Preimplantation Genetic Diagnosis Research Articles

Ethical Reflections on Preimplantation Genetic Diagnoses

With fertility rates at an all-time low, children have become even more the 'treasures' of their families. Progress in genetic selection technology has made preimplantation genetic diagnosis an increasingly common practice in clinics. However, the practice of purposively selecting genes for future children remains controversial. In this article, the process of preimplantation genetic diagnosis is introduced and related philosophical and social perspectives are reviewed. Finally, the ethics related to this practice are discussed in the contexts of obligation theory, utility theory, and four ethical principles. The authors hope this article sheds light on the diverse perspectives used to consider and discuss the ethical issues surrounding gene selection and, importantly, helps nurses provide care grounded in ethics and humanity in ethically uncertain circumstances.

Family Planning in Genetic Optic Atrophies in Israel, a Case Series and a Discussion of Ethical Considerations.

Patients with genetic optic atrophies must navigate all stages of life with their visual impairment, including the important milestone of family planning. Advances in genetic testing now allows physicians and affected families to consider medical help with the aim of preventing blindness through preconception, preimplantation, and perinatal methods. This case series presents 4 patients with different genetic optic atrophies (Leber hereditary optic neuropathy [LHON], autosomal dominant optic atrophy, Wolfram syndrome, and papillorenal syndrome) who were followed by the Neuro-Ophthalmology Unit at a tertiary medical center between 2010 and 2023 and were of child-bearing age. The aim of this study was to increase understanding in family planning options for patients with optic atrophies, raise awareness of the solutions available, and provide guidance for clinicians to support their patients. Advances in medicine, genetics, and medical technology allow multidisciplinary teams to assist patients in fulfilling their desire for a genetically healthy offspring. Customized solutions can be designed to meet the specific challenges posed by each type of genetic optic atrophy. The solutions proposed in this series are based on genetic testing done in the parents, which then allows to plan medical and genetic intervention individually. The solutions opted for in this series range from the decision to not have another child until PGD (Preimplantation genetic diagnosis). We describe how genetic advancements have made it possible for patients with the 4 most common hereditary optic atrophies to fulfill their wish to have children without visually threatening genetic mutations. We also review the recent literature on the penetrance of optic atrophy in OA-mutation carriers and raise 2 significant ethical considerations: the reduction of a future life to a non-life-threatening impairment and that of public expenditure for non-life-threatening conditions.

Maternal Placental Growth Factor (PlGF) levels, sonographic placental parameters, and outcomes of IVF pregnancies with and without embryo trophectoderm biopsy.

In vitro fertilization (IVF) is associated with abnormal trophoblast invasion and resultant decreased levels of circulating placental biomarkers such as placental growth factor (PlGF).Our objective was to evaluate maternal serum levels of second/third trimester PlGF, sonographic placental parameters, and clinical outcomes among IVF frozen embryo transfer (FET) pregnancies with and without embryo trophectoderm biopsy. This was a retrospective study of pregnant patients who conceived using a single frozen embryo transfer (FET) and gave birth between 30 January 2018 and 31 May 2021. We compared PlGF levels, sonographic placental parameters, and clinical outcomes between FET with biopsy and FET without biopsy groups. The median PlGF level was 614.5 pg/mL (IQR 406-1020) for FET pregnancies with biopsy, and 717.0 pg/mL (IQR 552-1215) for FET pregnancies without biopsy. The adjusted mean difference was 190.9 pg/mL lower in the FET biopsy group (95% CI, -410.6, 28.8; p = 0.088). There were no statistically significant differences in placental parameters or clinical pregnancy outcomes. This exploratory study demonstrated a possible trend toward lower maternal serum PlGF in the pregnancies conceived with FET using a biopsied embryo. Further investigation is warranted into the potential placental health effects of trophectoderm biopsy.

The sufficiency of genetic diagnosis in managing patients with inborn errors of immunity during prenatal care and childbearing.

Individuals with inborn errors of immunity face challenges in fertility, pregnancy, and genetic disorder transmission. Prenatal genetic counseling is crucial, especially in tribal societies with consanguineous unions. Ten families with confirmed inborn errors of immunity were studied, revealing diverse pregnancy decisions: An architect with autosomal dominant STAT-1 gain of function underwent prenatal diagnosis despite initial plans for preimplantation genetic diagnosis. In a consanguineous family, two children died from leukocyte adhesion deficiency type 1 because the father refused prenatal diagnosis. First cousins opted against terminating the second pregnancy, resulting in two children affected by Bruton disease. Another consanguineous couple, with two children afflicted by ataxia-telangiectasia, chose oocyte donation for their third child, ensuring a healthy birth. Recurrent pregnancy loss was observed in a mother subsequently diagnosed with ZAP70 deficiency. A mother with Wiskott-Aldrich syndrome child opted for in vitro fertilization, leading to a healthy birth post-prenatal diagnosis. A misdiagnosis of anaplastic anemia occurred in a family with multiple instances of Wiskott-Aldrich syndrome. A leukocyte adhesion deficiency type 1 case led to parental dissolution due to the father's refusal to acknowledge the condition. In a non-consanguineous couple, the father's diagnosis of TACI deficiency influenced the mother's decision to discontinue pregnancy post-prenatal diagnosis. Genetic diagnosis alone cannot optimize prenatal care for immune dysregulation disorders. Various factors, including patient education, societal norms, ethics, and economics, impact pregnancy decisions. Clinical immunologists must integrate these elements into guidance strategies to enhance patient outcomes.

New Variants Identified by Next-Generation Sequencing in Polycystic Kidney Disease Patients.

Polycystic kidney disease (PKD) is a common inherited disease characterized by multiple cysts in kidneys and various extra renal manifestations. Molecular diagnosis plays a crucial role in confirming both the clinical diagnosis and preimplantation genetic diagnosis furthermore, selecting appropriate treatment options. This study aimed to expand the understanding of genetic mutations in patients with polycystic kidney disease and to improve the management of patients. The study included 92 patients with a clinical diagnosis of PKD based on renal ultrasound criteria. Targeted next-generation sequencing was performed using a custom panel kit. Of the 92 patients included in the study, pathogenic/likely pathogenic variants of the PKD1, PKD2 genes were detected in 37 patients (40.2%), while 8 patients (8.6%) had variants with uncertain clinical significance. After the additional assessment of pathogenic/likely pathogenic variants, it was found that 15 of the variants in PKD1 and 2 of the variants in PKD2 have not been reported in the literature previously. Additionally, pathogenic variants, 5 of which were novel, have been identified in different genes in 8 patients. This study presented the largest patient cohort conducted in Turkey. These findings were significant in expanding our understanding of the genetic variations associated with polycystic kidney disease. The study contrıbuted the literature data on polycystic kidney disease by reporting important findings that could pave the way for further investigations in the diagnosis, treatment, and management of the affected patients.

