Comprehensive Chromosome Screening Research Articles

Human embryos with segmental aneuploidies display delayed early development: a multi-centre morphokinetic analysis.

ObjectivesTo assess if segmental aneuploid embryos display unique morphokinetic patterns DesignRetrospective multicentre study including a total of 7,027 embryos cultured between 2016 and 2021 in 3 European IVF centres. Analysis was performed on aggregated multicentre data and separately for data from each centre. Embryos with no more than 4 chromosomal alterations were considered in the analysis, resulting in 3,040 euploids, 2,818 whole-chromosome and 697 segmental aneuploids. Overall, the dataset contained 3,742 distinct euploid-segmental sibling pairs. SubjectsStandard morphokinetic features were annotated using various time-lapse systems. Blastocysts were subjected to comprehensive chromosomal screening via PGT-A. ExposureMorphokinetic patterns were compared among euploid, whole-chromosome aneuploid, and segmental aneuploid embryos. Main outcomes measuresMorphokinetic timings across groups were compared using statistical analysis and associations with cleavage features were assessed. Multi-centre and centre-specific multivariate logistic regression models were calibrated, and their predictive performance was evaluated on independent test set data using Area-Under-ROC curve metrics. ResultsSegmental aneuploid embryos cleaved significantly slower than their euploid siblings across the first three cell cycles, with a delay reaching the blastocyst stage of development. Specifically during these early cell cycles, segmental aneuploid embryos were also shown to be significantly slower than their aneuploid siblings . A logistic model based on morphokinetic data from the multicentre dataset and regressed against type of aneuploidy displayed modest predictive performance on an independent test set (train-AUROC=0.58; test-AUROC=0.57). Predictive performance improved based on data from a single centre displaying adequate predictive performance on an independent test set from the same centre (train-AUROC=0.74; test-AUROC=0.64). However, the predictive value diminished when tested on data from other centres (AUROC=0.52-0.55). Finally, the presence of multinucleation and blastomere exclusion at cleavage stage, were associated with segmental aneuploidies. The combination of morphokinetic features and these discrete embryo morphological features into the logistic regression model (train AUROC=0.71) provided an improved prediction of segmental aneuploidy, supporting future investigations using more comprehensive annotation systems. ConclusionThe developed predictive framework might help improve decision-making in PGT-A cycles, helping in the evaluation of embryos showing segmental aneuploidy and distinguishing which embryos are more likely to not have lethal uniform aneuploidies for transfer.

Aligning genotyping and copy number data in single trophectoderm biopsies for aneuploidy prediction: uncovering incomplete concordance.

To what extent can genotype analysis aid in the classification of (mosaic) aneuploid embryos diagnosed through copy number analysis of a trophectoderm (TE) biopsy? In a small portion of embryos, genotype analysis revealed signatures of meiotic or uniform aneuploidy in those diagnosed with intermediate copy number changes, and signatures of presumed mitotic or putative mosaic aneuploidy in those diagnosed with full copy number changes. Comprehensive chromosome screening (CCS) for preimplantation genetic testing has provided valuable insights into the prevalence of (mosaic) chromosomal aneuploidy at the blastocyst stage. However, diagnosis of (mosaic) aneuploidy often relies solely on (intermediate) copy number analysis of a single TE biopsy. Integrating genotype information allows for independent assessment of the origin and degree of aneuploidy. Yet, studies aligning both datasets to predict (putative mosaic) aneuploidy in embryos remain scarce. A single TE biopsy was collected from 1560 embryos derived from 221 couples tested for a monogenic disorder (n = 218) or microdeletion-/microduplication syndrome (n = 3). TE samples were subjected to both copy number and genotyping analysis. Copy number and SNP genotyping analysis were conducted using GENType. Unbalanced chromosomal anomalies ≥10 Mb (or ≥20 Mb for copy number calls <50%) were classified by degree, based on low-range intermediate (LR, 30-50%), high-range intermediate (HR, 50-70%) or full (>70%) copy number changes. These categories were further subjected to genotyping analysis to ascertain the origin (and/or degree) of aneuploidy. For chromosomal gains, the meiotic division of origin (meiotic I/II versus non-meiotic or presumed mitotic) was established by studying the haplotypes. The level of monosomy (uniform versus putative mosaic) in the biopsy could be ascertained from the B-allele frequencies. For segmental aneuploidies, genotyping was restricted to deletions. Of 1479 analysed embryos, 24% (n = 356) exhibited a whole-chromosome aneuploidy, with 19% (n = 280) showing full copy number changes suggestive of uniform aneuploidy. Among 258 embryos further investigated by genotyping, 95% of trisomies with full copy number changes were identified to be of meiotic origin. For monosomies, a complete loss of heterozygosity (LOH) in the biopsy was observed in 97% of cases, yielding a 96% concordance rate at the embryo level (n = 248/258). Interestingly, 4% of embryos (n = 10/258) showed SNP signatures of non-meiotic gain or putative mosaic loss instead. Meanwhile, 5% of embryos (n = 76/1479) solely displayed HR (2.5%; n = 37) or LR (2.6%; n = 39) intermediate copy number changes, with an additional 2% showing both intermediate and full copy number changes. Among embryos with HR intermediate copy number changes where genotyping was feasible (n = 25/37), 92% (n = 23/25) showed SNP signatures consistent with putative mosaic aneuploidy. However, 8% (n = 2/25) exhibited evidence of meiotic trisomy (9%) or complete LOH in the biopsy (7%). In the LR intermediate group, 1 of 33 (3%) genotyped embryos displayed complete LOH. Furthermore, segmental aneuploidy was detected in 7% of embryos (n = 108/1479) (or 9% (n = 139) with added whole-chromosome aneuploidy). These errors were often (52%) characterized by intermediate copy number values, which closely aligned with genotyping data when examined (94-100%). N/A. The findings were based on single TE biopsies and the true extent of mosaicism was not validated through embryo dissection. Moreover, evidence of absence of a meiotic origin for a trisomy should not be construed as definitive proof of a mitotic error. Additionally, a genotyping diagnosis was not always attainable due to the absence of a recombination event necessary to discern between meiotic II and non-meiotic trisomy, or the unavailability of DNA from both parents. Interpreting (intermediate) copy number changes of a single TE biopsy alone as evidence for (mosaic) aneuploidy in the embryo remains suboptimal. Integrating genotype information alongside the copy number status could provide a more comprehensive assessment of the embryo's genetic makeup, within and beyond the single TE biopsy. By identifying meiotic aberrations, especially in presumed mosaic embryos, we underscore the potential value of genotyping analysis as a deselection tool, ultimately striving to reduce adverse clinical outcomes. L.D.W. was supported by the Research Foundation Flanders (FWO; 1S74621N). M.B., K.T., F.V.M., S.J., A.V.T., V.S., D.S., A.D., and S.S. are supported by Ghent University Hospital. B.M. was funded by Ghent University. The authors have no conflicts of interest.

