Aneuploidy Rate Research Articles

P-696 Identification of novel candidate genes associated with meitotic aneuploidy in human embryos by whole-exome sequencing (WES)

Abstract Study question Can certain genetic variants in women cause a genetic predisposition to aneuploidy? Summary answer Our results suggest that the maternal variants identified in genes regulating meiotic processes could be useful genetic biomarkers for predicting a predisposition to embryonic aneuploidies. What is known already Errors in chromosome segregation during meiosis as chromosome synapsis, crossing-over and spindle building, occur frequently in human oocytes and cause aneuploidy in embryos. These errors increase dramatically in the oocytes of older women. However, the rate of producing aneuploidy oocytes varies among IVF patients for a given age. Recent publications have identified genetic variants that are crucial for producing healthy oocytes in female IVF patients. The association between maternal genetic variants and embryonic aneuploidy risk suggests the potential of using genomic data to predict embryonic aneuploidy risk. Our aim was to identify novel variants and candidate genes for embryonic aneuploidy. Study design, size, duration A prospective observational cohort study was done including 127 trophoectoderm biopsies from 29 couples who performed whole-exome sequencing (WES) and PGT-A between November 2019 and March 2022. Women were 35 years old or younger and normal karyotype for men and women. Patients were divided in two groups according to the embryo aneuploidy rate expected by their maternal age: ≤ 50% of aneuploid blastocysts as control group(n = 14), and ≥ 50% of aneuploid blastocysts as study group(n = 15). Participants/materials, setting, methods WES was performed using Trusight One Expanded Sequencing Panel (Illumina®). The following criteria were used for filtering and annotation of candidate variants: (1) minor allele frequency (MAF) <0.05 in the gnomAD and 1000 genomes, (2) variants in genes previously associated with chromosome segregation, chromatin cohesion, meiosis and cell division processes, (3) exonic/splicing boundaries variants, (4) variants having potentially strong/moderate functional effects on the protein evaluated using three in silico prediction algorithms (SIFT, PolyPhen-2 and MutationTaster). Main results and the role of chance Overall, the mean female and male age was 26.21 + 4.11y and 40.69 + 9.07y respectively. No differences were shown between groups for patient characteristics. Regarding PGT-A cycle no differences were seen between the number of oocytes and MII retrieved. However, the mean number of biopsied embryos per patient (5.36 + 2.50 vs 3.47 + 1.36; p < 0.05) as well as the percentage of embryos biopsied on day 5 (85.33 vs 32.69; p < 0.05) were higher in the control group. Finally, as expected, the percentage of aneuploidies was higher in the study group (18.64 vs 71.89; p < 0.05). 45 variants were identified in genes potentially associated to the mechanism related to the phenotype. After the variant filtering six probably pathogenic variants were identified. The variants found in the genes were: c.1397T>C (TLE6), c.169G>A (IKBKG), c.1227A>C (BUB1B), c.277G>A (TP73), c.190C>T (PLXNA3) and c.744C>G (AURKC). All variants were heterozygous and all of them were of maternal origin. The females carrying the candidate variants belonged to the study group, and two variants in different genes were identified in one patient. No potentially pathogenic variants were detected in patients from the control group. Therefore, the average detection rate of genetic variants with potential impact in embryo aneuploidy was 33.33% (5/15). Limitations, reasons for caution A notable strength of our study is the inclusion of both (male and female) genomic data. On the other hand, our study has certain limitations including the inherent challenges of any observational study, also, the pathogenicity of the identified variants should be validated in further functional studies. Wider implications of the findings We described new candidate genes that have never been associated to meiotic embryo aneuploidy and are involved in important biological processes (cell division and chromosome segregation). WES may be considered as an efficient tool to identify patients with higher risk of embryo aneuploidy allowing an individualized genetic counselling in advance. Trial registration number Not applicable

P-242 Genetic laboratories report significantly different aneuploidy rates for identical patient populations, a finding with important implications for clinics using PGT-A

Abstract Study question If a clinic changes the genetic laboratory it works with, should it expect its new PGT-A results to be equivalent to those it received previously? Summary answer Changing the genetic service provider can result in a significant difference in the proportion of embryos classified euploid, with important clinical implications. What is known already Preimplantation genetic testing for aneuploidy (PGT-A) aims to distinguish potentially viable euploid embryos from embryos harbouring lethal chromosome abnormalities. Typically, IVF clinics perform biopsy at the blastocyst stage and send the resulting trophectoderm specimens to specialist genetic laboratories for analysis. However, many commercially available genetic methods have not been subjected to rigorous validation, leading to uncertainty about their accuracy and predictive value. It would be concerning if the classification of embryos, derived from the same patient population, and from the same clinic, varied depending on the company that provides PGT-A services. Such differences would be unlikely to reflect biological reality. Study design, size, duration Our clinic recently began working with a new genetics company. Our previous PGT-A reference laboratory issued results for 1,136 blastocyst biopsy specimens over ∼15 months. Subsequently, the second company tested 784 biopsy samples in 7 months. Patient populations during the two periods were essentially identical (average maternal age 38.0 years). Participants/materials, setting, methods The first company used whole genome amplification followed by next generation sequencing (NGS) to evaluate the relative amount of DNA from each chromosome. The second company’s method was highly validated, involving targeted amplification of thousands of sites in the genome, again followed by NGS and analysis of relative DNA quantity from individual chromosomes. Additionally, they genotyped numerous polymorphisms, which assist in the detection of haploidy/triploidy, and also reveals problems that can compromise accuracy (e.g. contamination). Main results and the role of chance The first PGT-A company classified 44.4% of blastocysts euploid, 4.1% low-level mosaic, 51.5% aneuploid. In contrast, the second company reported significantly fewer embryos aneuploid (44.0%; P = 0.0019). Even if the mosaics reported by the first company are considered for transfer, the second company is still associated with more potentially transferable embryos (relative increase greater than one-sixth). If PGT-A results from the second company are correct, it implies that potentially viable embryos may have been misclassified by the first company, risking their exclusion and loss of the pregnancies they might have produced. Conversely, if the first company is correct, the second company may be failing to detect some aneuploidies, leading to inadvertent transfer of abnormal embryos, lower pregnancy rates and a higher incidence of miscarriage. 299 transfers following PGT-A using the first company produced 171 pregnancies (74.7%), while 64 single embryo transfers have taken place after PGT-A with the second company, resulting in 53 pregnancies (82.8% per transfer). Losses (biochemical or miscarriage) affected 21.6% and 16.9% of pregnancies after PGT-A conducted by the first and second companies, respectively (ongoing pregnancy rates of 58.5% and 68.8% per transfer, respectively) Thus, there is no evidence that aneuploidies are being missed by the second company. Limitations, reasons for caution Although there were no obvious differences between the patients with embryos tested by the two companies, this study was not prospective nor randomized, so a possibility of undetected differences remains. The study was not sufficiently powered to test the significance of apparent differences in implantation, miscarriage and ongoing pregnancy rates. Wider implications of the findings It is important that IVF clinics appreciate that individual PGT-A methods differ significantly, and that some have undergone much more rigorous validation than others. It is recommended that clinics ask PGT providers to share their validation data, especially clinical studies confirming that embryos classified ‘aneuploid’ or ‘abnormal’ are truly non-viable. Trial registration number Not applicable