P-124 Machine learning scores reveal mosaic embryo quality as the key predictor for live births, outperforming mosaicism characteristics in ART success

Abstract Study question Is it possible to score the mosaic embryos in order to prioritise them according to their pregnancy potencial? Summary answer The machine-learning score underscores the crucial role of embryo quality over mosaicism, prioritizing high-quality, day-5 biopsied embryos for enhanced live birth outcomes in ART. What is known already After embryo biopsy and PGT-A analysis, embryos can be classified as euploid, aneuploid, or mosaic, wherein a combination of chromosomally normal and altered cells is detected. The transfer of mosaic embryos has been controversial, but currently, the recommendations of international scientific societies, including ESHRE, advocate for their transfer. In case of pregnancy, a prenatal test is advised to rule out any chromosomal aberration. The non-transfer of these embryos reduces ART success chances, as chromosomally normal children may be born from them. Study design, size, duration The study design is observational and retrospective. A total of 8346 embryos from 2583 PGT-A cycles were considered (January-2017 to January-2023). Only transferred mosaic embryos (n = 263) were included in the study. The trophectoderm biopsies of D5, D6, or D7 blastocysts were analyzed by NGS using the Illumina platform (VeriSeq Illumina®, San Diego, CA, USA). The biopsied embryos were vitrified and transferred in a subsequent cycle. Participants/materials, setting, methods The primary indications for PGT-A included advanced maternal age, abnormal sperm FISH, and recurrent miscarriage or implantation failure. Clinical outcomes, along with variables related to progenitors, embryos, biopsy, ovarian stimulation, and adjuvant treatments, were recorded in a database. Machine learning models were conducted using R statistical software (v.4.3.1), and the ‘Caret’ library was utilized to implement different algorithms. ‘Autoscore,’ as an interpretable scoring tool, combined machine learning and regression modeling. Main results and the role of chance The mean maternal and paternal ages were 34.95±6.38 and 39.13±6.74 years. Biopsies were predominantly performed on day 5 (61%). Additionally, 44% of embryos were of A quality, and 49% were of B quality. Regarding clinical outcomes for mosaic embryos, biochemical, clinical pregnancy, and live birth rates were 51%, 41%, and 36%, respectively. The features used to generate the score included those related to embryo quality, biopsy, and mosaicism. Through 10-fold cross-validation, the study identified top-ranking predictors maximizing the AUC of the predictive model. The highest weight in the score was assigned to embryo quality (42%) and day of biopsy (34%), with lower weights for factors related to mosaicism: monosomy and/or trisomy (18%) and mosaicism level (6%). The machine-learning score indicates that, in transferring embryos with mosaicism, priority should be given to high-quality embryos biopsied on day 5. The type and level of mosaicism have a minor impact on the embryo’s gestational capacity, becoming relevant only when prioritizing embryos of identical quality. In such cases, embryos with lower mosaicism degrees and no monosomy demonstrate higher implantation potential. Limitations, reasons for caution The inherent limitations of a retrospective analysis highlight the need for prospective randomized studies to confirm the validity and usefulness of the mosaic embryo transfer score. Wider implications of the findings A scoring system has been developed to prioritize the transfer of mosaic embryos. The crucial variables are associated with embryo quality and the day of biopsy, reflecting the progression of embryonic development. Conversely, variables related to mosaicism play a secondary role. Trial registration number Not applicable

P-233 Embryo transfer timing and clinical pregnancy success: a retrospective study

Abstract Study question The aim of this study is to compare the clinical outcome of day5 versus day6 genetically normal blastocyst transfers. Summary answer 1000 oocytes were analyzed showing a highly significant difference in the number of normal embryos and clinical pregnancy rates in day5 versus day6 blastocysts What is known already studies have shown that day 5 embryos have a higher pregnancy rate compared to day 6 embryos, some studies had only euploid embryos transferred and others did not have any genetic testing done on embryos. No study had a sample size as large as 1760 and the number of embryos studied was a limiting factor in their results. Study design, size, duration The study is a retrospective cross-sectional chart review with multivariate analysis, data from January 2019 up to February 2023 were extracted. 1760 patients were recruited, 1000 in the day5 group and 760 in the day6 group. The data recorded for each patient included maternal age, body mass index (BMI), anti-Müllerian hormone (AMH) level, number, prenatal genetic diagnostic testing, frozen embryo transfer, sperm parameters, and pregnancy status. Participants/materials, setting, methods All embryos were genetically tested for aneuploidy before transfer, using next-generation sequencing technology to rule out 24-chromosome aneuploidies (1-22, X, Y). All patients who have single embryo transfer, frozen embryos and pre-implantation genetic diagnosis (PGD) were included in the study. Continuous variables were expressed as mean with standard deviation and categorical variables as numbers and frequencies (percentages). Statistical differences between groups were estimated using the chi-square or Fisher’s test. All analyses were performed using SAS studio. Main results and the role of chance 1,000 cycles were analyzed for Day 5 and 760 for Day 6 embryo. The number of blastocysts formed, and genetically diagnosed embryos significantly favor the Day 5 group. There’s a significant difference in the number of normal embryos, with the Day 5 group having more. There is a highly significant difference in clinical pregnancy rates. On the other hand, the differences in biochemical pregnancies are not statistically significant. The occurrence of ectopic pregnancies shows no significant difference. Additionally, there is no statistically significant difference in the rates of miscarriage. There is a highly significant difference in blastocyst formation rates, with Day 5 embryos. This indicates that Day 5 embryos have a significantly higher likelihood of forming blastocysts compared to Day 6 embryos. Implantation: Day 5 embryos have an implantation rate of 62.0% compared to 49.7% for Day 6 embryos. Day 5 embryos exhibit a significantly higher likelihood of successful implantation. Euploid: The difference in euploid rates is statistically significant, albeit with a lower p-value of 0.0236. Day 5 embryos have a rate of 59.6%, while Day 6 embryos have a rate of 56.0%. Day 5 embryos are associated with a lower likelihood of being aneuploid Limitations, reasons for caution Limitation of this study is that we do not have data available regarding complications during pregnancy in the day 5 versus day 6 groups and we had no data regarding the the live birth rate between the two groups. Wider implications of the findings This study has the potential to revolutionize worldwide discussions during IVF consultations. With the large sample size we can provide for the first time a statistically significant difference in the percentage of success when transferring a day5 (61%) versus day6 (49%) euploid embryo. Trial registration number not applicable

P-735 Is Artificial Intelligence (AI) currently able to provide evidence-based scientific responses on methods that can improve the outcomes of embryo transfers?

