blastocyst stage improve live birth rate?

PURPOSE

To establish if preimplantation genetic testing for aneuploidy (PGT-A) at the blastocyst stage improves the composite outcome of live birth rate and ongoing pregnancy rate per embryo transfer compared to conventional morphological assessment.

METHODS

A systematic literature search was conducted using PubMed, EMBASE and Cochrane database from 1st March 2000 until 1st March 2022. Studies comparing reproductive outcomes following in vitro fertilisation using comprehensive chromosome screening (CCS) at the blastocyst stage with traditional morphological methods were evaluated.

RESULTS

Of the 1307 citations identified, six randomised control trials (RCTs) and ten cohort studies fulfilled the inclusion criteria. The pooled data identified a benefit between PGT-A and control groups in the composite outcome of live birth rate and ongoing pregnancy per embryo transfer in both the RCT (RR 1.09, 95% CI 1.02-1.16) and cohort studies (RR 1.50, 95% CI 1.28-1.76). Euploid embryos identified by CCS were more likely to be successfully implanted amongst the RCT (RR 1.20, 95% CI 1.10-1.31) and cohort (RR 1.69, 95% CI 1.29-2.21) studies. The rate of miscarriage per clinical pregnancy is also significantly lower when CCS is implemented (RCT: RR 0.73, 95% CI 0.56-0.96 and cohort: RR 0.48, 95% CI 0.32-0.72).

CONCLUSIONS

CCS-based PGT-A at the blastocyst biopsy stage increases the composite outcome of live births and ongoing pregnancies per embryo transfer and reduces the rate of miscarriage compared to morphological assessment alone. In view of the limited number of studies included and the variation in methodology between studies, future reviews and analyses are required to confirm these findings.

Update on preimplantation genetic testing for aneuploidy and outcomes of embryos with mosaic results

Preimplantation genetic testing for aneuploidy (PGT-A) is used as a frequent add-on for in-vitro fertilization (IVF) to improve clinical outcomes. The purpose is to select a euploid embryo following chromosomal testing on embryo biopsies. The current practice includes comprehensive chromosome screening (CCS) technology applied on trophectoderm (TE) biopsies. Despite its widespread use, PGT-A remains a controversial topic mainly because all of the RCTs comprised only good prognosis patients with 2 or more blastocysts available; hence the results are not generalizable to all groups of patients. Furthermore, with the introduction of the highly-sensitive platforms into clinical practice (i.e. next-generation sequencing [NGS]), a result consistent with intermediate copy number surfaced and is termed "Mosaic," consistent with a mixture of euploid and aneuploid cells within the biopsy sample. The optimal disposition and management of embryos with mosaic results is still an open question, as many 'mosaics' generated healthy live births with no identifiable congenital anomalies. The present article provides a complete and comprehensive up-to-date review on PGT-A. It discusses in detail the findings of all the published RCTs on PGT-A with CCS, comments on the subject of "mosaicism" and its current management, and describes the latest technique of non-invasive PGT-A.

Opening the black box: why do euploid blastocysts fail to implant? A systematic review and meta-analysis

BACKGROUND

A normal chromosomal constitution defined through PGT-A assessing all chromosomes on trophectoderm (TE) biopsies represents the strongest predictor of embryo implantation. Yet, its positive predictive value is not higher than 50-60%. This gap of knowledge on the causes of euploid blastocysts' reproductive failure is known as 'the black box of implantation'.

OBJECTIVE AND RATIONALE

Several embryonic, maternal, paternal, clinical, and IVF laboratory features were scrutinized for their putative association with reproductive success or implantation failure of euploid blastocysts.

SEARCH METHODS

A systematic bibliographical search was conducted without temporal limits up to August 2021. The keywords were '(blastocyst OR day5 embryo OR day6 embryo OR day7 embryo) AND (euploid OR chromosomally normal OR preimplantation genetic testing) AND (implantation OR implantation failure OR miscarriage OR abortion OR live birth OR biochemical pregnancy OR recurrent implantation failure)'. Overall, 1608 items were identified and screened. We included all prospective or retrospective clinical studies and randomized-controlled-trials (RCTs) that assessed any feature associated with live-birth rates (LBR) and/or miscarriage rates (MR) among non-mosaic euploid blastocyst transfer after TE biopsy and PGT-A. In total, 41 reviews and 372 papers were selected, clustered according to a common focus, and thoroughly reviewed. The PRISMA guideline was followed, the PICO model was adopted, and ROBINS-I and ROB 2.0 scoring were used to assess putative bias. Bias across studies regarding the LBR was also assessed using visual inspection of funnel plots and the trim and fill method. Categorical data were combined with a pooled-OR. The random-effect model was used to conduct the meta-analysis. Between-study heterogeneity was addressed using I2. Whenever not suitable for the meta-analysis, the included studies were simply described for their results. The study protocol was registered at http://www.crd.york.ac.uk/PROSPERO/ (registration number CRD42021275329).

OUTCOMES

We included 372 original papers (335 retrospective studies, 30 prospective studies and 7 RCTs) and 41 reviews. However, most of the studies were retrospective, or characterized by small sample sizes, thus prone to bias, which reduces the quality of the evidence to low or very low. Reduced inner cell mass (7 studies, OR: 0.37, 95% CI: 0.27-0.52, I2 = 53%), or TE quality (9 studies, OR: 0.53, 95% CI: 0.43-0.67, I2 = 70%), overall blastocyst quality worse than Gardner's BB-grade (8 studies, OR: 0.40, 95% CI: 0.24-0.67, I2 = 83%), developmental delay (18 studies, OR: 0.56, 95% CI: 0.49-0.63, I2 = 47%), and (by qualitative analysis) some morphodynamic abnormalities pinpointed through time-lapse microscopy (abnormal cleavage patterns, spontaneous blastocyst collapse, longer time of morula formation I, time of blastulation (tB), and duration of blastulation) were all associated with poorer reproductive outcomes. Slightly lower LBR, even in the context of PGT-A, was reported among women ≥38 years (7 studies, OR: 0.87, 95% CI: 0.75-1.00, I2 = 31%), while obesity was associated with both lower LBR (2 studies, OR: 0.66, 95% CI: 0.55-0.79, I2 = 0%) and higher MR (2 studies, OR: 1.8, 95% CI: 1.08-2.99, I2 = 52%). The experience of previous repeated implantation failures (RIF) was also associated with lower LBR (3 studies, OR: 0.72, 95% CI: 0.55-0.93, I2 = 0%). By qualitative analysis, among hormonal assessments, only abnormal progesterone levels prior to transfer were associated with LBR and MR after PGT-A. Among the clinical protocols used, vitrified-warmed embryo transfer was more effective than fresh transfer (2 studies, OR: 1.56, 95% CI: 1.05-2.33, I2 = 23%) after PGT-A. Lastly, multiple vitrification-warming cycles (2 studies, OR: 0.41, 95% CI: 0.22-0.77, I2 = 50%) or (by qualitative analysis) a high number of cells biopsied may slightly reduce the LBR, while simultaneous zona-pellucida opening and TE biopsy allowed better results than the Day 3 hatching-based protocol (3 studies, OR: 1.41, 95% CI: 1.18-1.69, I2 = 0%).

WIDER IMPLICATIONS

Embryo selection aims at shortening the time-to-pregnancy, while minimizing the reproductive risks. Knowing which features are associated with the reproductive competence of euploid blastocysts is therefore critical to define, implement, and validate safer and more efficient clinical workflows. Future research should be directed towards: (i) systematic investigations of the mechanisms involved in reproductive aging beyond de novo chromosomal abnormalities, and how lifestyle and nutrition may accelerate or exacerbate their consequences; (ii) improved evaluation of the uterine and blastocyst-endometrial dialogue, both of which represent black boxes themselves; (iii) standardization/automation of embryo assessment and IVF protocols; (iv) additional invasive or preferably non-invasive tools for embryo selection. Only by filling these gaps we may finally crack the riddle behind 'the black box of implantation'.