P-261 Embryo compaction based on time-lapse imaging is a valuable parameter for selecting blastocysts with the highest developmental potency and associated with a ploidy state

Abstract Study question Does embryo compaction positively correlate with blastocyst development and further embryonic ploidy status? Summary answer Fully compacted embryos develop into good-quality blastocysts, have shorter developmental times, and are related to ploidy status. What is known already To succeed in assisted reproduction technique (ART), it is necessary to select embryos that have the highest potential. So, numerous studies make an effort to establish parameters for selecting embryos. A Time-lapse system (TLS) allows embryologists to understand dynamic embryo change through continuous monitoring. In development, embryos undergo dynamic functional changes during compaction, which play a crucial role in blastocyst formation. It is also known that embryonic genome activation can be seen with compaction. Incomplete compaction leads to blastocyst developmental failure. Nevertheless, the details about the compaction of human embryos have not been paid sufficient attention, so still rarely known. Study design, size, duration This was a retrospective cohort study including couples that underwent an IVF cycle at the CHA Fertility Center, Gangnam, between January 2019 to October 2022. A total of 371 reached the blastocyst from 113 patients cultured in the TLS were analyzed. Among these, 94 blastocysts were analyzed by preimplantation genetic testing for aneuploidy (PGT-A). Statistical analysis was performed by prism9 using a t-test and chi-square test. P values <0.05 were regarded as statistically significant. Participants/materials, setting, methods Embryos were classified into two categories by compaction pattern: fully compacted (Group1, N = 194) and partially compacted (Group2, N = 177). Blastocyst quality was determined by morphology and divided into three groups (Good, Average, and Poor). The developmental time ranging from morula to blastocyst was annotated based on the embryo scope image. The surface of the blastocyst was measured every hour starting at blastocyst formation (tB) by using the ellipse tool of the Embryo Viewer software. Main results and the role of chance Good and average quality blastocysts are significantly higher in Group 1 than in Group 2 (21.6% vs. 3.4%, p < 0.01; 47.9% vs. 26.6%, p < 0.01, respectively). In contrast, poor-quality blastocysts are lower in Group 1 than in Group 2 (30.4% vs. 70.1%, p < 0.01). The beginning and completion of compaction, and blastocyst formation times of embryos from Group 1 were significantly shorter than those of embryos that Group 2(78.6h vs. 82.4, p < 0.01; 87.0h vs. 92.2h, p < 0.01; 100.2h vs. 103.7, p < 0.01, respectively). Also, there is a significant difference in longitudinal surface area at 3, 6, and 12h from the time of tB between the two groups. Consequently, the average expansion rate in Group 1 was significantly faster than in Group 2 (653.6 μm2/hour vs. 499.2μm2/hour, p < 0.05). According to the result of PGT-A, Group 1 had statistically significantly higher euploid and lower aneuploidy rates compared to Group 2 (47.2% vs. 36.2%, p < 0.001; 52.8% vs. 63.8%, p < 0.001, respectively). However, in the PGT-A group, there was no significant difference in developmental time between the two groups, regardless of fully or partial compaction. Meanwhile, the average expansion rate in euploidy blastocyst was significantly faster than in aneuploidy blastocyst (747.8 μm2/hour vs. 564.3 μm2/hour, p < 0.05). Limitations, reasons for caution The main limitation is the single-center retrospective approach. Therefore future prospective research is needed to verify and extend our findings. Another one, in the PGT-A there was no difference in developmental time regardless of fully or partially compaction. The reason is that we selected blastocysts of sufficient quality for biopsy. Wider implications of the findings Using the TLS, we have observed the dynamics of compaction in detail. We found a positive relationship between compaction and blastocyst quality and its association with embryo ploidy. The assessment of compaction is a significant parameter for predicting competent embryos and should be given priority when selecting blastocysts. Trial registration number Not applicable

P-255 Increased time in thawing solution improves human oocyte warming outcomes

Abstract Study question Can increased time in thaw solution improve oocyte survival and outcomes following vitrification/warming? Summary answer Exposing vitrified oocytes to the first step thawing solution for 90 seconds improved oocyte survival compared to 60 second exposure. What is known already Oocytes are a sensitive cell type and careful handling of the cells is required to obtain high outcomes following vitrification and warming. Carefully timed exposure to various vitrification solutions is required to avoid toxicity and ensure proper vitification. Similarly, proper and carefully timed exposure to warming solutions is required to avoid oocyte damage upon warming. Recent reports suggest a modified and rapid warming protocol may be beneficial for vitrified blastocysts. However, oocytes are unique cells and may require unique considerations to optimize warming. Study design, size, duration Retrospective analysis of donor oocyte warming outcome data within a single IVF lab over a 12 month period comparing a 60 second first step during oocyte warming (control n = 637 oocytes) versus a very consistent 90 second exposure (n = 672 oocytes) to the first step thawing solution. Participants/materials, setting, methods Human donor oocytes were vitrified using the standard Kitazato protocol with ES drop merging and loading on CryoTop devices using the wicking method prior to plunging into liquid nitrogen. Warming was performed using the standard protocol of 60 seconds in thaw solution (TS) or 90 seconds exposure. All cycles utilized ICSI and excluded testicular sperm samples. Survival, fertilization and blastocyst development were compared between the two exposure groups. Data were analyzed utilizing Fisher’s Exact Test. Main results and the role of chance Oocyte survival differed between the two timing treatments, with exposure to TS for 90 seconds yielding higher oocyte survival (96.1%) than 60 secondsTS exposure (92.0%), p < 0.002. No differences in fertilization following ICSI (78.3.0% vs. 79.0%) orin good quality blastocyst conversion (≥3BB) on day 5 (22.1% vs. 25.1%) or by day 7 (55.3% vs. 55.7%) were apparent. The aneuploidy rate of blastocysts were similar, with 28.5% in the 90 second TS treatment group and 27.3% in the 60 second TS exposure group. Limitations, reasons for caution Data were examined retrospectively and sibling oocyte splits were not utilized. Clinical outcomes following resulting embryo transfer were not examined. Wider implications of the findings These data may help improve oocyte warming protocols and resulting outcomes. Trial registration number not applicable

O-091 The impact of endocrine disruptors on early pregnancy and clinical outcomes in IVF