Abstract Study question Could chatbots potentially be used as tools for both patients’ and physicians’ education in an infertility journey? Summary answer Artificial Intelligence (AI) is not yet in a position to give clear, evidence-based recommendations in the field of fertility, particularly concerning embryo transfer. What is known already The rapid development of AI has raised questions about its potential uses in different sectors of everyday life. Individuals from diverse fields have tried to incorporate its usage in their personal but also in their professional lives, with varying levels of success. Specifically in medicine, ChatGPT has been studied intensely with more than 400 related articles having been indexed in PubMed until May 2023, while AI has reportedly also succeeded in several standardized medical tests and passed several Medical Board examinations. Hence the question arises whether chatbots could be used as tools for clinical decision-making or patients’ and physicians’ education. Study design, size, duration We used nine of the most popular free AI chatbots available (ChatGPT, Bard, Writesonic, You, Perplexity, Learnt, Bing, Magickpen, and Rytr) and entered the following command: “Write me a 300-word scientific essay about evidence-based methods that can improve the outcomes of embryo transfer” in May 2023. We collected the responses and extracted the methods each chatbot suggested. When sufficient similarity among answers was present we categorized the answers under one category to facilitate the study. Participants/materials, setting, methods We calculated descriptive statistics and the prevalence of each response. We used as a comparator for widely acceptable practices that are proven to improve embryo transfer outcomes the 2017 ASRM guideline on performing embryo transfer taking also into consideration more current literature. Data was compared using chi-squared tests and a level of p < 0.05 was used as the threshold of statistical significance. Main results and the role of chance The range of the recommendations was from one to nine per chatbot (median = 4, IQR = 2) with an average of 4.78 suggestions per chatbot. Out of a total of 43 recommendations, which could be grouped into 19 similar categories, only 3/19 (15.8%) were evidence-based practices, those being “ultrasound-guided embryo transfer”, which was also the most commonly appearing response, appearing in 7/9 (77.8%) chatbots, “single embryo transfer” appearing in 4/9 (44.4%) chatbots and “use of a soft catheter” in 2/9 (22.2%) chatbots. Some controversial responses appeared even more often than the two latter evidence-based ones with “preimplantation genetic testing (PGT)” being the second most common response with 6/9 chatbots suggesting it (66.7%) and the vague suggestion of “optimal endometrium preparation” being in the third place with 5/9 chatbots (55.6%), both non-evidence-based practices to improve embryo transfer. The majority of the recommendations were unique, with 10 answers appearing only once (1/9; 11.1%), those being “endometrial scratching”, “natural cycle embryo transfer”, “use of GnRH antagonist protocol”, “blastocyst transfer”, “use of specialized catheter”, “preimplantation genetic screening (PGS)”, “mock embryo transfer”, “uninterrupted embryo culture”, “minimizing transfer time”, and “maintaining temperature and pH of the culture media”. Limitations, reasons for caution Firstly, we only used some of the most popular chatbots and not all existing ones. Additionally, chatbots tend to give different answers when repeatedly asked the same questions. However, we believe that our study effectively captures the prevailing practices of chatbot users, who typically pose a question only once. Wider implications of the findings Both patients and physicians should be wary of guiding care based on chatbot recommendations in infertility since the majority of responses consists of scientifically unsupported recommendations. Chatbot results might improve with time especially if trained to obtain information from validated medical databases, however, this will have to be verified scientifically. Trial registration number N/A

P-503 Euploidy rate of day 4 fully developed blastocysts

Abstract Study question Do embryos that fully developed to blastocyst at day 4 have high aneuploidy rates as assessed by preimplantation genetic analysis? Summary answer Fully developed blastocysts at day 4 had a high euploidy rate. What is known already In ART, it is considered important to use good quality blastocysts to increase the pregnancy rate after embryo transfer. Some reports have demonstrated a high pregnancy rate for embryos that fully developed to blastocysts on day 4 after IVF (Ozgur et al., 2021). Furthermore, it has been reported that the speed of embryo development is related to the rate of chromosome aneuploidy (Taylor et al., 2014). There are though, limited reports on the euploidy rate of embryos developed to blastocysts at day 4. Study design, size, duration This retrospective study analyzed 763 embryos (from 184 PGT-A cases) that underwent TE biopsy on day 5 between January to December 2022 to determine their ploidy status. Participants/materials, setting, methods Embryos cultured in a time-lapse incubator were divided into two groups: those that developed to blastocyst (Gardner’s classification: ≥ expansion grade 3) at day 4 (96-100 h) (D4(+) group) and those that did not develop to full blastocyst at day 4 (D4(-) group) and the euploidy rates were compared. Statistical analysis was performed using Fisher’s exact test to determine significant differences (P < 0.05). Main results and the role of chance The euploidy rate of the D4(+) group was 36.5% (80/219), which was significantly higher than the D4(-) group, 23.3% (127/544) (p < 0.01). Moreover, when considering the age of the female, for age ≤39 years, the rates were significantly higher in the D4(+) group (52.1% (61/117) and 35.4% (97/274) p < 0.01 respectively ). For age 40≥ years, it tended to be higher but was not significantly different in the D4(+) group vs D4(-) group (18.6% 19/102 and 11.1% 30/270 respectively). Even when limited to embryos that were graded as good quality blastocysts at day 5, the D4(+) group was significantly higher (p < 0.01) than the D4(-) group (55.0% (60/109) vs 36.1% (90/249)). Limitations, reasons for caution This was a retrospective study limited to day 5 embryos with biopsies taken after vitrification-warming. Wider implications of the findings These results demonstrate that embryos that had already developed to blastocyst at day 4 had a higher rate of euploidy compared to day 5 blastocysts. Thus, when performing PGT-A, biopsy of embryos that have already developed to blastocyst at day 4 are expected to be prioritised for transfer. Trial registration number not applicable

P-318 Reproductive ageing: the seed, the soil, or both?