Comprehensive preimplantation genetic testing for balanced insertional translocation carriers

BackgroundBalanced insertional translocations (BITs) can increase the risk of infertility, recurrent miscarriages or neonatal birth defects due to chromosomal imbalances in gametes. However, studies on preimplantation genetic testing (PGT) for...

P-525 Is there an impact of chromosomal structural rearrangements on IVF laboratory outcomes in PGT-SR cycles? a propensity score matching-based study

Abstract Study question Are IVF laboratory outcomes altered in PGT-SR cycles, and how are these outcomes affected by the type of rearrangement and the carrier’s gender? Summary answer PGT-SR cycles showed a decrease in overall blastulation and top-quality blastocyst rates compared to PGT-A cycles. Transferable blastocyst rate correlates with chromosomal structural rearrangement type. What is known already Chromosomal structural rearrangements (SR) are associated with altered gametogenesis, resulting in the formation of gametes with chromosomal imbalances. For affected couples, undergoing IVF cycles with PGT-SR is recommended to select embryos with a normal or balanced karyotype. Scarce data exist on IVF laboratory outcomes in couples undergoing PGT-SR cycles. Findings regarding blastocyst rate, mainly focused on high-quality blastocysts, remain unclear. In addition, structural rearrangement carriers yield fewer transferable blastocysts than patients undergoing PGT-A. Conclusive evidence regarding the influence of carrier gender and type of chromosomal SR on the development of transferable blastocysts is lacking, with existing studies yielding contradictory results. Study design, size, duration This retrospective cohort study was conducted at a single university-affiliated obstetrics and fertility center between January 2019 and November 2023. The analysis involved 558 patients undergoing IVF cycles, including 136 in PGT-SR and 422 in PGT-A cycles. Participants/materials, setting, methods Trophectoderm biopsies from day 5/6/7 blastocysts underwent comprehensive chromosome screening utilizing validated NGS. Propensity Score Matching with a 1:1 match ratio was performed to balance baseline characteristics between the PGT-SR and PGT-A groups. The impact of chromosomal structural rearrangements on laboratory outcomes was assessed using a logistic regression model. Subsequently, within the PGT-SR population, the association between the carrier’s gender and the transferable blastocyst rate was evaluated through logistic regression, adjusting for potential confounders. Main results and the role of chance There was no significant difference in the fertilization rate between the PGT-A and PGT-SR groups (OR = 1.26, 95% CI 1.01-1.60, p-value=0.14). However, the PGT-SR group exhibited a significantly lower overall blastulation rate (36.7%) compared to the PGT-A group (42.8%) (OR = 0.76, 95% CI 0.63-0.93, p-value=0.03). Notably, a significant difference was observed in the top-quality blastocyst rate, with PGT-A patients showing a rate of 21.7% versus 9.57% in PGT-SR patients (OR = 0.45, 95% CI 0.29-0.69, p-value&amp;lt;0.01). In the PGT-SR cohort, female carriers constituted 44.1%, while male carriers were 56.6%. Reciprocal translocations represented 56.5% of the structural rearrangements, with the remaining 43.5% being other types. When comparing female to male carriers, no significant association was observed between the transferable blastocyst rate and the carrier’s gender (OR = 0.90, 95% CI = 0.35-2.31, p-value=0.83). However, a notable association was identified between the transferable blastocyst rate and the type of structural chromosomal rearrangements (OR = 0.16, 95% CI = 0.09-0.29, p-value&amp;lt;0.01). Specifically, in cases where the patient carried a chromosomal SR other than reciprocal translocation, the transferable blastocyst rate was 83.2%, in contrast to 44.9% in patients with reciprocal translocations. Limitations, reasons for caution The retrospective design of this study represents a limitation, and the limited sample size of patients with structural chromosomal rearrangements restricts the statistical power. Wider implications of the findings These findings reveal that patients with SR yield fewer embryos for biopsy than those undergoing PGT-A, showing a reduced rate of transferable blastocysts in cases of reciprocal translocations. Consequently, providing comprehensive counseling and managing expectations for couples undergoing PGT-SR is essential. Trial registration number not applicable