Abstract The impact of endocrine disruptors on early pregnancy and clinical outcomes in IVF Moncef Benkhalifa (1,2,3), Debbie Montjean (2), Hafida Corsi-Cauet (3), Henri Copin (1,3), Véronique Bach (3), Pierre Miron (2), Rosalie Cabry (1,3) (1) Reproductive Medicine and Reproductive Genetics, University Hospital & School of Medicine. Picardie University Jules Verne. Amiens France (2) ART Centers. Laval and Brossard. Fertilys International Inc. Laval. Québec. Canada (3) PERITOX Laboratory. Picardie University Jules Verne. Amiens. France Since more than 40 years, there are annual increasing of studies, meta-analysis reporting and discussing the potential associations between endocrine disrupting chemicals (EDCs) and human fertility potential declining. Today it’s accepted that a substantial number of environmental and exposition factors affect the fertility and fecundity capacity of couples during the peri and post conception period. It’s accepted that most of EDCs interfere with or mimic steroid hormone action; predominantly by affecting estrogen, androgen and thyroid hormones signaling pathways and disturbing specific molecular process on relation with single or multiple biological functions. Some of EDCs can interact with the male and female reproductive system and lead to endocrine disruption in the testis and ovary. they exert their effects mainly via binding transcription factor receptors, EDCs can alter endocrine function through a variety of mechanisms. At fertility age EDCs may alter the expression and/or activity of enzymes required for synthesis and/or catabolism of testicular and ovarian sex steroids and the expression of hormone receptors and/or their ability to bind their and endogenous ligands. For example, in male, the literature reported a negative correlation between disrupted spermatogenesis and lifestyle factors (environmental-professional expositions) such as alcohol consumption, cigarette smoking, drug use, and obesity caused by high-energy diet. In female infertility diseases, the negative impact of chemicals ED has been studied in animals. Many disorders have been described, such as low ovarian weight, impaired folliculogenesis, a high aneuploidy rate and the acceleration of follicular atresia. Indeed, women exposed to some endocrine-disrupting pesticides (such as atrazine, lindane) have an elevated risk of long menstrual cycles or anovulation but the most serious consequence is POF and endometriosis pathophysiology’s. In our IVF experience in Picardie region (France), we observed that various pesticides with an endocrine-disrupting action are associated with poor oocyte quality (maturation and competency), embryonic defects and poor IVF outcomes, and some pesticide compounds are linked to specific causes of female infertility, such as premature ovarian insufficiency, polycystic ovarian syndrome, and endometriosis. It was reported that EDCs can reduce embryo implantation chances and increase miscarriage, placenta and post-natal abnormalities. for endometrium receptivity and implantation failure EDCs can play by modifying keys elements of the immune response relevant to pregnancy, and disrupt immune tolerance required for robust placentation, optimal fetal development and be a as contributing risk factors in recurrent miscarriage, preeclampsia, preterm birth and related pathologic gestation Environmental insults, including endocrine disrupting chemicals during critical periods of fetal development, can alter DNA methylation patterns, leading to inappropriate developmental gene expression and disease risks. Similar to environmental factors, endocrine-disrupting chemicals can influence gene expression without modifying the DNA sequence. It is commonly accepted that the transgenerational inheritance of parentally acquired traits is conveyed by epigenetic alterations risks also known as “epimutations”. In Conclusion, the negative impact of exposure to various endocrine-disrupting is becoming now a worldwide public health. Indeed, the community should be informed about the fertility decline, low ongoing pregnancy rates, and elevated risk of miscarriage associated with exposure to high doses of pesticides for example. We must keep in mind that humans are exposed to EDCs mixtures composed of hundreds of chemicals every day and not a single chemical in isolation.

O-205 Poor mitochondrial metabolism impairs meiosis and contributes to reduced oocyte maturation rates in patients with advanced maternal age

Abstract Study question Is there a relationship between poor mitochondrial metabolism and impaired meiotic progression of germinal vesicle (GVs) oocytes in women of advanced maternal age (AMA)? Summary answer Poor mitochondrial metabolism impairs meiotic progression in human oocytes, contributing to a lower oocyte maturation capacity in women of AMA. What is known already High aneuploidy rates and impaired metabolism are characteristic features of AMA oocytes. Studies in mouse suggest that successful meiotic maturation and metabolic competency may be functionally linked, however this relationship has not been clearly established in human. Metabolic dynamics can be visualized by indirect measurements through mitochondrial staining and quantified more directly using Fluorescence Lifetime Imaging Microscopy (FLIM). This live-imaging approach can generate metabolic timelapse profiles of oocytes throughout meiosis. We performed an extensive characterization of oocyte metabolism in maturing GVs, obtained from both young and AMA patients, to establish the importance of mitochondrial metabolism during meiosis. Study design, size, duration A total of 401 GVs from young (≤30 years, n = 264) and AMA (>37 years, n = 137) women were included in the study. GVs were matured in vitro in G2-plus medium for 30 hours. Maturation was determined by the presence of an extruded polar body. Oocytes were used for FLIM (n = 175) and immunofluorescence (IF) analysis (n = 226). Further, mitochondrial metabolism loss of function studies (n = 64) were performed by treating young GVs with 1μM Trifluoromethoxy-carbonylcyanide-phenylhydrazone (FCCP) for 30 minutes. Participants/materials, setting, methods The proteins Dihydrolipoamide-S-Acetyltransferase (D-LAT) and Translocase-of-outer mitochondrial-membrane (TOMM20) were analysed in young and AMA oocytes by IF (Arbitrary-Unit, AU) to assess mitochondrial activity and localization, respectively. Fluorescence mean intensities were quantified with ImageJ and compared by t-test; maturation rates were compared by Chi-squared test. FLIM comprehensive metabolism (NADH; FAD+) were taken at GV stage. Different FLIM parameters (fluorescence intensity, fraction bound, short/long lifetime) were evaluated individually and combined into the Redox ratio (NADH intensity/FAD+ intensity). Main results and the role of chance Mitochondrial staining showed a common pattern in young and AMA GV oocytes, with a uniform localization of mitochondria in the ooplasm (TOMM20) and a subcortical localization of active organelles (D-LAT). These patterns were confirmed by in-live FLIM analysis. The total mitochondria abundance was comparable between AMA and young GV oocytes (intensity of 61674±24322 AU in young, 32186±33414 AU in AMA, p = 0.195), however, active mitochondria were diminished in AMA compared to young GVs both by IF and FLIM (intensity of 78614±58534 AU in young, 12517±10187 AU in AMA, p = 0.003; Redox ratio in young 2e+00±0.15, in AMA 1e+00 ± 0.16, p = 2.969e-05). Notably, young oocytes matured at a significantly higher rate (86.3%; 63/73) than AMA oocytes (62.3%; 38/61; p = 0.002). Moreover, FLIM imaging revealed that GVs with a higher metabolism were more likely to complete meiosis to MII (Redox ratio 2e+00±0.17 in GVs matured to MII, 1e+00±0.18 in non-matured, p = 1.054e-06). Following treatment with FCCP, young GVs showed a similar phenotype to AMA oocytes, with a significant decrease in mitochondrial activity (intensity of 78614±58534 IU in untreated and 11554±16131 IU in treated GVs, p = 0.019), and an associated drop-in maturation rate. Ultimately, only 39.5% (17/43) of the young treated GVs were able to accomplish meiotic maturation. Limitations, reasons for caution Maturation rates were assessed by the presence of an extruded PB and variations in spindle assembly timings may have been overlooked. The quantification of mitochondrial activity in loss of function studies was assessed only by IF staining. Wider implications of the findings Our findings demonstrate the presence of a functional link between oocyte metabolism and impaired meiosis, which may contribute to the decline of oocyte quality with age. Given that live-metabolic imaging is able to discern GVs that progress through meiosis, this approach may represent a valuable non-invasive tool in oocyte selection. Trial registration number not applicable