Abstract Study question Is it all about the embryo? Can a single euploid blastocyst transfer sustain reproductive outcomes in women with advanced reproductive age? Summary answer Despite euploid embryo transfer, endometrial senescence appears to play a crucial role in determining reproductive success, particularly in older patients undergoing in vitro fertilization (IVF). What is known already Advanced reproductive age significantly impairs oocyte and embryo quality. Effective crosstalk and synchronization between embryo and endometrium are pivotal for successful pregnancies, both in vivo and in vitro. Implantation failure remains a persistent challenge in IVF, exacerbated by delayed family planning trends. The transfer of euploid blastocysts through preimplantation genetic testing for aneuploidy (PGT-A) is a potential strategy to address implantation issues, decrease miscarriages, and shorten time-to-pregnancy. However, a significant proportion of IVF treatments remain unsuccessful, suggesting critical factors beyond the embryo. Study design, size, duration This retrospective study analyzed 457 single euploid blastocyst transfers performed by two doctors at a private IVF center from January to November 2023. Inclusion criteria encompassed cases with PGT-A indications (advanced maternal age, repeated implantation failure, recurrent pregnancy loss, etc.) or cases where embryo biopsy was patient-requested. The primary outcome was ongoing pregnancy rate (OPR), with secondary outcomes including pregnancy rate (PR) and clinical pregnancy rate (CPR). Participants/materials, setting, methods Participants were categorized into four groups: Group 1 (< 35 years old; N = 100), Group 2 (35-37 years old; N = 102), Group 3 (38-40 years old; N = 118), and Group 4 (> 41 years old; N = 87). A control group (oocyte donation; N = 50) with single euploid embryo transfers showed a mean recipient age of 43 years. Donors were always less than 32 years old. Endometrial preparation protocols were consistent across all groups. Chi-square test was used to compare groups. Main results and the role of chance Among the 457 transfers analyzed, with a mean female age of 37 years, the overall PR was 71.3%, CPR was 64.8%, and OPR was 60.2%. Groups showed no differences in demographic variables and cycle parameters. Group 1 demonstrated higher PR (83.3%), CPR (78.4%), and OPR (73.5%) compared to Group 2 (PR 70.9%, p = 0.034; CPR 66%, p = 0.047; OPR 62.1%, p = 0.081), Group 3 (PR 68.2%, p = 0.009; CPR 61.2%, p = 0.005; OPR 56.6%, p = 0.008), and Group 4 (PR 65%, p = 0.002; CPR 56.1%, p < 0.001; OPR 51.2%, p = 0.001). Furthermore, the control group (oocyte recipients) showed significantly lower PR (68%, p = 0.031), CPR (54%, p = 0.002), and OPR (46%, p < 0.001) compared to Group 1, but not with the other groups. These findings demonstrate that even with euploid embryos originating from young donors, older women exhibited lower pregnancy rates than young women transferring single euploid blastocysts from their own oocytes and similar rates compared to those with advanced reproductive age transferring their own euploid blastocysts, implying that endometrial ageing may disproportionately influence IVF treatment outcomes. Limitations, reasons for caution The retrospective design introduces inherent bias, notably selection bias and unmeasured confounders. This preliminary data did not account for male infertility factors and their impact on embryo quality. Wider implications of the findings Reproductive aging appears to be influenced by factors beyond the embryo itself, especially in women above 35 years. Further research is warranted to elucidate the causes and impact of reproductive aging on implantation potential, aiming to refine clinical practices and enhance the success of IVF treatments. Trial registration number not applicable

P-257 Building on a commercialized time-lapse algorithm to improve the predictive power for embryo ploidy status

Abstract Study question Would incorporating oocyte morphometric parameters into a predefined algorithmic model (KIDscore) enhance its ability to predict embryo ploidy status? Summary answer While larger oocyte area is significantly associated with embryo euploidy, its integration into a commercial algorithm did not add a clinical value to its predictivity. What is known already Currently, the genetic status of embryos is primarily assessed using preimplantation genetic testing for aneuploidy (PGT-A) following embryo biopsy. Concerns about potential harm to the embryo have spurred research into less invasive predictive tools, including time-lapse imaging (TLI). While numerous time-lapse data points have been explored, the literature is scarce when assessing the value of oocyte morphometric characteristic in predicting embryo euploidy. Study design, size, duration The study design was observational and retrospective. A total of 414 embryos from 98 cycles of preimplantation genetic testing for aneuploidies were included (January 2019 to December 2023). Participants/materials, setting, methods Trophectoderm samples were analyzed by preimplantation genetic testing for aneuploidies (PGT-A). Manually annotated time-lapse data points were recorded from which predictive models of embryo aneuploidy were developed. Measurements of the oocyte area were recorded and the automatic embryo KID scores calculated using an in-built commercial software. Multiple regression analyses were performed and a Receiver Operating Characteristic (ROC) analysis conducted. Main results and the role of chance The mean age of female participants included in the study was 34.5 ± 4.6 years. The rate of embryo aneuploidy detected was 41.8%. When a univariate analysis of different time-lapse data was performed, a large number of variables showed statistically significant differences between the euploid and aneuploid embryo groups. The mean oocyte area (µm2) in the euploid group was found to be significantly larger than in the aneuploid group (10151.4 ±621.6 vs 9915.3 ± 950.4; P < 0.01). There was also a significant positive association between oocyte area and embryo euploid status after adjusting for confounders (P <0.01). The Area Under the Curve (AUC) value was 0.62 for the aneuploidy explanatory model when oocyte area was combined with the KID score, compared to an AUC of 0.60 for the KID score alone. Although significant associations were detected, the predictive power of oocyte area measurement did not translate into a clinically useful value. Limitations, reasons for caution The limitations of this study stem from its retrospective nature. The low number of observations also limits the strength of the findings. Wider implications of the findings Although it is possible to predict embryo aneuploidy from some oocyte characteristics, the discriminatory power of designed time-lapse predictive models remained suboptimal for use in current clinical practice. Trial registration number Not applicable

P-552 Unveiling associated factors to in vitro embryonic ploidy: Insights from 8194 blastocysts by Next Generation Sequencing