Preimplantation Genetic Testing for Aneuploidy in In Vitro Fertilization Using Comprehensive Chromosome Screening: A Systematic Review and Meta-Analysis.

The utility of pre-implantation genetic testing (PGT-A) is controversial, with older meta-analyses demonstrating improved pregnancy outcomes, while newer trials have not shown benefit. Therefore, we performed a meta-analysis which aimed to evaluate the benefits of PGT-A using comprehensive chromosome screening (CCS) and its effects on in vitro fertilization (IVF) outcomes among randomized controlled trials (RCTs). We conducted a systematic search to identify RCTs comparing women undergoing PGT-A with CSS with women not undergoing PGT-A, from inception to December 2020. Random effects meta-analysis was utilized to calculate average odds ratios (OR) for clinical pregnancy rate (CPR), ongoing pregnancy rate (OPR), and miscarriage rate (MR). The heterogeneity of exposure was assessed using Forest plots and I2 statistics. Publication bias was evaluated using Egger's test. Among 1251 citations, seven RCTs met the inclusion criteria. Biopsies of embryos were carried out at various developmental stages, including polar body, day 3, and day 5-6 of culture. Data was analyzed as all studies and blastocyst only. Meta-analysis failed to show improvement in OPRs using PGT-A in the all ages, <35 years old and ≥35 years old age groups. There was also no significant difference in CPRs in any group. The MR decreased with the use of PGT-A (among all biopsy types and among blastocyst biopsies) in the all-ages group, but not when stratifying according to patient age <35 and ≥35 years old. More data regarding the risks and advantages of PGT-A are needed to make a final decision on the value of this intervention in clinical practice. The exact magnitude of the benefit of PGT-A selection cannot be correctly determined until multiple standardized protocol IVF PGT-A trials are conducted.

Does recurrent implantation failure exist? Prevalence and outcomes of five consecutive euploid blastocyst transfers in 123987 patients.