O-290 Clinical utility of putative mosaicism detected using concurrent copy-number and genotyping PGT method: outcomes from multisite, prospective, non-selection study including 9828 single embryo transfer cycles

Abstract Study question What is the clinical utility and associated outcomes of mosaic whole chromosome or segmental aneuploidies detected using concurrent copy-number and genotyping analysis in PGT-A cycles? Summary answer Although high-level whole-chromosome mosaicism is linked to reduced sustained implantation, it has limited clinical significance in PGT-A cycles when co-evaluated with other clinical/ embryological factors What is known already NGS-based PGT-A can detect intermediate chromosomal copy number (CN), commonly interpreted as mosaic chromosomal aneuploidies in embryos. A prospective non-selection approach is the most effective way to assess the clinical utility of reporting putative mosaicism findings in PGT-A, wherein the presence of mosaicism is not disclosed and does not influence embryo selection. Conflicting results have been reported previously, possibly due to technological limitations in mosaicism assessment or retrospective analysis methods. This study reports the results of the largest multisite prospective non-selection clinical study examining the predictive value of whole-chromosome and segmental mosaicism, assessed through combined CN and genotyping data analysis. Study design, size, duration A multisite study involving seven IVF clinics was conducted from Feb 2020 to Oct 2022, including 6951 patients and 9828 single embryo transfers. The study involved a prospective non-selection approach, where embryos suspected of having whole chromosomal or segmental mosaicism were reported as negative for non-mosaic aneuploidies. Embryos were chosen for transfer based solely on standard morphological features. The primary outcome was sustained implantation rate (SIR) defined as pregnancy continuing beyond 8 weeks of gestation. Participants/materials, setting, methods In this study, the trophectoderm biopsies were analyzed using a custom, targeted NGS assay that examined approximately 5000 loci across the genome, providing genotyping information to support aneuploidy classification. Mosaicism was identified by any copy number deviation from the expected two copies (LogR plots) and confirmed by corresponding SNP B-allele frequency (BAF) patterns. Confounding factors, such as clinical and embryological variables, were controlled for in the multivariate analysis. Main results and the role of chance The average female age in this cohort was 34.9 years (SD = 4.1), with aneuploidy rate of 30% in embryos and SIR of 61.2%. Of the embryos transferred, 6.5% (636/9828) were whole chromosomal mosaic (WCM) only; 9.6% (947/9828) were segmental mosaic (SM) only and 1% (83/9829) were a combination of WCM and SM. The rate of putative mosaicism ranged from 15%-89%. The SIR of embryos in the control group (non-mosaic), SM and WCM were 62% (5190/8328; 95%CI), 58% (549/947;95%CI) and 50.3% (320/636; 95%CI P < 0.01) respectively. A logistic model found that the level of WCM was associated to SIR, along with other embryological and clinical factors. In particular, WCM with a CN difference >50% as well as poor embryo morphology were associated with lower SIR (OR = 0.5; 95% CI:0.32-0.76), but low-level (<50%) mosaicism was not significant (NS). Notably, female age (OR = 0.98; 95% CI:0.97-0.99 per year), BMI (0.98; 95% CI:0.98-0.99) and previous ET failures (OR = 0.58; 95% CI:0.5-0.68) were strongly associated with SIR. A predictive model, taking into account all relevant variables, yielded a significant stratification of SIR, from 43% to 68%. Given the low incidence of WCM in our clinical setting, the multivariate SIR prediction (AUC) was 0.580 without WCM and 0.585 with mosaicism included. Limitations, reasons for caution This study did not have prenatal and post-natal data available at the time of the abstract's writing, hence conclusions about these outcomes wasn’t possible. Despite the large sample size, chromosome specific analysis was not feasible. Furthermore, this study’s data is platform-specific and cannot be translated to other PGT-A assays. Wider implications of the findings In this non-selection study, WCM of > 50% variation was associated with lower SIR. However, high-level WCM has a minimal overall impact on SIR when co-evaluating with other clinical/ embryological parameters. Decisions on reporting criteria for these findings must weigh the risk of discarding potentially viable embryos with substantial reproductive potential. Trial registration number Not applicable

O-064 Genome-wide analysis of meiotic recombination reveals a subset of oocytes with reduced frequency of recombination and increased risk of aneuploidy.

Abstract Study question Are there differences in recombination rates between male and female embryos, and is the frequency of recombination associated with the risk of aneuploidy? Summary answer There is more recombination in female meiosis than in males. Aneuploidy is associated with fewer recombination events. Genome-wide reduction in recombination predisposes oocytes to aneuploidy. What is known already Aneuploidy is believed to be the primary explanation for embryo implantation failure and miscarriage and is, therefore, of great relevance to IVF. Despite the high frequency and clinical importance of aneuploidy, the mechanisms causing a gamete to become chromosomally abnormal are only partially understood. One factor known to influence the risk of aneuploidy is meiotic recombination. An absence of recombination or atypical positioning of chiasmata predisposes to chromosomal malsegregation. Most data on the subject of meiotic recombination and aneuploidy comes from miscarriages and aneuploid births, but this provides an incomplete view since most aneuploidies are lethal at earlier developmental stages. Study design, size, duration ∼300,000 polymorphisms scattered across the genome were genotyped in DNA from 125 couples and 543 blastocysts that they produced. The inheritance of individual alleles was tracked from parents to embryos, allowing the parental origin of each chromosome to be determined. This strategy also permitted the detection of abnormal numbers of chromosomes, allowed deduction of which meiotic division aneuploidy had arisen in, and revealed the sites of meiotic recombination on each chromosome in the embryos analysed. Participants/materials, setting, methods Embryo analysis involved trophectoderm biopsy, followed by multiple displacement amplification. Parental DNA and amplified embryo samples were then tested using a microarray. 22,133 individual recombination events on 14,561 chromatids were evaluated. The relationship between aneuploidy and recombination frequency was considered. The average distance between recombination events was calculated by dividing the size of each autosome (in Mega bases – Mb) by the number of detected recombination events. An unpaired t-test was conducted for statistical analysis. Main results and the role of chance A quarter of all embryos were found to carry one or more chromosome abnormalities (altogether, 221 chromosome abnormalities were detected). Of these, 82% had a maternal (oocyte) origin, while 18% were paternal. Chromosomes 16 and 22 were the most frequently affected by aneuploidy, together accounting for 33% of all maternal chromosome abnormalities. Analysis of recombination events in maternally and paternally inherited chromosomes confirmed that female meiosis is associated with a significantly higher frequency of recombination (41.4 ±7.7 recombination events compared with 24.4±4 in chromosomes of paternal origin). Chromosomes 21 and 22 showed the lowest number of recombination events, consistent with their small size (average of 0.6 and 0.7 recombination sites per chromosome, respectively). As expected, a complete failure of recombination occurred more frequently for chromosomes with lower numbers of recombination events. Interestingly, embryos with aneuploidies of maternal origin showed evidence that the oocytes that produced them had lower recombination rates in general (not restricted to the affected chromosomes) than those producing euploid embryos (P = 0.01). Across the genome, average distances between recombination events were ∼10% lower for euploid embryos compared with aneuploid embryos (72.4 +/-14 Mb versus 81+-18 Mb) (P = 0.0004). Limitations, reasons for caution It is possible that the pattern and frequency of recombination sites that exist in sperm and oocytes might show some differences from the blastocysts tested during this study, considering that more than half of all oocytes either fail to fertilise or produce embryos that arrest before the blastocyst stage. Wider implications of the findings As expected, a higher aneuploidy rate and more recombination events were seen in female meiosis compared with male meiosis. Interestingly, aneuploidy was associated with lower levels of recombination across the whole genome, not only for the affected chromosomes, suggesting that unusually low recombination activity predisposes some oocytes to chromosome malsegregation. Trial registration number not applicable