Evaluation of non-invasive gene detection in preimplantation embryos: a systematic review and meta-analysis

BACKGROUND

Genetic abnormalities in embryos are responsible for most miscarriages and repeated embryo implantation failures, so a reliable preimplantation genetic screening method is urgently needed. Non-invasive preimplantation genetic testing (niPGT) is a potential method for embryo genetic diagnosis. However, the value of its application is controversial. This meta-analysis aimed to investigate and validate the diagnostic value of niPGT in patients undergoing in vitro fertilization (IVF).

METHODS

This review used the "Preferred Reporting Items" as a systematic review and meta-analysis of the diagnostic test accuracy (PRISMA-DTA) statement. We searched PubMed, Embase, Web of Science Core Collection, and Cochrane Library up to May 2022 to retrieve non-invasive preimplantation gene detection studies. The eligible research quality was evaluated following the quality assessment study-2 system for diagnostic accuracy. The pooled receiver operator characteristic curve (SROC) and the area under SROC (AUC) were used to evaluate diagnostic performance quantitatively. Threshold effect, subgroup analysis, and meta-regression analysis were used to explore the source of heterogeneity. Deeks' funnel plots and sensitivity analyses were used to test the publication bias and stability of the meta-analysis, respectively.

FINDINGS

Twenty studies met the inclusion criteria. The pooled sensitivity, specificity, and AUC were 0.84 (95% CI 0.72-0.91), 0.85 (95% CI 0.74-0.92), and 0.91 (95% CI 0.88-0.93), respectively. Subgroup analysis showed that the spent culture medium (SCM) subgroup had higher sensitivity and lower specificity than the SCM combined with the blastocoel fluid (BF) subgroup. Subgroup analysis showed that the study sensitivity and specificity of < 100 cases were higher than those of ≥ 100. Heterogeneity (chi-square) analysis revealed that sample size might be a potential source of heterogeneity. Sensitivity analysis and Deeks' funnel plots indicated that our results were relatively robust and free from publication bias.

INTERPRETATION

The present meta-analysis indicated that the pooled sensitivity, specificity, and AUC of niPGT in preimplantation genetic testing were 0.84, 0.85, and 0.91, respectively. niPGT may have high detection accuracy and may serve as an alternative model for embryonic analysis. Additionally, by subgroup analysis, we found that BF did not improve the accuracy of niPGT in embryos. In the future, large-scale studies are needed to determine the detection value of niPGT.

Effectiveness of non-invasive chromosomal screening for normal karyotype and chromosomal rearrangements

Purpose: To study the accuracy of non-invasive chromosomal screening (NICS) results, in normal chromosomes and chromosomal rearrangement groups and to investigate whether using trophoblast cell biopsy along with NICS, to choose embryos for transfer can improve the clinical outcomes of assisted pregnancy.

Methods: We retrospectively analyzed 101 couples who underwent preimplantation genetic testing at our center from January 2019 to June 2021 and collected 492 blastocysts for trophocyte (TE) biopsy. D3-5 blastocyst culture fluid and blastocyst cavity fluid were collected for the NICS. Amongst them, 278 blastocysts (58 couples) and 214 blastocysts (43 couples) were included in the normal chromosomes and chromosomal rearrangement groups, respectively. Couples undergoing embryo transfer were divided into group A, in which both the NICS and TE biopsy results were euploid (52 embryos), and group B, in which the TE biopsy results were euploid and the NICS results were aneuploid (33 embryos).

Results: In the normal karyotype group, concordance for embryo ploidy was 78.1%, sensitivity was 94.9%, specificity was 51.4%, the positive predictive value (PPV) was 75.7%, and the negative predictive value (NPV) was 86.4%. In the chromosomal rearrangement group, concordance for embryo ploidy was 73.1%, sensitivity was 93.3%, specificity was 53.3%, the PPV was 66.3%, and the NPV was 89%. In euploid TE/euploid NICS group, 52 embryos were transferred; the clinical pregnancy rate was 71.2%, miscarriage rate was 5.4%, and ongoing pregnancy rate was 67.3%. In euploid TE/aneuploid NICS group, 33 embryos were transferred; the clinic pregnancy rate was 54.5%, miscarriage rate was 5.6%, and ongoingpregnancy rate was 51.5%. The clinical pregnancy and ongoing pregnancy rates were higher in the TE and NICS euploid group.

Conclusion: NICS was similarly effective in assessing both normal and abnormal populations. Identification of euploidy and aneuploidy alone may lead to the wastage of embryos due to high false positives. More suitable reporting methods for NICS and countermeasures for a high number of false positives in NICS are needed. In summary, our results suggest that combining biopsy and NICS results could improve the outcomes of assisted pregnancy.

Comparing the advantages, disadvantages and diagnostic power of different non-invasive pre-implantation genetic testing: A literature review

To improve embryo transfer success and increase the chances of live birth in assisted reproductive methods, there is a growing demand for the use of pre-implantation genetic testing (PGT). However, the invasive approaches used in PGT have led to in vitrofertilization failure and abortions, increasing anxiety levels for parents. To address this, non-invasive PGT methods have been introduced, such as the detection of DNA in blastocoel fluid of blastocysts and spent culture media (SCM). These methods have proven to be minimally invasive and effective in detecting aneuploidy in the chromosomes of human embryos. This review aims to explore the different approaches to pre-implantation diagnosis, including invasive and non-invasive methods, with a particular focus on non-invasive PGT (niPGT). The search strategy involved gathering data from scientific databases such as PubMed, Google Scholar, and Science Direct using relevant keywords. The search was conducted until January 2023. In total, 22 studies have successfully reported the detection and amplification of cell-free DNA in the embryonic SCM. It is important to note that niPGT has some limitations, which include differences in indicators such as cell-free DNA amplification rate, concordance, level of maternal DNA contamination, sensitivity, and specificity between SCM samples and biopsied cells. Therefore, more extensive and detailed research is needed to fully understand niPGT's potential for clinical applications.

Concordance of PGT for aneuploidies between blastocyst biopsies and spent blastocyst culture medium

RESEARCH QUESTION

Non-invasive preimplantation genetic testing for aneuploidies (niPGT-A) avoids the possible detrimental impact of invasive PGT-A on embryo development and clinical outcomes. Does cell-free DNA (cfDNA) from spent blastocyst culture medium (BCM) reflect embryonic chromosome status better than trophectoderm (TE) biopsy?

DESIGN

In this study, 35 donated embryos were used for research and the BCM, TE biopsy, inner cell mass (ICM) and residual blastocyst (RB) were individually picked up from these embryos. Whole genome amplification (WGA) was performed and amplified DNA was subject to next-generation sequencing. Chromosome status concordance was compared among the groups of samples.

RESULTS

The WGA success rates were 97.0% (TE biopsy), 100% (ICM), 97.0% (RB) and 88.6% (BCM). Using ICM as the gold standard, the chromosomal ploidy concordance rates for BCM, TE biopsy and RB were 58.33% (14/24), 68.75% (22/32) and 78.57% (22/28); the diagnostic concordance rates were 83.33% (20/24), 87.50% (28/32) and 92.86% (26/28); and the sex concordance rates were 92.31% (24/26), 100% (32/32) and 100% (28/28), respectively. Considering RB the gold standard, the chromosome ploidy concordance rates for BCM and TE biopsy were 61.90% (13/21) and 81.48% (22/27); the diagnostic concordance rates were 71.43% (15/21) and 88.89% (24/27); and the sex concordance rates were 91.30% (21/23) and 100% (27/27), respectively.