What are the clinical pregnancy and live birth rates in women who underwent up to two more euploid blastocyst transfers after three failures in the absence of another known factor that affects implantation? The fourth and fifth euploid blastocyst transfers resulted in similar live birth rates of 40% and 53.3%, respectively, culminating in a cumulative live birth rate of 98.1% (95% CI = 96.5-99.6%) after five euploid blastocyst transfers. The first three euploid blastocysts have similar implantation and live birth rates and provide a cumulative live birth rate of 92.6%. An international multi-center retrospective study was conducted at 25 individual clinics. The study period spanned between January 2012 and December 2022. A total of 123987 patients with a total of 64572 euploid blastocyst transfers were screened for inclusion. Patients with a history of any embryo transfer at another clinic, history of any unscreened embryo transfer at participating clinics, parental karyotype abnormalities, the use of donor oocytes or a gestational carrier, untreated intracavitary uterine pathology (e.g. polyp, leiomyoma), congenital uterine anomalies, adenomyosis, communicating hydrosalpinx, endometrial thickness <6 mm prior to initiating of progesterone, use of testicular sperm due to non-obstructive azoospermia in the male partner, transfer of an embryo with a reported intermediate chromosome copy number (i.e. mosaic), preimplantation genetic testing cycles for monogenic disorders, or structural chromosome rearrangements were excluded. Ovarian stimulation protocols and embryology laboratory procedures including trophectoderm biopsy followed the usual practice of each center. The ploidy status of blastocysts was determined with comprehensive chromosome screening. Endometrial preparation protocols followed the usual practice of participating centers and included programmed cycles, natural or modified natural cycles. A total of 105 (0.085% of the total population) patients met the criteria and underwent at least one additional euploid blastocyst transfer after failing to achieve a positive pregnancy test with three consecutive euploid blastocyst transfers. Outcomes of the fourth and fifth euploid blastocyst transfers were similar across participating centers. Overall, the live birth rate was similar with the fourth and fifth euploid blastocysts (40% vs 53.3%, relative risk = 1.33, 95% CI = 0.93-1.9, P value = 0.14). Sensitivity analyses excluding blastocysts biopsied on Day 7 postfertilization, women with a BMI >30 kg/m2, cycles using non-ejaculate or donor sperm, double-embryo transfer cycles, and cycles in which the day of embryo transfer was modified due to endometrial receptivity assay test result yielded similar results. Where data were available, the fourth euploid blastocyst had similar live birth rate with the first one (relative risk = 0.84, 95% CI = 0.58-1.21, P = 0.29). The cumulative live birth rate after five euploid blastocyst transfers was 98.1% (95% CI = 96.5-99.6%). Retrospective design has its own inherent limitations. Patients continuing with a further euploid embryo transfer and patients dropping out from treatment after three failed euploid transfers can be systematically different, perhaps with regard to ovarian reserve or economic status. Implantation failure seems to be mainly due to embryonic factors. Given the stable and high live birth rates up to five euploid blastocysts, unexplained recurrent implantation failure should have a prevalence of <2%. Proceeding with another embryo transfer can be the best next step once a known etiology for implantation failure is ruled out. None. N/A.

The severity of meiotic aneuploidy is associated with altered morphokinetic variables of mouse oocyte maturation.

Is there an association between morphokinetic variables of meiotic maturation and the severity of aneuploidy following in vitro maturation (IVM) in the mouse? The severity of meiotic aneuploidy correlates with an extended time to first polar body extrusion (tPB1) and duration of meiosis I (dMI). Morphokinetic variables measured using time-lapse technology allow for the non-invasive evaluation of preimplantation embryo development within clinical assisted reproductive technology (ART). We recently applied this technology to monitor meiotic progression during IVM of mouse gametes. Whether there is a relationship between morphokinetic variables of meiotic progression and aneuploidy in the resulting egg has not been systematically examined at the resolution of specific chromosomes. Next-generation sequencing (NGS) is a robust clinical tool for determining aneuploidy status and has been reverse-translated in mouse blastocysts and oocytes. Therefore, we harnessed the technologies of time-lapse imaging and NGS to determine the relationship between the morphokinetics of meiotic progression and egg aneuploidy. Cumulus-oocyte complexes were collected from large antral follicles from hyperstimulated CD-1 mice. Cumulus cells were removed, and spontaneous IVM was performed in the absence or presence of two doses of Nocodazole (25 or 50 nM) to induce a spectrum of spindle abnormalities and chromosome segregation errors during oocyte meiosis. Comprehensive chromosome screening was then performed in the resulting eggs, and morphokinetic variables and ploidy status were compared across experimental groups (control, n = 11; 25 nM Nocodazole, n = 13; 50 nM Nocodazole, n = 23). We monitored IVM in mouse oocytes using time-lapse microscopy for 16 h, and time to germinal vesicle breakdown (tGVBD), tPB1, and dMI were analyzed. Following IVM, comprehensive chromosome screening was performed on the eggs and their matched first polar bodies via adaptation of an NGS-based preimplantation genetic testing for aneuploidy (PGT-A) assay. Bioinformatics analysis was performed to align reads to the mouse genome and determine copy number-based predictions of aneuploidy. The concordance of each polar body-egg pair (reciprocal errors) was used to validate the results. Ploidy status was categorized as euploid, 1-3 chromosomal segregation errors, or ≥4 chromosomal segregation errors. Additionally, aneuploidy due to premature separation of sister chromatids (PSSC) versus non-disjunction (NDJ) was distinguished. We applied and validated state-of-the-art NGS technology to screen aneuploidy in individual mouse eggs and matched polar bodies at the chromosome-specific level. By performing IVM in the presence of different doses of Nocodazole, we induced a range of aneuploidy. No aneuploidy was observed in the absence of Nocodazole (0/11), whereas IVM in the presence of 25 and 50 nM Nocodazole resulted in an aneuploidy incidence of 7.69% (1/13) and 82.61% (19/23), respectively. Of the aneuploid eggs, 5% (1/20) was due to PSSC, 65% (13/20) to NDJ, and the remainder to a combination of both. There was no relationship between ploidy status and tGVBD, but tPB1 and the dMI were both significantly prolonged in eggs with reciprocal aneuploidy events compared to the euploid eggs, and this scaled with the severity of aneuploidy. Eggs with ≥4 aneuploid chromosomes had the longest tPB1 and dMI (P < 0.0001), whereas eggs with one to three aneuploid chromosomes exhibited intermediate lengths of time (P < 0.0001). N/A. We used Nocodazole in this study to disrupt the meiotic spindle and induce aneuploidy in mouse oocytes. Whether the association between morphokinetic variables of meiotic progression and the severity of aneuploidy occurs with other compounds that induce chromosome segregation errors remain to be investigated. In addition, unlike mouse oocytes, human IVM requires the presence of cumulus cells, which precludes visualization of morphokinetic variables of meiotic progression. Thus, our study may have limited direct clinical translatability. We validated NGS in mouse eggs to detect aneuploidy at a chromosome-specific resolution which greatly improves the utility of the mouse model. With a tractable and validated model system for characterizing meiotic aneuploidy, investigations into the molecular mechanisms and factors which may influence aneuploidy can be further elaborated. Time-lapse analyses of morphokinetic variables of meiotic progression may be a useful non-invasive predictor of aneuploidy severity. This work was supported by the Bill & Melinda Gates Foundation (INV-003385). Under the grant conditions of the Foundation, a Creative Commons Attribution 4.0 Generic License has already been assigned to the Author Accepted Manuscript version that might arise from this submission. The authors have no conflict of interest to disclose.