Abstract Study question What factors are associated with an increased probability of having aneuploid or mosaic embryos in vitro? Summary answer Maternal age and biopsy day significantly influence aneuploidy, while trophectoderm quality impacts both aneuploidy and embryo mosaicism. What is known already Embryonic aneuploidy and mosaicism are critical factors affecting the success of in vitro fertilization. Several studies have demonstrated that advanced maternal age is the most important variable associated with chromosomal abnormalities. However, the influence of other factors, including the day of the blastocyst biopsy and the quality of specific embryonic components, such as the trophectoderm, on the likelihood of aneuploidy and mosaicism is less understood. Study design, size, duration This retrospective study involved the analysis of 8,194 blastocyst embryos derived from 2,180 IVF/ICSI cycles at a specialized assisted reproduction clinic. The study spanned 7 years, from 2017 to 2023, focusing on identifying factors influencing embryonic ploidy Participants/materials, setting, methods Retrospective analysis of 8194 blastocysts from 2180 IVF/ICSI cycles at a single fertility center. Evaluated maternal age, paternal age, day of embryo biopsy, inner cell mass and trophectoderm quality, embryo biopsy operator, fertilization technique, using logistic regression to assess impact on ploidy (euploid, aneuploid, mosaic). Analysis identified significant factors influencing ploidy, adjusting for confounders. Statistical significance at p < 0.05. Main results and the role of chance The analysis of 8,194 blastocyst embryos highlighted significant findings. Maternal age showed a considerable impact on aneuploidy with a p-value <0.001 and an odds ratio (OR) of 1.74, indicating a strong association. Similarly, the day of embryo biopsy was a significant factor (p < 0.001, OR = 1.51) emphasizing its influence on embryo aneuploidy. The quality of the trophectoderm was a crucial factor, with a notable correlation with both aneuploidy (p < 0.001, OR = 1.78) and mosaicism (p < 0.001, OR = 1.28). Further analysis was also performed to find the variables associated with mosaicism, and the only significant variable was quality of trophectoderm increasing the probability of mosaicism by 28%. These statistical values underscore the robustness of the study’s conclusions. The large sample size and the application of logistic regression models further minimized the role of chance, enhancing the reliability of these findings. The research provides significant insights into the factors influencing embryonic ploidy, extending beyond the well-recognized impact of maternal age. It underscores the importance of considering these variables in clinical assessments during fertility treatments, particularly in evaluating the risk of chromosomal abnormalities. Limitations, reasons for caution The study’s retrospective nature limits causal inferences. The findings need validation in prospective, multicenter studies to establish broader applicability and account for potential biases. Wider implications of the findings These results contribute to the understanding of the factors associated with aneuploidy and embryonic mosaicism, beyond maternal age. Integrating the day of embryo biopsy and trophectoderm quality as key factors into clinical evaluation that could improve clinical decision-making in fertility treatments, especially in assessing the risk of chromosomal abnormalities. Trial registration number Non-Clinical trials

P-451 Improvement and validation of a cost effective PGT-A test for the detection of aneuploidy, triploidy and mosaicism

Abstract Study question This study aims to validate a PGT-A platform to simultaneously sequence and genotype embryos to detect triploidy as well as high and low frequency mosaicism. Summary answer Previda Plus platform validation establishes the capability to concurrently identify aneuploidy, triploidy and mosaicism with high and low frequencies at a significantly reduced cost. What is known already Low pass sequencing platforms can identify with great accuracy monosomy and trisomy karyotypes from embryo biopsies by comparing DNA quantities across chromosomes, however, these platforms exhibit limitations in identifying triploidy since all chromosomes exhibit uniform concentration. Triploidy detection necessitates genotyping involving the detection of highly variable SNPs to distinguish different haplotypes. Intermediate copy number may represent putative mosaicism. Recent publications show that embryos with low-level mosaicism demonstrate comparable implantation rates to euploid embryos, therefore validating cut offs to differentiate between low-level and high-level mosaics from euploid and aneuploid embryos is necessary. Study design, size, duration To validate triploidy detection, we measured allele frequencies (AF) using a high frequency SNP panel. The SNP frequency profile of a diploid exhibits a mix of AF of 100% and 50%, while a triploid exhibits AF of 100%, 66%, and 33%. To validate mosaicism, cell lines that were diploid, trisomic, or monosomic for a specific chromosome were mixed in pairs in increments of 10% (From 0%:100% line-1:line-2, to 100%:0%) with multiple iterations of each combination. Participants/materials, setting, methods Fifteen cell lines (triploid or diploid) underwent amplification using a 384 highly variable SNP panel. Pooled SNP and PGT-A products underwent processing in a single sequencing workflow. Ploidy Scores (PS) were derived from the total number of SNPs, 66% and 33%, and cutoff values were established to discriminate between diploid and triploid. For mosaicism validation, thirteen different trisomic cell lines were mixed in 10% ratio increments with 15 different monosomic cell lines. Main results and the role of chance Amplified samples exhibited distinct separation in ploidy scores between diploidy (PS of 0.91 to 1.85), and triploidy samples (PS of 0.28 to 0.61) with no overlap of boxplots. Specificity, sensitivity, and accuracy were 100%. For mosaicism validation, mixing different ratios of cell lines featuring monosomy and cell lines for a trisomy for different chromosomes resulted in ratios of monosomy: disomy for one chromosome and trisomy: disomy for the other. We assessed 32 combinations of cell lines, each one in 10% increments of each cell line from 0:100% to 100%:0%. Mixes with 40% trisomy mosaicism exhibited a 2.35 median ploidy, while 50%, 60%, 70% and 80% mixes show 2.45, 2.50, 2.60, and 2.70, respectively. Mixes with 40% monosomy mosaicism exhibited a median ploidy of 1.6, while 50%, 60%, 70% and 80% mixes showed 1.50, 1.45, 1.35, and 1.25, respectively. The literature recommends considering <40% mosaicism as euploid and 80-100% as aneuploid, therefore, ploidy scores below 2.35 are deemed euploid, ploidy scores at or above 2.35, but below 2.6 (40%-60%), are classified as low level mosaic, and ploidy scores equal to or above 2.6, but below 2.7, are classified as high mosaic. Embryos equal to or above 2.8 (80%+) are considered aneuploid. Limitations, reasons for caution This test is not designed to screen for tetraploidy (92 XXYY) and has not undergone validation for it nor haploidy. Validation procedures solely utilized cell lines. Reanalysis of the remainder of embryos deemed triploid or high-rate mosaic using this validation results are currently underway. Wider implications of the findings This Previda Plus platform combined with proprietary chemistry provides a rapid, cost effective, and a streamlined workflow for aneuploidy, triploidy, and mosaicism for use in PGT-A of blastocysts biopsies. Trial registration number not applicable

P-408 Monozygotic twins from in vitro fertilization: can bring the rate closer to that of natural conception?