CONCLUSIONS

The results of niPGT-A of cfDNA of spent BCM are comparable to those of invasive PGT-A of TE biopsies. Modifications of embryo culture conditions and testing methods will help reduce maternal DNA contamination and improve the reliability of niPGT-A.

PGT-A is associated with reduced cumulative live birth rate in first reported IVF stimulation cycles age ≤ 40: an analysis of 133,494 autologous cycles reported to SART CORS

PURPOSE

To evaluate the impact of preimplantation genetic testing for aneuploidy (PGT-A) on cumulative live birth rate (CLBR) in IVF cycles.

METHODS

Retrospective cohort study of the SART CORS database, comparing CLBR for patients using autologous oocytes, with or without PGT-A. The first reported autologous ovarian stimulation cycle per patient between January 1, 2014, and December 31, 2015, and all linked embryo transfer cycles between January 1, 2014, and December 31, 2016, were included in the study. Exclusion criteria were donor oocyte cycles, donor embryo cycles, gestational carrier cycles, cycles which included both a fresh embryo transfer (ET) combined with a thawed embryo previously frozen (ET plus FET), or cycles with a fresh ET after PGT-A.

RESULTS

A total of 133,494 autologous IVF cycles were analyzed. Amongst patients who had blastocysts available for either ET or PGT-A, including those without transferrable embryos, decreased CLBR was noted in the PGT-A group at all ages, except ages > 40 (p < 0.01). A subgroup analysis of only those patients who had PGT-A and a subsequent FET, excluding those without transferrable embryos, demonstrated a very high CLBR, ranging from 71.2% at age < 35 to 50.2% at age > 42. Rates of multiple gestations, preterm birth, early pregnancy loss, and low birth weight were all greater in the non-PGT-A group.

CONCLUSIONS

PGT-A was associated with decreased CLBR amongst all patients who had blastocysts available for ET or PGT-A, except those aged > 40. The negative association of PGT-A use and CLBR per cycle start was especially pronounced at age < 35.

An Update on Non-invasive Approaches for Genetic Testing of the Preimplantation Embryo

Preimplantation Genetic Testing (PGT) aims to reduce the chance of an affected pregnancy or improve success in an assisted reproduction cycle. Since the first established pregnancies in 1990, methodological approaches have greatly evolved, combined with significant advances in the embryological laboratory. The application of preimplantation testing has expanded, while the accuracy and reliability of monogenic and chromosomal analysis have improved. The procedure traditionally employs an invasive approach to assess the nucleic acid content of embryos. All biopsy procedures require high technical skill, and costly equipment, and may impact both the accuracy of genetic testing and embryo viability. To overcome these limitations, many researchers have focused on the analysis of cell-free DNA (cfDNA) at the preimplantation stage, sampled either from the blastocoel or embryo culture media, to determine the genetic status of the embryo non-invasively. Studies have assessed the origin of cfDNA and its application in non-invasive testing for monogenic disease and chromosomal aneuploidies. Herein, we discuss the state-of-the-art for modern non-invasive embryonic genetic material assessment in the context of PGT. The results are difficult to integrate due to numerous methodological differences between the studies, while further work is required to assess the suitability of cfDNA analysis for clinical application.

Majority of transferred mosaic embryos developed healthy live births revealed by a preclinical study using embryonic morphology assessment and noninvasive PGT-A on cell-free DNA in blastocoel fluid

PURPOSE

This preclinical study aimed to evaluate whether using transferred mosaic embryos (primarily selected by embryonic morphology assessment (EMA) and compared by the noninvasive preimplantation genetic testing for aneuploidy (niPGT-A) on cell-free DNA in blastocoel fluid (BF)) increases the rates of clinical pregnancies (CPs) and healthy live births (HLBs) and to investigate whether niPGT-A could provide valuable genetic information for the EMA-selected transferred mosaic embryos.

METHODS

This study collected 215 blastocyst culture samples and 182 BF samples. Cell-free DNA from the BF was amplified and examined by next-generation sequencing-based niPGT-A. All 182 patients underwent EMA. However, only 147 underwent in vitro fertilization and embryo transfer, and only 113 clinical outcomes were followed up. Comprehensive chromosome screening for the chorionic villus sampling of spontaneous miscarriages and noninvasive prenatal testing for ongoing pregnancies were also performed.

RESULTS

The implantation rate was 77.55% in 147 transferred high-quality embryos selected by EMA. Among 113 CPs, 16 led to spontaneous miscarriage (14.16%), and 97 resulted in HLBs (85.84%). According to the niPGT-A results for 113 patients with clinical outcomes, 80.4% had CP (euploid, 20.54%; single aneuploid, 1.79%; mosaic chromosome aneuploid and/or segmental aneuploid, 58.04%). Of all the mosaic aneuploids, 90.76% were false positive, transforming to euploid.

CONCLUSIONS

Transferred EMA-selected embryos showed higher implantation rates. The niPGT-A of BF provided valuable genetic status ("-ploid") information, which helped reduce aneuploid-induced implantation failure and miscarriage, thereby increasing the CP and HLB rates. Additionally, majority of the transferred embryos with complex/chaotic mosaic aneuploid would likely develop HLBs.

Non-invasive preimplantation genetic testing for conventional IVF blastocysts

BACKGROUND

Previous studies suggested that non-invasive preimplantation genetic testing (niPGT) for intracytoplasmic sperm injection (ICSI) blastocysts can be used to identify chromosomal ploidy and chromosomal abnormalities. Here, we report the feasibility and performance of niPGT for conventional in vitro fertilization (IVF) blastocysts.

METHODS

This was a prospective observational study. In the preclinical stage, whole genome amplification and NGS were performed using the sperm spent culture medium (SCM). Then, trophectoderm (TE) biopsies and corresponding SCM derived from 27 conventional IVF monopronuclear embryos were collected. In the clinical stage, samples from 25 conventional IVF cycles and 37 ICSI cycles from April 2020-August 2021 were collected for performance evaluation.

RESULTS

Preclinically, we confirmed failed sperm DNA amplification under the current amplification system. Subsequent niPGT from the 27 monopronuclear blastocysts showed 69.2% concordance with PGT results of corresponding TE biopsies. In the clinical stage, no paternal contamination was observed in any of the 161 SCM samples from conventional IVF. While maternal contamination was observed in 29.8% (48/161) SCM samples, only 2.5% (4/161) samples had a contamination ratio ≥ 50%. Compared with that of TE biopsy, the performances of NiPGT from 161 conventional IVF embryos and 122 ICSI embryos were not significantly different (P > 0.05), with ploidy concordance rates of 75% and 74.6% for IVF and ICSI methods, respectively. Finally, evaluation of the euploid probability of embryos with different types of niPGT results showed prediction probabilities of 82.8%, 77.8%, 62.5%, 50.0%, 40.9% and 18.4% for euploidy, sex-chromosome mosaics only, low-level mosaics, multiple abnormal chromosomes, high-level mosaics and aneuploidy, respectively.

CONCLUSIONS

Our research results preliminarily confirm that the niPGT approach using SCM from conventional IVF has comparable performance with ICSI and might broadening the application scope of niPGT.