Clinical outcomes in carriers of insertional translocation: a retrospective analysis of comprehensive chromosome screening results

To evaluate the clinical outcomes in the carriers of insertional translocation (IT). Retrospective case series. University-affiliated reproductive medical center. Twenty-three couples with ITs. No direct interventions were involved; however, this study included patients who underwent preimplantation genetic testing for structural chromosomal rearrangements (PGT-SR). Outcome of preimplantation genetic testing for structural chromosomal rearrangements and percentage of blastocysts available for transfer. Among 23 IT carriers, 15 were simple interchromosome ITs (type A), 3 were intrachromosome IT carriers (type B), and 5 were interchromosome IT carriers combined with other translocations (type C). A total of 190 blastocysts from 30 cycles were biopsied, 187 embryos were tested successfully, and only 57 blastocysts (30.5%) from 21 patients were available for transfer (normal or balanced). The unbalanced rearrangement rate of type C was 79.2% (42/53), and the proportion of type A was 50.0% (57/114), which was significantly higher than that of type B (5%, 1/20). In type A, the probability of embryos harboring unbalanced rearrangement in female carriers was 56.0% (51/91), which was higher than that in male carriers (26.1%, 6/23). Furthermore, the haploid autosomal length value of the inserted fragment was correlated linearly with the incidence of abnormal embryos. In type A gametes, most gametes produced by 2:2 separation without crossover, and no 3:1 separation gamete was observed. The chance of identifying normal or balanced and mosaic blastocysts per mature oocytes in patients with ITs are 16.6% (67/404). Greater IT complexity results in fewer transferable embryos. For simple interchromosome ITs, female carriers and those with higher haploid autosomal length values have a higher risk of producing embryos with unbalanced rearrangement.

Comprehensive chromosomal screening for preimplantation genetic testing: A mini-review

Preimplantation genetic testing (PGT) consists of a group of genetic tests to evaluate preimplantation embryos before transfer to the uterus during in vitro fertilization (IVF). It effectively reduces the incidence of genetic defects at birth by preventing the transmission of inherited diseases to embryos. The use of PGT in IVF clinics has greatly improved clinical pregnancy outcomes for carriers of genetic abnormalities through the selection of embryos that are free from any genetic mutation/chromosomal anomalies. However, the accuracy of PGT in detecting aneuploidies and genetic mutations remains a point of contention due to the varied effectiveness of the techniques used. In recent years, a number of high-throughput assays have been developed to overcome the challenges associated with comprehensive chromosomal analysis. In this review, we will summaries the recent progress in using comprehensive chromosomal screening techniques, including array comparative genomic hybridization, single nucleotide polymorphism array, and next-generation sequencing, to evaluate chromosomal genetic defects.

Knowledge-embedded spatio-temporal analysis for euploidy embryos identification in couples with chromosomal rearrangements.