Abstract Study question Whether the occurrence of monozygotic twins in human in vitro fertilization is associated with zona manipulations, and can we explore approaches to reduce its rates? Summary answer Monozygotic twinning is partially caused by zona manipulation, and it can be lowered by creating a larger opening in the zona before embryo transfer. What is known already While the rate of monozygotic twins in spontaneous conception is 0.5% of live births, the frequency of monozygotic twins after in vitro fertilization-embryo transfer can be a few times higher. Various factors have been suggested to contribute to this phenomenon, including ovarian stimulation, intracytoplasmic sperm injection, embryo cryopreservation, extended culture, embryo quality, maternal age, genetic factors, and micromanipulation of the zona pellucida, such as assisted hatching and biopsy. Due to the fact that the overall rate is low, it is difficult to pinpoint the main reason(s) contributing to it, and there are no effective approach(es) to lower this rate. Study design, size, duration We studied monozygotic twins in 8,063 clinical pregnancies resulting from single blastocyst transfers from 2016 to 2023. Blastocysts, whether fresh or frozen, were transferred with or without biopsy for preimplantation genetic testing and/or blastocyst collapse. Clinical pregnancy, embryo implantation, including twin implantation, and clinical outcomes such as live birth, ongoing pregnancy, and birth weight were further evaluated. Monozygotic twin rates were compared between partial zona removal (larger hole) and no zona removal (small hole) Participants/materials, setting, methods Monozygotic twins were initially evaluated in blastocysts with or without biopsy in 732 clinical pregnancies after fresh or frozen embryo transfer. Subsequently, monozygotic twins were further evaluated in 7331 clinical pregnancies after an approach to open a larger hole in the zona before blastocyst transfer. Additionally, 56 monozygotic twins were evaluated for live birth and birth weight outcomes. Main results and the role of chance In the context of fresh blastocyst transfer, the monozygotic twin rate following biopsy was significantly higher than that for blastocysts that did not undergo zona manipulation (3.4% vs. 0.29%; p = 0.025). After blastocysts underwent biopsy and cryopreservation/warming, the monozygotic twin rate was 2.79%, a similar rate as observed in fresh blastocyst transfer after biopsy. However, when frozen blastocysts (either biopsied and/or collapsed) underwent partial zona removal before transfer, the rate of monozygotic twins significantly decreased to 0.6% (p = 0.00001). When we further examined whether the biopsy procedure increased the monozygotic twin rate (28/4947) under the conditions that partial zona removal was performed by comparing those with blastocysts without biopsy (16/2384), we did not find a significant difference (0.57% vs. 0.67%, p = 0.587) between the two treatments. In this study, there were 34 twin live births (60.7%) including 5 ongoing twin pregnancies, and 9 (16.1%) singleton live births, contributing to an overall live birth rate of 76.8%. Ten cases (17.8%) experienced pregnancy loss with heartbeat cessation during the first trimester. Furthermore, 3 cases (5.4%) had abnormal pregnancies. When the birth weights were evaluated among the monozygotic twins, it was found that lower birth weight (< 1500g) was only observed in twin live birth. Limitations, reasons for caution This study only included data from one large clinic in the US under the conditions and protocols (embryo culture, embryo biopsy, and cryopreservation) used in this clinic. Different patients and protocols would affect the rate differently. Wider implications of the findings Zona manipulations are associated with an increased monozygotic twin rate in both fresh and frozen embryo transfers. This effect can be mitigated by creating a larger opening in the zona before embryo transfer, and this approach can bring the monozygotic twin rate closer to that of natural conception. Trial registration number NA

P-504 Examining the success rates following a second embryo biopsy for inconclusive results in preimplantation genetic testing for monogenic diseases (PGT-M): a matched case-control study

Abstract Study question Can an embryo re-biopsy for a previous inconclusive result influence clinical pregnancy compared to a successful PGT-M diagnosis from the first biopsy? Summary answer The embryo re-biopsy intervention for PGT-M seems to reduce the implantation potential of a blastocyst. What is known already PGT-M allows embryo genetic profiling prior to transfer in couples with hereditary genetic disorders, as part of in vitro fertilization process. The need of a trophectoderm biopsy for the retrieval of a fragment of about 8-10 blastomeres is generally sufficient for optimal DNA amplification and molecular analysis. However, a proportion of embryos (approximately 10-12%) fails to be properly diagnosed after PGT-M testing due to inconclusive results. Therefore, as an attempt to obtain a genetic diagnosis, the embryo biopsy can be repeated on the same embryos although retesting involves a second round of biopsy and a second round of vitrification. Study design, size, duration Twenty-seven embryos from women undergoing PGT-M at an infertility center and transferred after two biopsies for genetic analysis were matched for age, fertility status, and study period, to embryos transferred after a conclusive PGT-M result after the first biopsy. The main outcome was the clinical pregnancy rate following embryo transfers in cases in whom embryos had a single biopsy, and when a re-biopsy was performed. The secondary outcome was the live birth rate. Participants/materials, setting, methods Ovarian stimulation, oocyte collection and fertilization were performed according to standard protocols. Embryos were cultured to blastocyst stage in groups of up to five, using one-step media. Blastocysts were biopsied on day 5, 6, or 7, employing either the pulling or flicking method based on their appearance. Biopsied cells were stored at -20 °C for genetic analysis. Vitrification was performed using Kitazato protocol. If results were inconclusive, a second biopsy was performed in surviving blastocysts. Main results and the role of chance The median [interquartile range] number of retrieved and injected oocytes was similar between the two groups, as well as fertilization rate and number of blastocysts obtained. No difference between the two groups was also observed pertaining to the day of embryo culture in which the first biopsy was performed. Conversely, the number of non-diagnosticated and transferable blastocysts was lower in patients whose blastocysts were re-biopsied. In 90% of the re-biopsies an informative result was obtained. Clinical pregnancy rate was 52% (95% CI: 34-69) following the transfer of a single-biopsy blastocyst and 30% (95% CI: 16-48) following the transfer of a re-biopsied blastocyst. The likelihood to have a healthy baby was 33% (95% CI: 19-52) following the transfer of a blastocyst biopsied once and 22% (95% CI: 11-41) following the transfer of a re-biopsied blastocyst. Limitations, reasons for caution The matching design, which aligns women’s age and fertility status in the two groups, allowed the assessment of pregnancy rates while avoiding potential confounding factors associated with retrospective analysis. Given that it is the first study with this design, a larger sample size is necessary to further elucidate these findings. Wider implications of the findings Despite the limited sample size, these results are of extreme clinical relevance. They offer valuable insights for guiding decisions about embryos with unclear results, contributing to the improvement of strategies for selecting those with the highest probability of pregnancy. Trial registration number not applicable

O-270 Clinical-grade whole genome sequencing-based haplarithmisis enables all forms of preimplantation genetic testing