Noninvasive Chromosome Screening for Evaluating the Clinical Outcomes of Patients With Recurrent Pregnancy Loss or Repeated Implantation Failure

This retrospective cohort study explores whether noninvasive chromosome screening (NICS) for aneuploidy can improve the clinical outcomes of patients with recurrent pregnancy loss (RPL) or repeated implantation failure (RIF) in assisted reproductive technology. A total of 273 women with a history of RPL or RIF between 2018 and 2021 were included in this study. We collected data of all oocyte retrieval cycles and single blastocyst resuscitation transfer cycles. For the patients experiencing RPL, NICS reduced the miscarriages rate per frozen embryo transfer (FET), improved the ongoing pregnancies rate and live birth rate: 17.9% vs 42.6%, adjusted OR 0.39, 95% CI 0.16-0.95; 40.7% vs 25.0%, adjusted OR 2.00, 95% CI 1.04-3.82; 38.9% vs 20.6%, adjusted OR 2.53, 95% CI 1.28-5.02, respectively. For the patients experiencing RIF, the pregnancy rates per FET in the NICS group were significantly higher than those in the non-NICS group (46.9% vs. 28.7%, adjusted OR 2.82, 95% CI 1.20-6.66). This study demonstrated that the selection of euploid embryos through NICS can reduce the miscarriage rate of patients experiencing RPL and improve the clinical pregnancy rate of patients experiencing RIF. Our data suggested NICS could be considered as a possibly useful screening test in clinical practice.

Validation of Non-Invasive Preimplantation Genetic Screening Using a Routine IVF Laboratory Workflow

Embryo selection is needed to optimize the chances of pregnancy in assisted reproduction technology. This study aimed to validate non-invasive preimplantation genetic testing for aneuploidy (niPGT-A) using a routine IVF laboratory workflow. Can niPGT-A combined with time-lapse morphokinetics provide a better embryo-selection strategy? A total of 118 spent culture mediums (SCMs) from 32 couples were collected. A total of 40 SCMs and 40 corresponding trophectoderm (TE) biopsy samples (n = 29) or arrested embryos (n = 11) were assessed for concordance. All embryos were cultured to the blastocyst stage (day 5 or 6) in a single-embryo culture time-lapse incubator. The modified multiple annealing and looping-based amplification cycle (MALBAC) single-cell whole genome amplification method was used to amplify cell-free DNA (cfDNA) from the SCM, which was then sequenced on the Illumina MiSeq system. The majority of insemination methods were conventional IVF. Low cfDNA concentrations were noted in this study. The amplification niPGT-A and conventional PGT-A was 67.7%. Based on this study, performing niPGT-A without altering the daily laboratory procedures cannot provide a precise diagnosis. However, niPGT-A can be applied in clinical IVF, enabling the addition of blastocysts with a better prediction of euploidy for transfer.

Ploidy Testing of Blastocoel Fluid for Screening May Be Technically Challenging and More Invasive Than That of Spent Cell Culture Media

Background

Recent studies have demonstrated that both blastocoel fluid (BF) and spent cell culture media (SCM) have potential as materials for non-invasive or less-invasive pre-implantation genetic analysis. BF may allow more opportunity to obtain cell-free DNA from the inner cell mass (ICM), and it has a lower risk of containing contaminant DNA from cumulus cells, sperm and culture media. There are no data regarding the ICM as a gold standard to evaluate the chromosome constitution of BF or SCM for embryo liquid biopsy.

Methods

Two hundred eighteen donated human blastocysts were warmed and cultured in blastocyst culture media for 18–24 h. The corresponding SCM was collected, and only clear ICM was biopsied in blastocysts; otherwise, the whole blastocyst (WB) was biopsied. Quantitative PCR was performed to determine the DNA levels in the SCM and BF before and after amplification. ChromInst was used to amplify BF/SCM and blastocyst DNA before sequencing. Chromosomal copy number variation (CNV) was investigated to evaluate the chromosome constitution.

Results

In total, 212 blastocysts were available for SCM and BF collection. The technical success rates (next-generation sequencing data) were 100 and 69.8% (148/212) for SCM and BF, respectively. Among the 148 blastocysts with both SCM and BF data, 101 were euploid and 47 were aneuploid based on ICM (n = 89) or WB (n = 59) analysis as the gold standard. Among all blastocysts, SCM was comparable to BF [specificity: 80.2 versus 61.4% (P = 0.005, χ² test); sensitivity: 91.5 versus 87.2% (P = 0.738, χ² test); negative predictive value (NPV): 95.3 versus 91.2% (P = 0.487, χ² test); positive predictive value (PPV): 68.3% versus 51.3% (P = 0.042, χ² test)]. The SCM and BF samples were 83.8% (124/148) and 69.6% (103/148) concordant with the corresponding ICM/WB samples when only two categories, euploid or aneuploid/mosaic, were grouped to calculate the concordance.

Conclusions

Compared with BF, SCM has superior diagnostic performance, and it is non-invasive for embryos.

Clinical Trial Registration

[http://www.chictr.org.cn], identifier [ChiCTR-BPD-17014087].

First Baby Born in Brazil after Simultaneous Diagnosis through Non-Invasive and Conventional PGT-A

Non-invasive preimplantation genetic testing for aneuploidies (niPGT-A) aiming to assess cell-free embryonic DNA in spent culture media is promising, especially because it might overcome the diminished rates of implantation caused by the inadequate performance of trophectoderm (TE) biopsy. Our center is part of the largest study to date assessing the concordance between conventional PGT-A and niPGT-A, and we report here the delivery of the first baby born in Brazil using niPGT-A. The parents of the baby were admitted to our center in 2018. They did not present history of infertility, and they were interested in using in vitro fertilization (IVF) and PGT-A in order to avoid congenital anomalies in the offspring. A total of 11 (3 day-5 and 8 day-6) expanded blastocysts were biopsied, and the spent culture media (culture from day-4 to day-6) from 8 day-6 blastocysts were collected for niPGT-A. Overall, 7 embryos yielded informative results for trophectoderm (TE) and media samples. Among the embryos with informative results, 5 presented concordant diagnosis between conventional PGT-A and niPGT-A, and 2 presented discordant diagnosis (1 false-positive and one false-negative). The Blastocyst 4, diagnosed as 46, XY by both niPGT-A and conventional PGT-A, was warmed up and transferred, resulting in the birth of a healthy 3.8 kg boy in February 2020. Based on our results and the recent literature, we believe that the safest current application of niPGT-A would be as a method of embryo selection for patients without an indication for conventional PGT-A. The approximate 80% of reliability of niPGT-A in the diagnosis of ploidy is superior to predictions provided by other non-invasive approaches like morphology and morphokinetics selection.

The identification of endometrial immune cell densities and clustering analysis in the mid-luteal phase as predictor for pregnancy outcomes after IVF-ET treatment

Changes in endometrial immune cell density has been reported to be associated with reproductive failure. The prognostic value of endometrial immune cell density measurement remains uncertain. We aimed to investigate the prognostic value of endometrial immune cells measurement on pregnancy outcome after IVF in women. In this prospective study, one hundred twenty-eight women underwent endometrial sampling in a natural cycle preceding single frozen-thawed embryo transfer (ET). Endometrial biopsy was obtained precisely 7 days after luteinizing hormone surge (LH + 7). Multiplex immunohistochemical method was employed to simultaneously stain the endometrium samples with a panel of human antibodies against CD56 for uterine natural killer (uNK) cells, CD3 and CD8 for T cell, CD3 for pan T cells and CD68 for macrophages. The density of the various immune cells and the clustering levels between them were measured. ET was performed at the blastocyst stage. Women who did not conceive had a significantly higher density of uNK cells and higher clustering level between uNK cells-and-macrophages than women who did conceive. In accordance, the prognostic value of uNK measurement on pregnancy outcome was significantly improved when combined with uNK-to-macrophage clustering analysis simultaneously. Taken together, our results suggested that uNK cells density and clustering level between uNK cells-and macrophages may be a promising predictor for successful implantation after IVF-ET.

Preimplantation Genetic Testing for Monogenic Conditions: Is Cell-Free DNA Testing the Next Step?