The goal of the assisted reproductive treatment is to transfer one euploid blastocyst and to help infertile women giving birth one healthy neonate. Some algorithms have been used to assess the ploidy status of embryos derived from couples with normal chromosome, who subjected to preimplantation genetic testing for aneuploidy (PGT-A) treatment. However, it is currently unknown whether artificial intelligence model can be used to assess the euploidy status of blastocyst derived from populations with chromosomal rearrangement. From February 2020 to May 2021, we collected the whole raw time-lapse videos at multiple focal planes from in vitro cultured embryos, the clinical information of couples, and the comprehensive chromosome screening results of those blastocysts that had received PGT treatment. Initially, we developed a novel deep learning model called the Attentive Multi-Focus Selection Network (AMSNet) to analyze time-lapse videos in real time and predict blastocyst formation. Building upon AMSNet, we integrated additional clinically predictive variables and created a second deep learning model, the Attentive Multi-Focus Video and Clinical Information Fusion Network (AMCFNet), to assess the euploidy status of embryos. The efficacy of the AMCFNet was further tested in embryos with parental chromosomal rearrangements. The receiver operating characteristic curve (ROC) was used to evaluate the superiority of the model. A total of 4112 embryos with complete time-lapse videos were enrolled for the blastocyst formation prediction task, and 1422 qualified blastocysts received PGT-A ( n = 589) or PGT for chromosomal structural rearrangement (PGT-SR, n = 833) were enrolled for the euploidy assessment task in this study. The AMSNet model using seven focal raw time-lapse videos has the best real-time accuracy. The real-time accuracy for AMSNet to predict blastocyst formation reached above 70% on the day 2 of embryo culture, and then increased to 80% on the day 4 of embryo culture. Combing with 4 clinical features of couples, the AUC of AMCFNet with 7 focal points increased to 0.729 in blastocysts derived from couples with chromosomal rearrangement. Integrating seven focal raw time-lapse images of embryos and parental clinical information, AMCFNet model have the capability of assessing euploidy status in blastocysts derived from couples with chromosomal rearrangement.

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.

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

PurposeTo 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.MethodsA 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.ResultsOf 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).ConclusionsCCS-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.

P-747 Chromosomal mosaic characteristics among women under IVF treatment: multicentric study of 2282 mosaic embryos diagnosed by preimplantation genetic testing with trophectoderm biopsy

Abstract Study question Which chromosomal mosaic features do women under IVF treatment show? Summary answer Single aneuploidies were the most represented among mosaic embryos and their frequency as well as the level of mosaicism increased in older women. What is known already Chromosomal mosaic embryos are characterised by the presence of chromosomally different cell lines within the same embryo. We previously demonstrated that reproductive potential of mosaic embryos is affected by the complexity of and the number of aneuploid cells present in trophectoderm (TE) biopsy. Although with the introduction of next generation sequencing (NGS) chromosomal constitution of human embryos have been elucidated, only limited number of mosaic have been characterised. Therefore, we performed a larger-scale multicenter study on mosaic embryos to examine the patterns and prevalence of chromosome specific mosaicisms in TE samples. Study design, size, duration This is a retrospective cohort study from May 2019 to May 2021 of 20200 embryos obtained from 5770 women under IVF treatment. From this cohort, 2280 mosaic embryos were analysed. All embryos were cultured to blastocyst stage; TE biopsy was performed on Day-5 of development or on Day-6/7 for slow growing embryos. Participants/materials, setting, methods TE biopsies underwent comprehensive chromosome screening (CCS) utilizing validated NGS. TE biopsies were classified as mosaic if they had 20%-80% of abnormal cells. For statistical analysis, embryos were divided in: single whole-chromosome trisomy, double whole-chromosome trisomies, single whole-chromosome monosomy, double whole-chromosome monosomies and complex aneuploidy (more than two different aneuploidies) groups. In addition, the frequency of single, double and complex segmental aneuploidies was evaluated. For each group, the trend related to maternal age was examined. Main results and the role of chance Among 2282 mosaic embryos single (whole-chromosome and segmental) aneuploidies were the most represented(52%) followed by complex(36%) and double ones(14%). When embryos were divided based on different types of aneuploidies, complex aneuploidies were the most frequent(34%) followed by segmental(31%), single monosomies(14%), single trisomy(12%). The more affected chromosomes within trisomies were 16(7%), 19 (7%), 21 and 22(6%). Monosomy involved mainly chromosomes 7(8%), 21 and 22(7%). Chromosomes 1, 5(9%), and 9(8%) were the most targeted by segmental duplication while segmental deletion mostly involved chromosomes 1(11%), 2(13%) and X(8%). The frequency of single aneuploidies as well as the percentage of mosaicism increased in older women. Limitations, reasons for caution This study was retrospective and observational, demonstrating the relative frequency of mosaicisms but not offering any direct insight into the clinical relevance of the findings. More clinical data must be obtained before this approach can be evaluated as an additional tool to choose mosaic embryos for the transfer. Wider implications of the findings This study provides a large dataset of mosaic embryos and offers detailed information on the distribution of different types of mosaicism among a general population of women under IVF treatment. Trial registration number Not applicable

P-721 Nanopore sequencing for detecting reciprocal translocation carrier status in preimplantation genetic testing