P-717 Segmental aneuploidies are not related to paternal age in young women

Abstract Study question Is there an impact of paternal age on embryo segmental aneuploidy rate? Summary answer Even when segmental aneuploidies are most linked to paternal origin, results do not show a relationship between paternal age and embryo segmental aneuploidies. What is known already Most studies consider maternal age as a risk factor for spontaneous abortion, infertility and genetic defects in the offspring. However, attention has only recently turned to the impact of paternal age on reproductive outcome. In Assisted Reproduction Technology male age has been related to a decrease in sperm quality and clinical outcomes and an increase in sperm DNA damage has been identified among elderly males. Studies assessing the type of chromosomal aneuploidy associated with paternal aging have reported mixed relative risk results for chromosomes 13, 18, 21, and X. Segmental aneuploidies are most linked to paternal origin. Study design, size, duration Observational, retrospective and multicentric study. The study was approved by the local institutional review board (IRB). All the patients underwent an IVF cycle with oocytes from egg donors, followed by Preimplantation Genetic Testing for Aneuploidy (PGT-A) at IVI-RMA Madrid, IVI-RMA Valencia and IVI-RMA Barcelona from January 2018 to August 2022. A total of 3412 biopsied embryos obtained from 660 cycles were included in the study. Participants/materials, setting, methods Exclusion criteria were the following: altered karyotype, single gene disorder and male factor (sperm concentration lower than 5 million/ ml). Embryo biopsies were performed at blastocyst stage (day 5/ 6). After the trophoectoderm biopsy, all embryos were vitrified. Main outcome was segmental aneuploidy rate among different male age groups (<41 y.o./ ≥40 y.o.). Lineal regression analysis was used for continuous parameters and Chi square was used for categorical variables. Main results and the role of chance Descriptive parameters showed no differences, particularly in sperm concentration (43.2±15.6 vs. 40.1±14.3) and sperm motility (27.3±13.7 vs. 29.7±14.8). Lineal regression analysis showed no significant differences in segmental aneuploidy rate (p = 0.542). Statistical model showed no significant differences among male age groups (1.28% (0.76-2.01) vs 1.10% (0.69-1.66) p = 0.542). Limitations, reasons for caution The study has been conducted in three different clinics, there could be some unknown cofounding factors. Wider implications of the findings Male age don’t have an impact on the embryo segmental aneuploidy rate in young/donors’ oocyte Trial registration number Not applicable

O-278 Medical and ethical perspectives of performing ovarian stimulation and oocyte cryopreservation for fertility preservation (FP) in adolescents: 5 years’ experience from a tertiary centre

Abstract Study question What are the medical and ethical challenges of performing ovarian stimulation and oocyte cryopreservation in adolescents and what are the barriers to provision? Summary answer Oocyte cryopreservation for benign and malignant indications in adolescents is associated with unique medical and ethical challenges. What is known already An improvement in childhood cancer survival, increased transgender care and benign conditions such as haemoglobinopathies requiring stem cell transplant have led to higher representation of adolescent birth-registered females in FP clinics. FP in adolescents has increased complexities, both physical (pubertal stage, diagnosis) and psychological (accepting diagnosis, processing information, decision-making). Concerns relate to reliability of AMH in adolescents, anticipated response to ovarian stimulation and oocyte quality. Counselling and consenting young people and their families about fertility decisions, often alongside receiving a life-changing diagnosis, is an ethically complex area. Assessing capacity to consent is not straightforward. We report our clinical experience. Study design, size, duration This was a retrospective, observational cohort study of 26 adolescent birth-registered females aged 13 to 18 years who underwent ovarian stimulation and oocyte cryopreservation in a specialist unit for fertility preservation between 2018 and 2022. The primary outcome was oocyte yield, secondary outcomes included complications and drop-out rate. Participants/materials, setting, methods We included post-pubertal adolescent birth-registered females aged 13 to 18 years who were referred for fertility preservation for high risk of gonadotoxicity from treatment and who commenced ovarian stimulation for oocyte cryopreservation. Data was retrieved from a prospectively managed database. We noted demographic data, ovarian reserve, method of monitoring, response to ovarian stimulation and oocyte cryopreservation and route of egg collection. Documentation on counselling conversations and psychological maturity was retrieved from clinical records. Main results and the role of chance There were a total of 29 ovarian stimulation cycles performed in 26 adolescent birth-registered females aged between 13 and 18 years. Indications for fertility preservation included malignancy 62% (16/26), immunological disorders 19% (5/26), gender reassignment treatment 8% (2/26), recurrent ovarian cyst surgery 8% (2/26) and benign haematological disease 4% (1/26). The youngest was aged 13 years and 10 months at the time of egg collection. Minimum time from menarche to ovarian stimulation was 11 months. 23% (6/26) adolescents had previously received chemotherapy. AMH was 2.8-37 pmol/L and AFC 2-36. AFC correlated well with AMH in the majority. Random-start was performed in 54% (14/26) and dual stimulation in 12% (3/26). Number of cryopreserved oocytes was 3-45 and number of MII oocytes cryopreserved 3-35. Ultrasound monitoring was performed transabdominally in 88% (23/26) and transvaginally in 12% (3/26). Egg collection was performed transvaginally in all cases in this cohort, comprising adolescents from varying ethnicities. All cycles proceeded to completion. There were no complications in any cycle, including the 42% (11/26) performed for haematological malignancy. All adolescents were counselled in association with a family member to obtain informed consent. All were assessed as able to comprehend discussions. Limitations, reasons for caution There is limited data on performing oocyte cryopreservation in adolescents. Further studies expanding on our findings are needed to support clinicians to perform oocyte cryopreservation in this population. Concerns remain regarding increased aneuploidy rates in this age group compared to women in their 20s. Livebirth outcome data is needed. Wider implications of the findings This is the largest case series to date. Post-pubertal adolescents as young as age 13 can undergo ovarian stimulation and oocyte cryopreservation. Transvaginal egg collection is an accepted procedure when counselled appropriately. Clinician experience, correct setting and funding enable a permissive environment for oocyte cryopreservation in this population. Trial registration number N/A

P-201 Developmental analysis of blastocysts with blastomere exclusion during compaction and its relationship to pregnancy outcomes and preimplantation genetic testing for aneuploidy results