Genetic assessment of an embryo via preimplantation genetic testing (PGT) represents an important reproductive option for couples wanting to try and improve success rates from in vitro fertilisation (IVF) cycles, as well as reduce their risk of having a child born with a genetic condition. Currently, biopsy of the developing embryo prior to transfer allows genetic assessment of an embryo for either chromosome copy number (aneuploidy [PGT-A] or segmental rearrangement [PGT-SR]) or to avoid the transmission of a single gene condition (monogenic conditions [PGT-M]). However, this technology is invasive and commands considerable resources. Non-invasive PGT (niPGT) offers a potential alternate mode of embryonic analysis. Whilst the utility of niPGT-A has been recently explored, there has been limited consideration of niPGT-M as an option for couples at risk of passing on a single gene or chromosomal condition. This review examines the historical and current clinical context of preimplantation embryonic analysis for monogenic conditions, in addition to important considerations surrounding the origin and analysis of cell-free deoxyribose nucleic acid (cfDNA), whether it is sourced via blastocentesis or spent embryonic culture medium (SCM). Future capabilities of this testing modality will almost certainly be enhanced by integration of whole genome sequencing into everyday practice. In addition, the increased utilisation of reproductive carrier screening as part of standard reproductive healthcare will likely result in the identification of a larger high-risk population. As a result, stratification of limited and highly specialised reproductive genetic resources will be required. Prospective parents should continue to be made aware of the limitations of this technology, with prenatal confirmatory testing remaining an essential part of antenatal care in these patients. However, niPGT-M poses an important alternate testing modality for high-risk couples, particularly in the setting of embryos that cannot be biopsied for traditional PGT-M and as demand for this treatment continues to grow.

A Non-invasive Chromosome Screening Strategy for Prioritizing in vitro Fertilization Embryos for Implantation

Preimplantation genetic testing for aneuploidy (PGT-A) is widely used to select embryos having normal ploidy for transfer, but they require an invasive embryo biopsy procedure that may cause harm to the embryos and offspring. Therefore, a non-invasive approach to select embryos with normal ploidy for implantation is highly demanded. Non-invasive chromosome screening (NICS) methods have been proposed and applied in clinical practices, but a large-scale validation versus invasive preimplantation genetic testing (PGT) and the whole embryo ploidy has not yet been reported. In this study, by using the whole embryo as a gold standard, we validated NICS assay in a total of 265 donated human embryos and compared its performance with conventional trophectoderm (TE) biopsy PGT. The NICS assay showed promising performance, which is comparable to PGT-TE [sensitivity: 87.36 versus 89.66%; specificity: 80.28 versus 82.39%; negative predictive value (NPV): 91.2 versus 92.86%; positive predictive value (PPV): 73.08 versus 75.73%]. Additionally, NICS provides a scoring system for prioritizing embryo: embryos can be categorized into three groups with euploid prediction probabilities of 90.0, 27.8, and 72.2% for group euploid (A), aneuploid (B), and multiple abnormal chromosomes (MAC) (C), respectively. When an addition of TE assay is provided as a secondary validation, the accuracy significantly increases from 72.2 to 84.3% for group B and from 27.8 to 83.3% for group C. Our results suggest that NICS is a good rule in assay for identifying chromosomal normal embryos for transfer and might serve as a non-invasive approach for prioritizing embryos instead of preventing transfer of aneuploid and MAC embryos. It will help to ensure the safety of offspring and efficient utilization of embryos.

Non-invasive preimplantation genetic testing for putative mosaic blastocysts: a pilot study

STUDY QUESTION

What is the potential of applying non-invasive preimplantation genetic testing (niPGT) for chromosome abnormalities in blastocysts reported with a mosaic trophectoderm (TE) biopsy?

SUMMARY ANSWER

niPGT of cell-free DNA in blastocyst culture medium exhibited a good diagnostic performance in putative mosaic blastocysts.

WHAT IS KNOWN ALREADY

Advances in niPGT have demonstrated the potential reliability of cell-free DNA as a resource for genetic assessment, but information on mosaic embryos is scarce because the mosaicism may interfere with niPGT. In addition, the high incidence of mosaicism reported in the context of PGT and the viability of mosaic blastocysts raise questions about whether mosaicism really exists.

STUDY DESIGN, SIZE, DURATION

The study was performed between May 2020 and July 2020. First, clinical data collected by a single-center over a 6-year period on PGT for chromosome aneuploidies (PGT-A) or chromosomal structural rearrangements (PGT-SR) were analyzed. After confirming the reliability of niPGT, 41 blastocysts classified as mosaics by trophectoderm (TE) biopsy were re-cultured. The chromosomal copy number of the blastocyst embryo (BE, the gold standard), TE re-biopsy, and corresponding cell-free DNA in the culture medium was assessed.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Data on patients enrolled for PGT at a single center from 2014 to 2019 were collected and the cycles with available putative mosaic blastocysts were evaluated. To verify the diagnostic validity of niPGT, eight aneuploid blastocysts were thawed and re-cultured for 14-18 h. The concordance of the niPGT diagnosis results and the whole blastocyst testing results was analyzed. Forty-one blastocysts reported as mosaics from 22 patients were included and re-cultured for 14-18 h. The genetic material of the BE, TE re-biopsy, and corresponding cell-free DNA in the culture medium was amplified using multiple annealing and looping-based amplification cycles. The karyotype data from niPGT and TE re-biopsy were compared with that from the whole blastocyst, and the efficiency of niPGT was assessed.

MAIN RESULTS AND THE ROLE OF CHANCE

Data on 3738 blastocysts from 785 PGT-A or PGT-SR cycles of 677 patients were collected. According to the TE biopsy report, of the 3662 (98%) successfully amplified samples, 24 (0.6%) yielded no results, 849 (23.2%) were euploid, 2245 (61.3%) were aneuploid, and 544 (14.9%) were mosaic. Sixty patients without euploid blastocysts opted for a single mosaic blastocyst transfer, and 30 (50%) of them obtained a clinical pregnancy. With the BE chromosome copy number as the gold standard, niPGT and TE re-biopsy showed reliable detection ability and diagnostic efficiency in eight putative aneuploid blastocysts. Of the 41 putative mosaic blastocysts re-cultured and re-tested, 35 (85.4%) showed euploid BE results. All but two of the blastocysts previously diagnosed with segmental chromosomal mosaic were actually euploid. In addition, all blastocysts previously classified as low degree (20-50%) mosaics were identified as euploid by BE PGT, whereas four of the six putative high degree (50-80%) mosaic blastocysts showed chromosomal abnormalities. The raw concordance rates of spent culture medium (SCM) and TE re-biopsies compared with BE were 74.4% and 82%, respectively, in terms of overall ploidy and 96.2% and 97.6%, respectively, per single chromosome when considering all degree mosaic results as true positives. However, when we set a mosaicism identification threshold of 50%, the concordance rates of SCM and TE re-biopsies compared with BE were 87.2% and 85% at the overall ploidy level and 98.8% and 98.3% at the chromosomal level, respectively. At the full ploidy level, the sensitivity and false negative rates for niPGT were 100% and 0, respectively. After adjustment of the threshold for mosaicism, the specificity of niPGT increased from 69.7% to 84.8% in terms of overall ploidy and from 96.1% to 98.9% at the chromosomal level.

LIMITATIONS, REASONS FOR CAUTION

The primary limitation of this study is the small sample size, which decreases the strength of our conclusions. If possible, identifying the clinical outcome of niPGT on reassessed mosaic blastocysts would be further progress in this field.

WIDER IMPLICATIONS OF THE FINDINGS

This study is the first to explore the practicability of niPGT in diagnostic reassessment of putative mosaicism. The present study provides a novel opportunity for patients with only mosaic blastocysts and no euploid blastocysts, regardless of the technical or biological basis of mosaicism. Employing niPGT after 14-18 h of re-culturing might be a superior option for the best use of blastocysts because of its minimally invasive nature.