Abstract Study question Analyze the concordance between nanopore sequencing and MaReCs to validate the feasibility of nanopore sequencing in distinguishing normal embryos from carrier embryos in PGT-SR cycles. Summary answer Nanopore sequencing is a powerful strategy for accurately distinguishing nontranslocation embryos from translocation carrier embryos and precisely localizing translocation breakpoints. What is known already Balanced reciprocal translocation (BRT) is one of the most common chromosomal abnormalities that causes infertility, recurrent miscarriage, and birth defects. Preimplantation genetic testing (PGT) is widely used to select euploid embryos for BRT carriers to increase the chance of a healthy live birth. Several strategies can be used to distinguish reciprocal translocation carrier embryos from those with a normal karyotype; however, these techniques are time-consuming and difficult to implement in clinical laboratories. Study design, size, duration The Nanopore Sequencing was performed on two pregnant patients conducted on Mapping Allele with Resolved Carrier Status” (MaReCs) in PGT-SR cycles to identify translocation breakpoints for a year. Combined conventional MaReCs ’results, amniocentesis was performed to identify karyotypes at 18–20 weeks of gestation to verify the correctness of the Nanopore Sequencing. Participants/materials, setting, methods A total of 11 embryos from 2 couple1 and 12 embryos from couple 2 were tested simultaneously in PGT-SR cycles with a combination strategy of mate pair sequencing and PCR breakpoint analysis, SNP array-based comprehensive chromosome screening (CCS), NGS following micro-dissecting junction region (Micro-Seq) to distinguish between normal and carrier embryos. The Nanopore Sequencing based on TGS was performed on 2 couples. Lastly, amniocentesis was performed to test karyotypes. Main results and the role of chance The translocation breakpoints in both reciprocal translocation carriers were accurately identifed by nanopore sequencing and were in accordance with the results obtained using MaReCs. More than one euploid non-balanced translocation carrier embryo was identified in both patients. Amniocentesis results revealed normal karyotypes, consistent with the findings by MaReCs and nanopore sequencing. Limitations, reasons for caution One limitation is that it is not possible to identify the translocation breakpoints of Robertsonian translocation carriers or those located in the gap regions of the human genome. In addition, high-molecular-weight genomic DNA and large amounts of peripheral blood samples would be a challenge most PGT centers. Wider implications of the findings The nanopore sequencing accurately detects translocation breakpoints in BRT carriers and distinguishes translocation-free embryos from balanced diploid embryos in clinical PGT-SR cycles. It is superior to short reads (NGS) for the detection of translocation breakpoints, which shows broad prospects for clinical applications in blocking translocation propagation in the population. Trial registration number Not applicable

O-077 Time-lapse imaging analysis of segmental aneuploid embryos: a multicenter study identifies morpho-kinetic patterns associated with chromosomal mosaicism

Abstract Study question Do segmental aneuploid (SA) embryos display unique morpho-kinetic patterns at early developmental stages? Summary answer The first three cell division cycles of embryos carrying segmental aneuploidies are significantly slower than euploid and whole-chromosome aneuploid (WCA) embryos. What is known already Segmental aneuploidies in blastocyst-stage human embryos prevalently originate (i.e., 70% of cases) from mitotic errors. Their clinical management is challenging because it is impossible to establish their meiotic/mitotic origin from PGT-A analysis of a single trophectoderm biopsy. Morpho-kinetic analysis based on Time-lapse microscopy (TLM) has been proposed as a valuable tool for systematic embryo evaluation, although it is unclear whether this approach alone can predict chromosomal abnormalities. This study aims to pinpoint morphokinetic patterns associated with the occurrence of segmental aneuploidies and/or mitotic errors, possibly improving DNA-based diagnostic interpretation and their clinical management. Study design, size, duration This is a retrospective multicenter study including a total of 7,693 embryos from 2,370 IVF cycles and 2,127 couples, cultured between 2016 and 2021 in 4 European IVF centers. Embryos with no more than 4 chromosomal alterations were considered in the analysis, resulting in 3,288 euploids, 3,155 WCA, 715 SA, and 535 complex aneuploids (CA). Overall, the dataset contained 3,742 distinct euploid-SA embryo sibling pairs. Participants/materials, setting, methods Standard morpho-kinetic features were annotated using various TLM systems. Blastocysts were subjected to comprehensive chromosomal screening via PGT-A. Morpho-kinetic timings across different embryo groups were compared using Kolmogorov-Smirnov (KS) test and binomial test, and associations with cleavage features were assessed via two-sided Fisher Exact (FS) test. Multi-center and center-specific logistic regression models were calibrated using a subset of data (70%), and their predictive performance was evaluated on independent test data using Area-Under-ROC curve (AUROC) metrics. Main results and the role of chance SA embryos cleaved at significantly slower rate than their euploid siblings in the first 3 cell cycles, from the appearance of the second blastomere t2 (average delay delta=0.49h, KS p = 0.006, fraction of pairs in which SA was delayed compared to euploid sibling F = 54.2%, binomial p = 0.002) up to t8 (delta=2.16h, KS p = 4e-4, F = 57.9%, binomial p = 1e-8). The developmental delay was partially compensated at full blastocyst stage tB (delta=1.71h, KS = 0.0008, F = 57.5%, binomial p = 5e-8). SA timings also differed from WCA ones: SA embryos were significantly slower than their WCA siblings during early cell cycles, with maximum delay reached at t8 (delta=1.67h, KS p = 0.009, F = 55.4%, binomial p = 0.003), but they fully caught-up at tB, with no significant difference observed. These morpho-kinetic patterns were consistently observed in each center separately, but with different effect sizes. The presence of segmental aneuploidies was significantly associated with multinucleation (OR = 1.99, FS test p = 0.05) and morula cell exclusion (OR = 2.69, p = 0.006). A logistic model based on morpho-kinetic data and cleavage features from a single center dataset and regressed against embryo aneuploidy class (euploid vs. SA embryos) displayed adequate predictive performance on independent data from the same center (AUROC=0.70), although predictivity diminished when tested on data from other centers (AUROC=0.52-0.55). Limitations, reasons for caution We cannot rule out inter-center variability in the annotation procedures of morpho-kinetic parameters. Standardized and automated annotation would increase the performance of predictive models and their transferability. Further work is needed to assess whether the morpho-kinetic signal is driven by mitotic errors and if an association with clinical outcomes exists. Wider implications of the findings These findings might help uncovering biological events contributing to preimplantation mosaicism. Moreover, the developed predictive framework might help improving decision-making in PGT-A cycles, providing interpretation for segmental aneuploidies and possibly helping in the evaluation of embryos showing intermediate copy number values for whole chromosomes that are suggestive of mosaicism. Trial registration number Not applicable