Abstract Study question Can a simple, and scalable assay be developed to concurrently perform all forms of preimplantation genetic testing (PGT), effectively addressing the increasing demand? Summary answer Whole genome sequencing-based haplarithmisis offers a single-assay solution for all forms of PGT, enhancing resolution and diagnosis in complex cases. What is known already State-of-the-art preimplantation genetic testing (PGT) methods, including genotyping-by-sequencing (GBS)-based haplotyping, enable PGT for monogenic disorders (PGT-M), structural rearrangements (PGT-SR), and aneuploidies (PGT-A) in a single assay. However, they are labour intensive, only partially cover the genome, require a close relative to determine meiotic and mitotic origin of aneuploidies, and are troublesome for consanguineous families and in complex genomic contexts. Furthermore, the prevailing PGT approach for mitochondrial DNA disorders (PGT-MT) involves a PCR-based method. This underscores the need to develop a universal PGT method that streamlines laboratory protocols and provides genome-wide coverage to address genetic disorders, even in complex genomic loci. Study design, size, duration In a retrospective pilot study, we compared whole genome sequencing (WGS) at 30-40X with GBS (6 embryos, 2 families, 3 indications). We carried out subsampling of WGS data and determined 10X as the optimal diagnostic depth-of-coverage. We clinically validated our approach by comparing WGS to GBS for PGT-M and PGT-SR (31 embryos, 16 families, 22 indications), to shallow sequencing for PGT-SR (10 embryos, 3 families) and to PCR-based PGT for PGT-MT (10 embryos, 2 families). Participants/materials, setting, methods DNA from parents and close relative(s) and whole genome amplified (WGAed) DNA from embryos, underwent WGS with subsequent haplarithmisis. Quality metrics, such as Mendelian inconsistency rates, number of informative SNPs, and haplotype concordance were assessed. Translocation breakpoints were identified utilizing aberrantly aligned paired sequencing reads. Additionally, single-nucleotide variants (SNVs), including mitochondrial DNA SNVs, were detected by allele counting. Finally, segregational origin was determined via a parents-only haplarithmisis approach that uses the embryo as phasing reference. Main results and the role of chance WGS-PGT alleviates technical limitations by decreasing WGA artifacts by 68.4%, increasing breadth of coverage by 4-fold, and decreasing wet-lab turnaround time by 2.5-fold. Owing to its inherent higher resolution and improved genomic coverage, 5 out of 13 – previously inconclusive – embryos with genetic disorders in complex genomic regions could be assigned a diagnosis. Furthermore, we show the ability to directly detect single- and few-base pair genetic variants in any region of interest. Importantly, we show trio-based PGT-A for aneuploidy origin, an approach we term PGT-AO that – using the parents-only genotype calls – can detect the segregational origin of aneuploidies without the need of a close relative as reference for phasing. The segregational origin detected by parents-only haplarithmisis was concordant with the segregational origin determined from haplarithmisis when using a close relative. Unbalanced translocations could be detected indirectly via haplotyping or directly at single base resolution using a structural variant caller. Mitochondrial heteroplasmy level calculation from WGS yielded comparable results to PCR-based methods, both in blastomere and trophectoderm biopsy samples. Limitations, reasons for caution Direct variant detection with an average coverage of 10X may occasionally be inadequate, as certain locations may lack sufficient coverage (<5 reads). Inherently to the limited sample size of PGT-MT families, WGS-PGT needs further validation. The need for invasive trophectoderm biopsies of preimplantation embryos remains the key limitation of WGS-PGT. Wider implications of the findings Our approach enables all forms of PGT in a single assay. Direct variant detection complements haplarithmisis, addressing inconclusive findings and aiding families with a de novo variant or lacking a close relative for phasing. Finally, PGT-AO facilitates research on the origin of aneuploidies in preimplantation embryos and their clinical outcome. Trial registration number not applicable

P-175 Morphokinetic growth variance score as a tool to identify euploid embryos with the highest live birth potential

Abstract Study question Is the longitudinal growth pattern of euploid embryos associated with live birth rate? Summary answer Embryos with lower growth variance score (GVS), i.e., pointing towards a steadier growth during time-lapse monitoring (TLM), have higher live birth rates. What is known already Dynamic TLM imaging has been increasingly adopted by fertility clinics as an attempt to improve the ability of selecting embryos with the highest potential for implantation. Many authors have identified and incorporated markers of embryonic morphokinetics into decision algorithms for embryo (de)selection. However, longitudinal changes during this temporal process, and the impact of such changes on embryonic competence remains unknown. Aiming to model the reference ranges of euploid embryonic growth as a single growth trajectory might provide an additive value to blastocyst morphological grade to identify highly competent euploid embryos. Study design, size, duration This observational cohort study was performed in a tertiary referral IVF centre between October 2017 and June 2021, including a total of 340 single euploid autologous frozen embryo transfers. Pre-implantation genetic diagnosis for aneuploidy (PGT-A) performed by next generation sequency (NGS). Pregnancy outcomes were assessed as live birth, pregnancy loss or not pregnant. Participants/materials, setting, methods Standard morphokinetic parameters (tPB2 to tEB) of all euploid embryos cultured in TLM system were used to develop the reference ranges for the growth variance score (GVS) model. Nuclear errors at two- and four-cell stages, and blastocyst grade before trophectoderm (TE)-biopsy were also annotated. GVS of euploid embryos was evaluated for its association with pregnancy outcomes, and to its predictive ability to live birth potential over TE and inner cell mass (ICM) grade morphology. Main results and the role of chance A total of 189 (55.6%) euploid transfers resulted in a live birth, 48 (14.1%) in pregnancy loss and 103 (30. 3%) did not result in pregnancy. The median time for euploid embryo blastulation was 109.9 hours (95% CI:98.8-121.0 hours). Lower quality ICM (OR: 0.13, 95% CI: 0.05-0.33, P < 0.001) and TE (OR: 0.46, 95% CI:0.22-0.94, P = 0.034), multinucleation at 4-cell stage (OR: 0.042, 95% CI:0.21-0.84, P = 0.016) and higher GVS (OR: 0.59, 95% CI: 0.45-0.77, P < 0.001), significantly decreased the odds of live birth. In the multivariable analysis, only GVS (OR: 0.62, 95% CI: 0.46-0.84, P = 0.002) and lower ICM quality (OR: 0.21, 95% CI: 0.06-0.65, P = 0.009) had a significant effect on live birth. There was a significant trend towards higher live birth rates with lower GVS among embryos of similar ICM grades: 85% vs 65% live births in low vs. high GVS for embryos with ICM type A, 76% vs. 48% for ICM type B, 67% vs. 21% for ICM type C, respectively (P for trend <0.001). Addition of the GVS to embryo morphology model (ICM, TE, biopsy day) significantly improved the model’s ability to predict live birth (AUC: 0.67 vs. 0.62, P = 0.015). Limitations, reasons for caution The exclusion of IVF cases limits the utility of the model to ICSI-derived embryos. The utility of GVS should be replicated further in external cohorts to confirm its reproducibility in other clinical and laboratory settings. Wider implications of the findings By capturing the dynamic growth pattern of embryos, GVS may serve as a valuable tool in prioritizing PGT-A tested embryos for transfer. Its impact was even more prominent for selecting suboptimal blastocysts, which is a more challenging subset of embryos to choose due to their likelihood of reduced viability. Trial registration number Not Applicable

O-273 A transcriptomic approach for embryo selection after preimplantation genetic diagnosis for aneuploidy