STUDY FUNDING/COMPETING INTEREST(S)

This work was supported by grants from National Key Technology Research and Development Program of China (No. 2017YFC1002004), the Central Guiding the Science and Technology Development of the Local (2018080802D0081) and College Natural Science Project of Anhui Province (KJ2019A0287). There are no competing interests to declare.

TRIAL REGISTRATION NUMBER

N/A.

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.

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

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

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.

Validation of preimplantation genetic tests for aneuploidy (PGT-A) with DNA from spent culture media (SCM): concordance assessment and implication

BACKGROUND

Spent culture medium (SCM) as a source of DNA for preimplantation genetic tests aneuploidy (PGT-A) has been widely discussed.

METHODS

Seventy-five blastocysts that were donated for research provided a unique possibility in which multiple specimens, including trophectoderm (TE) biopsy, SCM, and paired corresponding whole blastocyst (WB) specimens from the same blastocyst source, could be utilized for the purpose of this preclinical validation.

RESULTS

To conduct a validation ploidy concordance assessment, we evaluated the full chromosomal concordance rates between SCM and WB (SCM-to-WB), and between TE and WB (TE-to-WB) as well as sensitivity, specificity and overall diagnostic accuracy. 78.67% (59/75) of NGS results in the SCM group were interpretable, a significantly lower percentage than their corresponding TE and WB groups. This discrepancy manifests itself in intrinsically low quantity and poor integrity DNA from SCM. Subsequently, remarkable differences in full concordance rates (including mosaicism, and segmental aneuploidies) are seen as follows: 32.2% (SCM-to-WB, 19/59) and 69.33% (TE-to-WB, 52/75), (p < 0.001). In such cases, full concordance rates were 27.27% (15/55) in SCM-to-WB, and, 76% (57/75) in TE-to-WB (p < 0.001). Collectively, the NGS data from SCM also translated into lower sensitivities, Positive Predictive Value (PPV), Negative Predictive Value (NPV), overall diagnostic accuracies, and higher Negative Likelihood Ratio (NLR).

CONCLUSIONS

Our study reveals that DNA is detectable in the majority of SCM samples. Individual chromosomal aberration, such as segmental aneuploidy and mosaicism, can be quantitatively and qualitatively measured. However, TE still provides a more accurate and reliable high-throughput methodology for PGT-A. Meanwhile, cell-free DNA in SCM reporting lacks uniform diagnostic interpretations. Considering that this test is meant to determine which embryos are relegated to be discarded, PGT-A with cell-free DNA in SCM should not be permitted to be applied in routine clinical settings for diagnosis purpose.

NGS-Based Application for Routine Non-Invasive Pre-Implantation Genetic Assessment in IVF

Although non-invasive pre-implantation genetic testing for aneuploidy (NIPGT-A) is potentially appropriate to assess chromosomal ploidy of the embryo, practical application of it in a routine IVF centre have not been started in the absence of a recommendation. Our objective in this study was to provide a comprehensive workflow for a clinically applicable strategy for NIPGT-A based on next-generation sequencing (NGS) technology with the corresponding bioinformatic pipeline. In a retrospective study, we performed NGS on spent blastocyst culture media of Day 3 embryos fertilised with intracytoplasmic sperm injection (ICSI) with quality score on morphology assessment using the blank culture media as background control. Chromosomal abnormalities were identified by an optimised bioinformatics pipeline applying copy number variation (CNV) detecting algorithm. In this study, we demonstrate a comprehensive workflow covering both wet- and dry-lab procedures supporting a clinically applicable strategy for NIPGT-A that can be carried out within 48 h, which is critical for the same-cycle blastocyst transfer. The described integrated approach of non-invasive evaluation of embryonic DNA content of the culture media can potentially supplement existing pre-implantation genetic screening methods.

Cell-free DNA in spent culture medium effectively reflects the chromosomal status of embryos following culturing beyond implantation compared to trophectoderm biopsy

This prospective study evaluated the accuracy of non-invasive preimplantation genetic testing for aneuploidy (niPGT-A) using cell-free DNA in spent culture medium, as well as that of preimplantation genetic testing for aneuploidy (PGT-A) using trophectoderm (TE) biopsy after culturing beyond implantation. Twenty frozen blastocysts donated by 12 patients who underwent IVF at our institution were investigated. Of these, 10 were frozen on day 5 and 10 on day 6. Spent culture medium and TE cells were collected from each blastocyst after thawing, and the embryos were cultured in vitro for up to 10 days. The outgrowths after culturing beyond implantation were sampled and subjected to chromosome analysis using next-generation sequencing. Chromosomal concordance rate, sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), false-positive rate (FPR), and false-negative rate (FNR) of niPGT-A and PGT-A against each outgrowth were analyzed. The concordance rate between the niPGT-A and outgrowth samples was 9/16 (56.3%), and the concordance rate between the PGT-A and outgrowth samples was 7/16 (43.8%). NiPGT-A exhibited 100% sensitivity, 87.5% specificity, 88.9% PPV, 100% NPV, 12.5% FPR, and 0% FNR. PGT-A exhibited 87.5% sensitivity, 77.8% specificity, 87.5% PPV, 75% NPV, 14.3% FPR, and 22.2% FNR. NiPGT-A may be more accurate than PGT-A in terms of ploidy diagnostic accuracy in outgrowths.

Cell-free DNA discoveries in human reproductive medicine: providing a new tool for biomarker and genetic assays in ART

Cell-free DNAs (cfDNAs) are fragmented forms of DNA that are released into extracellular environments. Analyzing them, regarding either concentration or genetic/epigenetic status can provide helpful information about disorders, response to treatments, estimation of success rates, etc. Moreover, since they are presented in body fluids, evaluation of the aforementioned items would be achieved by less/non-invasive methods. In human reproduction field, it is required to have biomarkers for prediction of assisted reproduction techniques (ART) outcome, as well as some non-invasive procedures for genetic/epigenetic assessments. cfDNA is an appropriate candidate for providing the both approaches in ART. Recently, scientists attempted to investigate its application in distinct fields of reproductive medicine that resulted in discovering its applicability for biomarker and genetic/epigenetic analyses. However, due to some limitations, it has not reached to clinical administration yet. In this article, we have reviewed the current reported data with respect to advantages and limitations of cfDNA utilization in three fields of ART, reproduction of male and female, as well as in vitro developed embryos.

Application of convolutional neural network on early human embryo segmentation during in vitro fertilization

Selection of the best quality embryo is the key for a faithful implantation in in vitro fertilization (IVF) practice. However, the process of evaluating numerous images captured by time-lapse imaging (TLI) system is time-consuming and some important features cannot be recognized by naked eyes. Convolutional neural network (CNN) is used in medical imaging yet in IVF. The study aims to apply CNN on day-one human embryo TLI. We first presented CNN algorithm for day-one human embryo segmentation on three distinct features: zona pellucida (ZP), cytoplasm and pronucleus (PN). We tested the CNN performance compared side-by-side with manual labelling by clinical embryologist, then measured the segmented day-one human embryo parameters and compared them with literature reported values. The precisions of segmentation were that cytoplasm over 97%, PN over 84% and ZP around 80%. For the morphometrics data of cytoplasm, ZP and PN, the results were comparable with those reported in literatures, which showed high reproducibility and consistency. The CNN system provides fast and stable analytical outcome to improve work efficiency in IVF setting. To conclude, our CNN system is potential to be applied in practice for day-one human embryo segmentation as a robust tool with high precision, reproducibility and speed.