Abstract Study question What effects do blastocysts with blastomere exclusion during compaction have on embryo morphokinetics, morphology grade, genetic testing for aneuploidy (PGT-A) results, and pregnancy outcomes? Summary answer Blastocysts with blastomere exclusion leads to delay blastulation and poor morphology grade, but does not affect pregnancy outcomes and euploidy in PGT-A. What is known already It has been reported that aneuploid blastomeres are excluded during compaction, which is a mechanism for chromosome repair in blastocysts through the exclusion of aneuploid cells.Furthermore, in this phenomenon, it is known that the first cleavage of embryos is often abnormal, in which three or more cells originate from a single cell division event.However, this phenomenon has not been reported in the evaluation of embryo morphokinetics, artificial intelligence (AI) scores, or PGT-A results. Study design, size, duration In this retrospective study, we analyzed clinical medical reports at the Takahashi Women’s Clinic in Japan. We included 934 blastocysts cultured in a time-lapse incubator (EmbryoScope) after intracytoplasmic sperm injection (ICSI) from January 2018 to June 2021. Participants/materials, setting, methods Blastocysts cultured using a time-lapse incubator (EmbryoScope) after ICSI were classified into a control group (N = 515) with blastomere compaction or a BE group (N = 419) with blastomere exclusion during compaction. The first type of cleavage, AI score (IDAScore), embryo morphokinetics, and single frozen-thawed blastocyst transfer outcome were evaluated.Logistic regression analysis was performed to compare the two groups, considering patient age, blastocyst grade (Gardner classification), culture days, body mass index, and basal anti-Müllerian hormone level. Main results and the role of chance Comparing the control and BE groups, the first cleavage abnormality rate was 16.9% vs. 67.3% (P < 0.001), the percentage with good embryo grade (Gardner criteria ≧BB) was 93.4% vs. 61.0% (P < 0.001), and the mean score by AI analysis was 8.3 ± 1.3 vs. 6.4 ± 1.9 (P < 0.001), respectively. The BE group had a higher rate of abnormal cleavage and a significantly worse embryo grade and AI score than the control group.In the evaluation of embryo morphokinetics, the time to morula was 84.2 ± 7.0 h vs. 89.0 ± 8.5 h (P < 0.05) and time to blastocyst was 105.9 ± 9.4 h vs. 114.7 ± 11.4 h (P < 0.05). The BE group significantly delayed blastulation compared to the control group.The euploidy, mosaicism, and aneuploidy rates of PGT-A were 13.6% (9/66), 9.1% (6/66), and 77.3% (51/66) in the control group vs. 13.2% (5/38), 13.2% (5/38), and 73.7% (28/38) in the BE group, respectively. There was no significant difference in the PGT-A results between the two groups. Furthermore, the single-blastocyst transfer pregnancy rates (gestational sac with heart activity) in the control and BE groups were 47.1% (147/312) and 32.6% (60/184), respectively. Pregnancy rate was lower in the BE group, but was not significantly different from that of the control group. Limitations, reasons for caution The study was conducted at a single in vitro fertilization center. Embryo transfer results were based on ongoing pregnancies, while live birth data for all pregnancies are not yet available. Wider implications of the findings Although the BE group was graded worse, statistical analysis considering the grade showed no significant difference in PGT-A and pregnancy rates between the two groups.These results suggest that blastocysts with blastomere exclusion can be useful as transferable embryos if they grow to a transferable grade. Trial registration number not applicable

O-252 Genetic characterization of human sperm centrosome defects in infertile couples with complex embryo aneuploidy

Abstract Study question Can we characterize the genetic aspects related to sperm centrosome dysfunction in couples with high embryo aneuploidy that cannot exclusively be attributed to the oocyte? Summary answer We characterized structural and genomic abnormalities responsible for sperm centrosome dysfunction in infertile couples with complex embryo aneuploidy not exclusively related to the female partner. What is known already Conventional semen analysis provides only limited information on the proper function and embryo developmental competence of the male gamete. Therefore, an ancillary test, such as sperm chromatin fragmentation (SCF) and particularly double-stranded DNA breaks, has been claimed responsible for structural chromosomal abnormalities. It remains puzzling the source of complex embryo aneuploidy and chaotic chromosomal mosaicism that cannot solely be attributed to the female partner. The availability of genomic analysis may shed light on the integrity and function of the sperm centrosome responsible for ordaining chromosomal distribution at the first mitotic division. Study design, size, duration In the past 4 years, we identified 13 couples with unexpected high poor embryo cleavage resulting in a higher number of embryos with complex aneuploidy not solely attributable to the female gamete, resulting in extremely poor embryo implantation. Therefore, ancillary testing on the spermatozoa of the male partners was carried out to determine if the couple’s reproductive failure was eventually due to a stealth male gamete deficiency. Participants/materials, setting, methods Thirteen couples with poor clinical outcomes, characterized by poor embryo cleavage, high and complex embryo aneuploidy not exclusively due to the oocyte, with poor embryo implantation in multiple IVF/ICSI cycles, were offered adjuvant male partner testing including centrosome assessment through immunofluorescence staining on centrin (normal ≥ 60%), sperm chromatin fragmentation testing through terminal deoxynucleotide dUTP transferase nick-end labeling (TUNEL, normal ≤ 15%), transmission electron microscopy (TEM), and whole exome sequencing (WES) on spermatozoal DNA. Main results and the role of chance In 13 couples with an average paternal age of 38.1±2 years, semen analysis revealed a volume of 22.2±1.4mL, concentration of 58.2±37x10^6/mL, motility of 35.2±18% and normal morphology of 2.6±1%. They underwent with female partners (maternal age of 37.2±2 years) a total of 16 ICSI cycles with aneuploidy testing. Only 11 cycles yielded embryos for transfer due to poor embryo development with high aneuploidy rate, and none of them achieved a pregnancy. Centrosome staining revealed that only 45.8±22% of the spermatozoa displayed this key organelle. An overall SCF was observed at 16.7±10%. TEM confirmed that approximately 70% of the spermatozoa had irregular proximal centrioles. Moreover, genomic analysis by WES revealed mutations on PLK4 gene responsible for centriole duplication, BRSK1 gene involved in centrosome duplication, TUBGCP6 gene responsible for centrosomal microtubule nucleation, MARK4 for centrosome localization, MAP1S for microtubule anchoring and DNA binding, RIC8A for chromosome distribution, and CALM3 for cytokinesis. Of this cohort, 3 couples that subsequently underwent 3 ICSI cycles had their spermatozoa processed by microfluidics, aiming at selecting male gametes with higher genomic integrity. A fertilization rate of 78.3% (18/23) was achieved generating euploid embryos that resulted in 3 successful pregnancies. Limitations, reasons for caution We identified sperm centrosome dysfunction responsible for the peculiar and recurrent embryo aneuploidy. Although we identified shared gene mutations in those couples, these data are still preliminary. With exception of improving spermatozoa selection, there is a lack of a single effective treatment option to address sperm centrosome abnormality. Wider implications of the findings Ancillary tests with semen analysis were able to assess the function and competence of the male gamete. Corroborative genomic study can help provide insights into the reason for poor embryo implantation particularly those with high complex aneuploidy. Trial registration number Not applicable

Association of embryo aneuploidy and sperm DNA damage in unexplained recurrent implantation failure patients under NGS-based PGT-A cycles.