Abstract Study question Is it possible to predict an euploid chromosomal constitution from RNA-Seq data and identify a transcriptomic profile compatible with extended embryonic development? Summary answer It has been possible to obtain a karyotype comparable to PGT-A, in addition to acquiring a transcriptomic signature of embryos suggestive of improved implantation capacity What is known already Conventional assessment of embryo competence, based on morphology and morphokinetic, lacks knowledge of molecular aspects and faces controversy in predicting ploidy status. Understanding the embryonic transcriptome is crucial, as gene expression influences development and implantation. Preimplantation genetic testing (PGT) has improved pregnancy rates, but problems persist when high-quality euploid embryos do not reach term. In fact, around 50 to 60% implant, of which 10% miscarry. Comprehensive approaches, including RNA-Seq, offer potential to discover molecular markers of reproductive competence. Extended-embryo culture platforms up to day 14 can be utilized as a proxy to study embryo development at post-implantation stages Study design, size, duration Prospective pilot cohort study conducted from March 2023 to August 2023. A total of 30 vitrified human blastocysts with previous PGT-A diagnosis on day 5 (D5) or day 6 (D6) of development were analysed: n = 15 euploid and n = 15 aneuploid embryos. Finally, 21 embryo samples were included in the study (n = 10 euploid and n = 11 aneuploid), the rest (n = 9) were excluded due to poor quality after sequencing. All embryos were donated for research purposes Participants/materials, setting, methods Following warming and re-expansion, embryos underwent a second trophectoderm biopsy. The remaining embryo was cultured until day 11 to assess its development. After biopsy analysis by RNA-Seq, karyotypes were studied, as well as differential expression gene (DEG) of the comparison: unattached embryos (n = 12) vs embryos attached (n = 9) to the plate (padj<0.05 and FC > 1). In addition, we obtained a transcriptomic signature specific to embryos with a “theoretical” capacity for sustained implantation (raw p-value<0.05 and shrunk LFC>1.1) Main results and the role of chance Digital karyotype concordance was obtained with a sensitivity of 81%, a specificity of 83%, a Kappa index of 65.5% and an area under the ROC curve of 90%. At the gene level, 76 DEGs (56 upregulated and 20 downregulated) were found in the comparison of embryos unattached to the plate in extended culture versus those that were attached. To address the functional implications of these differences, significantly deregulated pathways according to GO and KEGG categories were identified. The mural trophectoderm of the analysed blastocysts showed 63 significantly deregulated terms (30 GO-Biological Process, 13 GO-Cellular Component, 12 GO-Molecular Function and 8 KEGG pathways), displaying upregulation of autophagy, apoptosis, protein kinase and ubiquitin-like protein ligase activity, and downregulation of ribosome, spliceosome, kinetochore, segregation, and chromosome condensation processes. The first described transcriptomic signature specific to embryos with theoretical enhanced implantation capacity consists of 501 genes, including: EMP2, AURKB, FOLR1, NOTCH3, LRP2, FZD5, MDH1, APOD, GPX8, COLEC12, HSPA1A, CMTM7, BEX3, which are related to implantation and embryonic development. These findings indicate that it would be possible to identify euploid embryos with a greater capacity for implantation and development, excluding those embryos that, although they could be implanted and viable, present chromosomal alterations Limitations, reasons for caution This study included a small sample size and a remarkable variability between samples. Structural chromosomal abnormalities were not included. It is not possible to diagnose mosaic embryos. Trophectoderm biopsy does not assure the chromosomal status of the whole embryo. Maximum number of days for in vitro development was 11 Wider implications of the findings Gene expression profiles of embryos with theoretical increased implantation capacity have been obtained. Clinical implementation of this technique, which assesses chromosomal content and transcriptomic profile, could be used to significantly increase clinical outcomes in assisted reproduction, allowing informed decisions to be made about future treatments and the prospects of success Trial registration number Not applicable

P-554 Artificial intelligence (AI) for embryo genetic risk assessment: a novel form of preimplantation genetic screening

Abstract Study question Can an AI-based embryo ploidy screening tool effectively provide a genetic risk assessment on Day 5 embryos? Summary answer AI screening results showed strong predictive value for early detection of at-risk embryos warranting confirmatory diagnostic testing, based only on time lapse video assessment. What is known already Euploid embryo transfer is the dogma of IVF success. Embryo evaluation relies extensively on diagnostic preimplantation genetic testing for aneuploidy (PGT-A) by means of trophectoderm biopsy. Though pivotal, this presents substantial practical and financial limitations. There is demand for an alternative genetic screening method that provides a quantitative embryo genetic risk assessment for patients who opt out of invasive diagnostic testing, or who intend to undergo fresh transfer. These results can provide information for understanding your aneuploidy risk for more precise prognosis counseling and testing. This is important since diagnostic tests may incur excess financial burden, inconclusive outcomes, and time-to-results. Study design, size, duration Time lapse videos (N = 5,000) were used for AI training. The AI core architecture was a video transformer model for spatio-temporal video sampling. Known ploidy and live-birth results were used as ground truth, with maternal age and embryo quality scores incorporated as input parameters during calibrated logistic regression. A blind test dataset (N = 708 embryos; euploid=352; aneuploid=356; mean ± SD patient age: 35.9 ± 5.4 years) was used to evaluate predictive accuracy. Participants/materials, setting, methods The AI outputs a scalar (1-99) that associates with euploidy likelihood. The AI’s screening value was determined by its specificity (correct prediction of aneuploid), sensitivity (correct prediction of euploid), false positive, and false negative rate. We determined optimal AI score thresholds that identified high aneuploidy and euploidy risk categories (AI score <33; AI score >66, respectively). Main results and the role of chance Specificity of the AI screening test was 83.0%, with a sensitivity of 56.0%. The false positive rate was 26.7% and the false negative rate was 29.3%. The AI’s high specificity relative to its sensitivity shows its clinical value to deselect embryos with the strongest risk of genetic abnormality, and for the prioritization of embryos for confirmatory PGT. Boxplot visualization of the full AI score distribution showed successful discrimination between aneuploid and euploid embryos (mean AI score for aneuploid and euploid were 51.3 and 43.5, respectively) with appropriately minimized overlapping of the interquartile range. The optimal AI score thresholds for detecting embryos with the highest and lowest likelihoods of euploidy were >66 /<33, respectively, representing 71% likelihood of euploidy for the >66 group and 72% aneuploidy for the <33 group. Limitations, reasons for caution The screening does not provide diagnostic genetic testing on the chromosome level. The influence of mosaicism on the false positive/negative rates was not assessed. Wider implications of the findings Results support the use of an AI ploidy screening test for effective decision-making and triage of at-risk embryos for transfer or confirmatory diagnostic testing via PGT-A. Trial registration number Not applicable

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<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<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