The Fischer protocol for assisted reproductive technology treatment: Real-world data experience comparing elective single versus double embryo transfer with or without comprehensive chromosome screening.

High rates of multiple implantation after assisted reproductive technology (ART) treatment represent one of the major problems for both mothers and their fetuses. Given the availability of techniques intended to identify embryos with the highest chance for development to term, such as comprehensive chromosome screening (CCS) and blastocyst transfer, the decision on the number of embryos to transfer deserves careful consideration. This report presents real-life data from two clinics using the Fischer protocol for cycle programming in patients undergoing ART. Our data indicate that ovarian stimulation using the Fischer protocol provides consistent and optimal ART outcomes in centers following strict quality management standards. However, high multiple implantation rates were observed in fresh and frozen transfer cycles after transferring two embryos - even in patients aged over 39 years. The live birth rates after CCS were superior to those using untested embryos. These findings were held for the three age groups irrespective of the CCS culture day (D1=PN stages, or D5=blastocysts). Our results support a single embryo transfer policy, particularly in women under 34 years of age with favorable conditions during ART treatment, i.e., a high number of available fertilized oocytes.

Preimplantation Genetic Testing for Aneuploidy with Comprehensive Chromosome Screening in Patients Undergoing In Vitro Fertilization: A Systematic Review and Meta-analysis.

Next Fertility IVF Prof. Zech, Bregenz, Austria Next Fertility IVF Prof. Zech, Salzburg, Austria Financial Disclosure The authors did not report any potential conflicts of interest.

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

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. 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. 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. 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.

Preimplantation Genetic Testing for Aneuploidy With Comprehensive Chromosome Screening in Patients Undergoing In Vitro Fertilization: A Systematic Review and Meta-analysis.

To review the effect of comprehensive chromosome screening-based preimplantation genetic testing for aneuploidy (PGT-A) in women undergoing in vitro fertilization (IVF) treatment, we conducted this meta-analysis to compare pregnancy outcomes of women who did and did not undergo such testing. We searched Medline, EMBASE, the Cochrane Central Register of Controlled Trials, and ClinicalTrials.gov from their inception until February 28, 2022, for randomized controlled trials focusing on PGT-A treatment without any language restrictions. Randomized controlled trials involving women undergoing IVF with or without PGT-A and comprehensive chromosome testing. Pooled relative risks (RRs) with 95% CIs were calculated for the primary outcome using a random-effects model with the Mantel-Haenszel method. A total of nine trials with 3,334 participants were included. Overall, PGT-A was not associated with an increased live-birth rate (RR 1.13, 95% CI 0.96-1.34, I 2 =79%). However, PGT-A raised the live-birth rate in women of advanced maternal age (RR 1.34, 95% CI 1.02-1.77, I 2 =50%) but not in women of nonadvanced age (RR 0.94, 95% CI 0.89-0.99, I 2 =0%). Preimplantation genetic testing for aneuploidy increases the live-birth rate in women of advanced maternal age. PROSPERO, CRD42022311540.

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.