Recurrent implantation failure (RIF) is one of the most common conditions affecting In Vitro Fertilization (IVF)/Intracytoplasmic sperm injection (ICSI) outcomes. Aneuploidy embryos, one of the main types of embryos-related factors, was reported to be a major contributor to RIF. The present study aimed to examine the association between sperm DNA fragmentation index (DFI) and outcomes of next-generation sequencing (NGS)-based preimplantation genetic testing for aneuploidy (PGT-A) in unexplained RIF patients. This study analyzed 119 couples with unexplained RIF who underwent 119 PGT-A cycles between January, 2017 and March, 2022. The 119 males were divided into 3 groups according to their sperm DFI levels: Group1 (low, DFI ≤ 15%, n = 50), Group2 (medium, 15% < DFI < 30%, n = 41) and Group3 (high, DFI ≥ 30%, n = 28). Sperm DFI was measured by sperm chromatin structure analysis (SCSA) technique. Trophectoderm biopsy on day 5 or 6 were performed with NGS technique. The following outcomes of PGT-A were analyzed and compared: fertilization, good-quality embryos, aneuploidy rate, miscarriage, live birth and newborn defects. The component of aneuploidy embryos was significantly higher in high DFI group (42.71%) than that of medium group (28.39%) and low group (27.80%). The miscarriage rate of high DFI group (27.27%) and medium group (14.29%) is significantly higher than that of low group (0.00%). No significant differences were found regarding fertility, good-quality embryo rate, pregnancy rate, live birth rate or newborn defects among three groups. The sperm DNA damage is associated with blastocyst aneuploidy and miscarriage rate in unexplained RIF cases. Embryo selection by PGT-A and efforts to decrease sperm DFI before IVF/ICSI treatments should be considered for those male patients with high DFI.

Impact of male age on paternal aneuploidy: single-nucleotide polymorphism microarray outcomes following blastocyst biopsy

Does advanced paternal age (APA; ≥40 years) contribute to a higher incidence of paternal origin aneuploidy in preimplantation embryos? This was a multicentre retrospective study of single-nucleotide polymorphism (SNP) microarray (Natera and Karyomapping) preimplantation genetic testing (PGT) outcomes of blastocyst-stage embryos. Whole-chromosome aneuploidy analysis was performed on 2409 embryos from 389 male patients undertaking 681 assisted reproductive technology (ART) cycles between 2012-2021. Segmental aneuploidy analysis was performed on 867 embryos from 140 men undertaking 242 ART cycles between 2016-2021. Embryos were grouped based on paternal age at sperm collection: <35, 35-39 and ≥40 years. Paternal and maternal origin aneuploidy rates were compared between groups using chi-squared and/or Fisher's exact tests. There was no significant difference across groups in paternal origin whole-chromosome aneuploidy rate, overall (P=0.7561) or when segregated by type (trisomy and monosomy: P=0.2235 and 0.8156) or complexity (single versus 2, 3 or ≥4 aneuploidies: P=0.9733, 0.7517, 0.669 and 0.1481). Conversely, maternal origin whole-chromosome aneuploidy rate differed across groups (P<0.0001) in alignment with differing mean maternal age (P<0.001). Paternal origin deletions were 2.9-fold higher than maternal origin deletions (P=0.0084), independent of age stratification. No significant difference in paternal origin deletions was observed with APA ≥40 compared with the younger age groups (4.8% versus 2.5% and 2.8%, P=0.5292). Individual chromosome aneuploidy rates were too low to perform statistical comparisons. No significant association was found between APA and the incidence of paternal origin aneuploidy in preimplantation embryos, irrespective of type or complexity. Thus, APA may not be an indication for PGT.

Cell-Free Fetal DNA for Genetic Evaluation in Copenhagen Pregnancy Loss Study (COPL): A Prospective Cohort Study

(Abstracted from Lancet 2023;401:762–771 Spontaneous pregnancy loss occurs in approximately 1 in 4 pregnancies; however, diagnostic workup is mostly restricted to women with recurrent pregnancy loss. The lack of workup on first pregnancy loss is likely a result of the high de novo fetal aneuploidy rate; however, this ignores the association of euploid pregnancy loss with an increased risk of future losses.

The effect of sperm DNA fragmentation on the incidence and origin of whole and segmental chromosomal aneuploidies in human embryos.

Whether sperm DNA fragmentation (SDF) affects embryo development and clinical outcomes is still controversial, which limits the utility of SDF testing in assisted reproductive technology management. This study demonstrates that high SDF is associated with the incidence of segmental chromosomal aneuploidy and increased paternal whole chromosomal aneuploidies. We aimed to investigate the correlation of sperm DNA fragmentation (SDF) with the incidence and paternal origin of whole and segmental chromosomal aneuploidies of embryos at the blastocyst stage. A retrospective cohort study was conducted with a total of 174 couples (women aged 35 years or younger) who underwent 238 cycles (including 748 blastocysts) of preimplantation genetic testing for monogenic diseases (PGT-M). All subjects were divided into two groups based on the sperm DNA fragmentation index (DFI) level: low DFI (<27%) and high DFI (≥27%). The rates of euploidy, whole chromosomal aneuploidy, segmental chromosomal aneuploidy, mosaicism, parental origin of aneuploidy, fertilization, cleavage, and blastocyst formation were compared between low- and high-DFI groups. We found no significant differences in fertilization, cleavage, or blastocyst formation between the two groups. Compared to that in the low-DFI group, segmental chromosomal aneuploidy rate was significantly higher in the high-DFI group (11.57% vs 5.83%, P = 0.021; OR: 2.32, 95% CI: 1.10-4.89, P = 0.028). The whole chromosomal embryonic aneuploidy of paternal origin was significantly higher in cycles with high DFI than in cycles with low DFI (46.43% vs 23.33%, P = 0.018; OR: 4.32, 95% CI: 1.06-17.66, P = 0.041). However, the segmental chromosomal aneuploidy of paternal origin was not significantly different between the two groups (71.43% vs 78.05%, P = 0.615; OR: 1.01, 95% CI: 0.16-6.40, P = 0.995). In conclusion, our results suggested that high SDF was associated with the incidence of segmental chromosomal aneuploidy and increased paternal whole chromosomal aneuploidies in embryos.

ART outcomes in lean compared to obese phenotypes of polycystic ovarian syndrome.