Preimplantation genetic testing for carriers of BRCA1/2 pathogenic variants

The detection of germline BRCA1/2 pathogenic variant has relevant implications for the patients and their family members. Family planning, prophylactic surgery and the possibility of preimplantation genetic testing for monogenic disorders (PGT-M) to avoid transmittance of pathogenic variants to the offspring are relevant topics in this setting. PGT-M is valuable option for BRCA carriers, but it remains a controversial and underdiscussed topic. Although the advances in PGT technologies have improved pregnancy rate, there are still several important challenges associated with its use. The purpose of this review is to report the current evidence on PGT-M for BRCA1/2 carriers, ethical concerns and controversy associated with its use, reproductive implications of BRCA pathogenic variants, underlying areas in which an educational effort would be beneficial as well as possibilities for future research efforts in the field.

Comparative analysis of cell-free DNA content in culture medium and mitochondrial DNA copy number in porcine parthenogenetically activated embryos

We examined the effect of ploidy on mitochondrial DNA (mtDNA) copy number in embryos and the amount of cell-free mitochondrial and nucleic DNA content (cf-mtDNA and cf-nDNA) in spent culture medium (SCM). Oocytes collected from the ovaries were matured, activated, incubated in medium containing cycloheximide (CHX) or CHX and cytochalasin B (CB) for 4.5 h to produce haploid or diploid embryos (H-group and D-group embryos). These embryos were cultured for 7 days, and the blastocysts and SCM were examined. The amount of mtDNA and nDNA was determined by real-time PCR. The rate of development to the blastocyst stage was higher for the D-group than for the H-group. Moreover, D-group blastocysts had less mtDNA compared to the H-group blastocysts. After activation, the mitochondrial content was constant before the blastocyst stage in D-group embryos, but increased earlier in H-group embryos. The amount of cf-mtDNA in the SCM of D-group blastocysts was greater than that of H-group blastocysts. However, when the cf-mtDNA in the SCM of 2 cell-stage embryos (day 2 post-activation) was examined, the amount of cf-mtDNA was greater in the H-group than in the D-group embryos. When D-group embryos were cultured for 7 days, a significant correlation was observed between the total cell number of blastocysts and cf-nDNA content in the SCM. Hence, although careful consideration is needed regarding the time point for evaluating mtDNA content in the embryos and SCM, this study demonstrates that mtDNA in the embryos and SCM was affected by the ploidy of the embryos.

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.

Consistent results of non-invasive PGT-A of human embryos using two different techniques for chromosomal analysis

RESEARCH QUESTION

Are discordances in non-invasive preimplantation genetic testing for aneuploidies (niPGT-A) results attributable to the technique used for chromosomal analysis?

DESIGN

A prospective blinded study was performed (September 2018 to December 2019). In total 302 chromosomal analyses were performed: 92 trophectoderm PGT-A biopsies and their corresponding spent embryo culture medium (SCM) evaluated by two methods (n = 184), negative controls (n = 8), and trophectoderm and inner cell mass biopsies from trophectoderm-aneuploid embryos (n = 18). Trophectoderm analyses were carried out using Veriseq (Illumina), and SCM was analysed using Veriseq and NICS (Yikon).

RESULTS

Genetic results were obtained for 96.8% of trophectoderm samples versus 92.4% for both SCM techniques. The mosaicism rate was higher for SCM regardless of the technique used: 30.4% for SCM-NICS and 28.3% for SCM-Veriseq versus 14.1% for trophectoderm biopsies (P = 0.013, P = 0.031, respectively). No significant differences in diagnostic concordance were seen between the two SCM techniques (74.6% for SCM-NICS versus 72.3% for SCM-Veriseq; P = 0.861). For embryos biopsied on day 6, these rates reached 92.0% and 86.5%, respectively. On reanalysing trophectoderm-aneuploid embryos, the discrepancies were shown to be due to maternal DNA contamination (55.6%; 5/9), embryo mosaicism (22.2%; 2/9) and low resolution in SCM-NICS (11.1%; 1/9) and in both SCM techniques (11.1%; 1/9).

CONCLUSIONS

This is the first study evaluating the consistency of different chromosomal analysis techniques for niPGT-A. In conclusion, the diagnostic concordance between PGT-A and niPGT-A seems independent of the technique used. Optimization of culture conditions and medium retrieval provides a potential target to improve the reliability of niPGT-A.

Multicenter prospective study of concordance between embryonic cell-free DNA and trophectoderm biopsies from 1301 human blastocysts

BACKGROUND

The recent identification of embryonic cell-free DNA in spent blastocyst media has opened a new era of possibilities for noninvasive embryo aneuploidy testing in assisted reproductive technologies. Yet, previous studies assessing a limited number of embryos reported variable concordance between embryonic cell-free DNA and trophectoderm biopsies, thus questioning the validity of this approach.

OBJECTIVE

This study aimed to evaluate the concordance and reproducibility of testing embryonic cell-free DNA vs trophectoderm DNA obtained from the same embryo in a large sample of human blastocysts and to assess the contribution of the inner cell mass and trophectoderm to embryonic cell-free DNA released to the culture media.

STUDY DESIGN

This is an interim analysis of a prospective, observational study among 8 in vitro fertilization centers in 4 continents to assess consistency between noninvasive embryo aneuploidy testing of embryonic cell-free DNA and conventional trophectoderm biopsy. The analysis included 1301 day-6/7 blastocysts obtained in 406 in vitro fertilization cycles from 371 patients aged 20-44 years undergoing preimplantation genetic testing for aneuploidy. Fresh oocytes underwent intracytoplasmic sperm injection or in vitro fertilization. No previous assisted hatching or vitrification was allowed before media collection. Individual spent blastocyst medium was collected from embryos cultured at least 40 hours from day 4. After media collection, conventional preimplantation genetic testing for aneuploidy, comprising trophectoderm biopsy and blastocyst vitrification, was performed. Embryonic cell-free DNA was analyzed blindly after embryo transfer. Inner cell mass and trophectoderm biopsies were also performed in a subset of 81 aneuploid blastocysts donated for research.

RESULTS

Embryonic cell-free DNA analyses were 78.2% (866/1108) concordant with the corresponding trophectoderm biopsies. No significant differences were detected among centers ranging from 72.5% to 86.3%. Concordance rates exceeded 86% when all defined steps in the culture laboratory were controlled to minimize the impact of maternal and operator contamination. Sensitivity per center ranged from 76.5% to 91.3% and specificity from 64.7% to 93.3%. The false-negative rate was 8.3% (92/1108), and false-positive rate was 12.4% (137/1108). The 2 fertilization techniques provided similar sensitivity (80.9% vs 87.9%) and specificity (78.6% vs 69.9%). Multivariate analysis did not reveal any bias from patient clinical background, ovarian stimulation protocols, culture conditions, or embryo quality on testing accuracy of concordance. Moreover, concordances of embryonic cell-free DNA with trophectoderm and inner cell mass suggest that the embryonic cell-free DNA originates from both compartments of the human embryo.

CONCLUSION

Noninvasive analysis of embryonic cell-free DNA in spent blastocyst culture media demonstrates high concordance with trophectoderm biopsy results in this large multicenter series. A noninvasive approach for prioritizing embryo euploidy offers important advantages such as avoiding invasive embryo biopsy and decreased cost, potentially increasing accessibility for a wider patient population.

Noninvasive Preimplantation Genetic Testing for Aneuploidy (niPGT-A): The first Brazilian baby

Recently, a new technology known as the Noninvasive Preimplantation Genetic Testing for Aneuploidy (niPGT-A) emerged, using cell-free DNA present in the spent culture media of human blastocysts. Unlike PGT-A, in which only trophectoderm cells are used, niPGT-A reflects the ploidy state of these cells and internal cell mass, suggesting that this new technology may be less prone to error, being more reliable than the invasive test. The aim of the present study was to report the first occurrence of childbirth following niPGT-A in Brazil.

Diagnostic efficiency of blastocyst culture medium in noninvasive preimplantation genetic testing

Objective

To evaluate the diagnostic efficiency of spent blastocyst culture medium (BCM) in noninvasive preimplantation genetic testing (niPGT) by comparing the karyotype concordance with corresponding inner cell mass (ICM) among initial trophectoderm (TE) biopsy, TE re-biopsy, and BCM sampling.