To investigate differences in reproductive outcomes among IVF patients with lean compared to obese polycystic ovarian syndrome (PCOS) phenotypes. A retrospective cohort study of patients with PCOS who underwent IVF in a single, academically affiliated infertility center in the USA between December 2014 and July 2020. The diagnosis of PCOS was assigned based on Rotterdam criteria. Patients were designated as lean (< 25) or overweight/obese (≥ 25) PCOS phenotype based on BMI (kg/m2) at cycle start. Baseline clinical and endocrinologic laboratory panel, cycle characteristics, and reproductive outcomes were analyzed. The cumulative live birth rate included up to 6 consecutives cycles. A Cox proportional hazards model and Kaplan-Meier curve for estimating live birth rates were used to compare the two phenotypes. A total of 1395 patients who underwent 2348 IVF cycles were included. The mean (SD) BMI was 22.7 (2.4) in the lean and 33.8 (6.0) in the obese group (p < 0.001). A number of endocrinological parameters were similar between lean and obese phenotypes: total testosterone 30.8ng/dl (19.5) vs 34.1 (21.9), p > 0.02 and pre-cycle hemoglobin A1C 5.33% (0.38) vs 5.51% (0.51) p > 0.001, respectively. The CLBR was higher in those with a lean PCOS phenotype: 61.7% (373/604) vs 54.0% (764/1414) respectively. Miscarriage rates were significantly higher for O-PCOS patients (19.7% (214/1084) vs 14.5% (82/563) p < 0.001) and the rate of aneuploids was similar (43.5%, 43.8%, p = 0.8). A Kaplan-Meier curve estimating the proportion of patients with a live birth was higher in the lean group (log-rank test p = 0.013). After adjusting for potential confounders, the lean phenotype was associated with an increased hazard ratio for live birth: HR = 1.38 p < 0.001. Lean PCOS phenotype is associated with a significantly higher CLBR compared to their obese counterparts. Miscarriage rates were significantly higher among obese patients, despite comparable pre-cycle HBA1C and similar aneuploidy rates in patients who underwent PGT-A.

Comparison of results of prenatal diagnosis by different techniques for fetuses with increased nuchal translucency

To assess the value of chromosomal microarray analysis (CMA) and trio-whole exome sequencing (trio-WES) for fetuses with increased nuchal translucency (NT) thickness. Sixty two pregnant women who had visited Urumqi Maternal and Child Care Health Hospital between June 2018 and June 2020 for NT ≥ 3.0 mm at 11 ~ 13+6 gestational weeks were selected as study subjects. Relevant clinical data were collected. The patients were divided into 3.0 ~ ＜3.5 mm (n = 33) and ≥3.5 mm groups (n = 29). Chromosome karyotyping analysis and chromosomal microarray analysis were carried out. And trio-WES analysis was performed on 15 samples with NT thickening but negative CMA results. The distribution and incidence of chromosomal abnormalities in the two groups were compared by using chi-square test. The median age of the pregnant women was 29 years old (22 ~ 41 years old), the median thickness of NT was 3.4 mm (3.0 ~ 9.1 mm), and the median gestational age at the detection was 13+4 weeks (11+5 ~ 13+6 weeks). Chromosome karyotyping analysis has detected 12 cases of aneuploidies and 1 case of derivative chromosome. The detection rate was 20.97% (13/62). CMA has detected 12 cases of aneuploidies, 1 case of pathogenic CNV and 5 cases of variant of uncertain significance (VUS), with a detection rate of 29.03% (18/62). The aneuploidy rate for the NT ≥ 3.5 mm group was higher than that for the 3.0 ≤ NT < 3.5 mm group [3.03% (1/33) vs. 41.38% (12/29), χ² = 13.698, P < 0.001]. There was no statistically significant difference between the two groups in the detection rate of fetal pathogenic CNV and VUS (χ² = 0.028, P > 0.05). Trio-WES analysis of 15 samples with negative CMA result and no structural abnormality has identified 6 heterozygous variants, including SOS1: c.3542C>T (p.A1181V) and c.3817C>G (p.L1273V), COL2A1: c.436C>T (p.P146S) and c.3700G>A (p.D1234N), LZTR1: c.1496T>C (p.V499A), and BRAF: c.64G>A (p.D22N), respectively. Based on the guidelines from the American College of Medical Genetics and Genomics (ACMG), all of the variants were rated as VUS. NT thickening can indicate chromosome abnormality, and CMA and trio-WES may be used for the prenatal diagnosis.

Prenatal diagnosis of non-mosaic sex chromosome abnormalities: a 10-year experience from a tertiary referral center.

The aim of this study was to explore the frequency and profile of non-mosaic sex chromosome abnormalities detected in prenatal diagnosis over the past 10 years. We retrospectively reviewed pregnancies diagnosed with non-mosaic sex chromosome abnormalities between January 2012 and December 2021, using karyotyping and/or single nucleotide polymorphism (SNP) array. Maternal age, indications for testing, and outcomes were recorded. Traditional karyotyping identified 269 (0.90 %) cases of non-mosaic sex chromosome abnormalities among 29,832 fetuses, including 249 cases of numerical abnormalities, 15 unbalanced structural abnormalities, and 5 balanced structural abnormalities. The overall detection rate of common sex chromosome aneuploidies (SCAs) was 0.81 %, with 47,XXY, 47,XXX, 47,XYY, and 45,X accounting for 0.32 , 0.19, 0.17, and 0.13 % respectively. All showed a fluctuating upward trend over the study period, except for 45,X. During the first five years (2012-2016), the major indication for testing was advanced maternal age (AMA), followed by abnormal ultrasound, abnormal noninvasive prenatal testing (NIPT), and abnormal maternal serum screening (MSS). In the second five years (2017-2021), the most frequent indication was abnormal NIPT, followed by AMA, abnormal ultrasound, and abnormal MSS. Among the 7,780 cases that underwent SNP array in parallel, an additional 29 clinically significant aberrations were detected. The most frequent aberration was a microdeletion in the Xp22.31 region, which was associated with X-linked ichthyosis. Fetal sex chromosome abnormalities are important findings in prenatal diagnosis. The application of NIPT and SNP array technology has greatly improved the detection of SCAs and submicroscopic aberrations associated with sex chromosomes.

Undetected Maternal Cell Contamination in Products of Conception Analysis May Mask Recurrence Risks for Future Pregnancies: A Case Report and Discussion [ID: 1377203

INTRODUCTION: Maternal cell contamination (MCC) in products of conception (POC) tissue is common; some studies report 59% of 46,XX results represent MCC. METHODS: Products of conception tissue and maternal blood samples were shipped to a laboratory for genotyping using Illumina CytoSNP-12b microarrays and bioinformatics (IRB E&amp;I 19040-03A). Patient informed consent was obtained for submission of a case report. RESULTS: A 25-year-old woman with a family history of recurrent pregnancy loss (RPL) was first offered POC analysis after her second loss. The result was normal female; however, MCC could not be ruled out because a maternal sample was not provided. Thus, the result was presumed normal, and the patient was informed her testing did not identify a genetic cause for her loss. The patient's third miscarriage was sent for POC analysis with a parental sample, which identified a maternally derived 26.8-Mb terminal deletion and 39.3-Mb terminal duplication of chromosome 4. The submitted maternal sample allowed for reanalysis of the second loss confirming MCC. Maternal karyotype analysis revealed an abnormal result: 46,XX,inv(4)(p15.2q31.3). The patient was referred to reproductive endocrinology for discussion of options, including in vitro fertilization with preimplantation genetic testing. CONCLUSION: Undetected MCC can lead to erroneous normal female results, masking fetal findings that could affect recurrence risks. Since 5% of couples with RPL have a balanced chromosome rearrangement, almost six couples for every 1,000 losses are at risk for undetected MCC masking recurrence risks (calculated using a 50% expected aneuploidy rate and 59% of 46,XX results actually representing MCC).