Design

Re-analysis aneuploid/mosaic blastocysts donated for research by couples.

Setting

Institutional in vitro fertilization center.

Patient(s)

A total of 12 couples donated their blastocysts, which had previously been diagnosed as aneuploid or mosaic by initial TE-biopsy preimplantation genetic testing for aneuploidy (PGT-A) for research.

Intervention(s)

A total of 26 frozen−thawed blastocysts were re-analyzed by TE re-biopsy, ICM biopsy, and the collection of spent BCM.

Main Outcome Measure(s)

Karyotype concordance rates.

Result(s)

For 23 embryos diagnosed as aneuploid by initial TE biopsy, 78.3% of initial TE samples, 87.0% of TE re-biopsies samples, and 78.3% of BCM samples were concordant with corresponding ICM samples, and for three mosaic embryos, the concordance rates with ICM of these three groups were 0%, 100%, and 100%, respectively. With the corresponding ICM result as the true result, sensitivity of both niPGT-A and initial TE were 100%; however, the false-positive rate (FPR) of initial TE was higher than that of niPGT-A (100% vs. 0).

Conclusion(s)

niPGT-A using BCM had diagnostic efficiency similar to that of TE-biopsy PGT-A. In the case of mosaic embryos, niPGT-A using BCM may be more reliable for predicting karyotypes of ICM than initial TE biopsy.

Non-invasive preimplantation genetic testing (niPGT): the next revolution in reproductive genetics?

BACKGROUND

Preimplantation genetic testing (PGT) encompasses methods that allow embryos to be tested for severe inherited conditions or for chromosome abnormalities, relevant to embryo health and viability. In order to obtain embryonic genetic material for analysis, a biopsy is required, involving the removal of one or more cells. This invasive procedure greatly increases the costs of PGT and there have been concerns that embryo viability could be compromised in some cases. The recent discovery of DNA within the blastocoele fluid (BF) of blastocysts and in spent embryo culture media (SCM) has led to interest in the development of non-invasive methods of PGT (niPGT).

OBJECTIVE AND RATIONALE

This review evaluates the current scientific evidence regarding non-invasive genetic assessment of preimplantation embryos. The success of different PGT methodologies in collecting and analysing extra-embryonic DNA is evaluated, and consideration is given to the potential biological and technical hindrances to obtaining a reliable clinical diagnosis.

SEARCH METHODS

Original research and review papers concerning niPGT were sourced by searching PubMed and Google Scholar databases until July 2019. Searches comprised the keywords: 'non-invasive'; 'cell-free DNA'; 'blastocentesis'; 'blastocoel fluid'; 'spent culture media'; 'embryo culture medium'; 'preimplantation genetic testing'; 'preimplantation genetic diagnosis'; 'preimplantation genetic screening'; and 'aneuploidy'.

OUTCOMES

Embryonic DNA is frequently detectable in BF and SCM of embryos produced during IVF treatment. Initial studies have achieved some success when performing cytogenetic and molecular genetic analysis. However, in many cases, the efficiency has been restricted by technical complications associated with the low quantity and quality of the DNA. Reported levels of ploidy agreement between SCM/BF samples and biopsied embryonic cells vary widely. In some cases, a discrepancy with respect to cytogenetic data obtained after trophectoderm biopsy may be attributable to embryonic mosaicism or DNA contamination (usually of maternal origin). Some research indicates that aneuploid cells are preferentially eliminated from the embryo, suggesting that their DNA might be over-represented in SCM and BF samples; this hypothesis requires further investigation.

WIDER IMPLICATIONS

Available data suggest that BF and SCM samples frequently provide DNA templates suitable for genetic analyses, offering a potential means of PGT that is less expensive than traditional methods, requires less micromanipulation skill and poses a lower risk to embryos. Critically, DNA isolation and amplification protocols must be optimised to reproducibly obtain an accurate clinical diagnosis, whilst minimising the impact of confounding factors such as contamination. Further investigations are required to understand the mechanisms underlying the release of embryonic DNA and to determine the extent to which this material reflects the true genetic status of the corresponding embryo. Currently, the clinic al potential of niPGT remains unknown.

The Pregnancy Outcome of Mosaic Embryo Transfer: A Prospective Multicenter Study and Meta-Analysis

Chromosomal mosaicism is at high occurrence in early developmental-stage embryos, but much lower in those at prenatal stage. Recent studies provided evidence on the viability of mosaic embryos by reporting pregnancy outcomes. Expanded research is warranted to evaluate its clinical significance. This is a multi-center prospective cohort study on 137 mosaic, 476 euploid and 835 non-preimplantation genetic testing (non-PGT) embryos from three in vitro fertilization (IVF) providers of three countries in Asia, applying the same preimplantation genetic testing for aneuploidies (PGT-A) reporting criteria. Mosaic embryo transfers (METs) resulted in a significantly lower clinical pregnancy rate (40.1% versus 59.0% versus 48.4%), lower ongoing/live birth rate (27.1% versus 47.0% versus 35.1%) and higher miscarriage rate (33.3% versus 20.5% versus 27.4%) than euploid and non-PGT transfers, respectively. Pregnancy losses after METs were different between embryos carrying numerical and segmental chromosomal abnormalities (p = 0.04). Our meta-analysis concluded that METs gave rise to pregnancies but were associated with a reduced ongoing/live birth rate and a higher miscarriage rate. All 37 MET live births were confirmed viable, among which 8 completed prenatal genetic testing with normal results. Longitudinal investigation on one MET pregnancy evidenced the aneuploidy depletion hypothesis. This is the first multi-center prospective study reporting a full MET pregnancy outcome with complementary information from prenatal genetic testing as compared to euploid and non-PGT cohorts.

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.

Zygotic splitting following embryo biopsy: a cohort study of 207 697 single-embryo transfers following IVF treatment

OBJECTIVE

To evaluate the risk of monozygotic splitting with embryo biopsy during in vitro fertilisation (IVF).

DESIGN

A cohort study.

SETTING

Anonymised assisted reproductive technology national data from the Human Fertilisation and Embryology Authority, UK.

POPULATION

Women undergoing single-embryo transfer (SET) following either pre-implantation genetic testing (PGT) involving embryo biopsy or IVF without PGT.

METHODS

Data on women undergoing SET either following PGT and non-PGT IVF treatment in 2000-2016 were analysed to compare the risk of zygotic splitting and monozygotic twining. Logistic regression analysis was performed adjusting for potential confounders.

MAIN OUTCOMES

Monozygotic spitting, monozygotic twin birth.

RESULTS

Data comprising a total of 207 697 SET cycles (4544 following PGT and 203 153 following non-PGT IVF) were analysed. The live birth rate per embryo transfer was 31.9% (95% confidence interval [CI] 30.5-33.2%) following PGT and 26.9% (95% CI 26.7-27.1%) following non-PGT IVF. The incidence of zygotic splitting following PGT was 2.4% (95% CI 1.7-3.3%) versus 1.5% (95% CI 1.4-1.6%) following non-PGT IVF. There was a significantly higher risk of zygotic splitting with PGT versus non-PGT IVF cycles (odds ratio [OR] 1.64, 95% CI 1.19-2.27). The higher risk of zygotic splitting with PGT cycles remained significant after adjusting for potential confounders (adjusted OR 1.51, 95% CI 1.06-2.15).

CONCLUSIONS

The present study demonstrated an increased risk of monozygotic splitting with embryo biopsy. Given the current sparse literature, it is important to accumulate further evidence to validate the findings.

TWEETABLE ABSTRACT

A likely increased risk of monozygotic splitting following embryo biopsy.