The human periconceptional maternal-embryonic space in health and disease.

Pregnancy is established during the periconceptional period as a continuum beginning with blastocyst attachment to the endometrial epithelial surface followed by embryo invasion and placenta formation. This period sets the foundation for the child and mother's health during pregnancy. Emerging evidence indicates that prevention of downstream pathologies in both the embryo/newborn and pregnant mother may be possible at this stage. In this review, we discuss current advances in the periconceptional space, including the preimplantation human embryo and maternal endometrium. We also discuss the role of the maternal decidua, the periconceptional maternal-embryonic interface, the dialogue between these elements, and the importance of the endometrial microbiome in the implantation process and pregnancy. Finally, we discuss the myometrium in the periconceptional space and review its role in determining pregnancy health.

On the reproductive capabilities of aneuploid human preimplantation embryos.

In IVF cycles, the application of aneuploidy testing at the blastocyst stage is quickly growing, and the latest reports estimate almost half of cycles in the US undergo preimplantation genetic testing for aneuploidies (PGT-A). Following PGT-A cycles, understanding the predictive value of an aneuploidy result is paramount for making informed decisions about the embryo's fate and utilization. Compelling evidence from non-selection trials strongly supports that embryos diagnosed with a uniform whole-chromosome aneuploidy very rarely result in the live birth of a healthy baby, while their transfer exposes women to significant risks of miscarriage and chromosomally abnormal pregnancy. On the other hand, embryos displaying low range mosaicism for whole chromosomes have shown reproductive capabilities somewhat equivalent to uniformly euploid embryos, and they have comparable clinical outcomes and gestational risks. Therefore, given their clearly distinct biological origin and clinical consequences, careful differentiation between uniform and mosaic aneuploidy is critical in both the clinical setting when counseling individuals and in the research setting when presenting aneuploidy studies in human embryology. Here, we focus on the evidence gathered so far on PGT-A diagnostic predictive values and reproductive outcomes observed across the broad spectrum of whole-chromosome aneuploidies detected at the blastocyst stage to obtain evidence-based conclusions on the clinical management of aneuploid embryos in the quickly growing PGT-A clinical setting.

Mosaic human preimplantation embryos and their developmental potential in a prospective, non-selection clinical trial.

Chromosome imbalance (aneuploidy) is the major cause of pregnancy loss and congenital disorders in humans. Analyses of small biopsies from human embryos suggest that aneuploidy commonly originates during early divisions, resulting in mosaicism. However, the developmental potential of mosaic embryos remains unclear. We followed the distribution of aneuploid chromosomes across 73 unselected preimplantation embryos and 365 biopsies, sampled from four multifocal trophectoderm (TE) samples and the inner cell mass (ICM). When mosaicism impacted fewer than 50% of cells in one TE biopsy (low-medium mosaicism), only 1% of aneuploidies affected other portions of the embryo. A double-blinded prospective non-selection trial (NCT03673592) showed equivalent live-birth rates and miscarriage rates across 484 euploid, 282 low-grade mosaic, and 131 medium-grade mosaic embryos. No instances of mosaicism or uniparental disomy were detected in the ensuing pregnancies or newborns, and obstetrical and neonatal outcomes were similar between the study groups. Thus, low-medium mosaicism in the trophectoderm mostly arises after TE and ICM differentiation, and such embryos have equivalent developmental potential as fully euploid ones.

An expert opinion on rescuing atypically pronucleated human zygotes by molecular genetic fertilization checks in IVF.

IVF laboratories routinely adopt morphological pronuclear assessment at the zygote stage to identify abnormally fertilized embryos deemed unsuitable for clinical use. In essence, this is a pseudo-genetic test for ploidy motivated by the notion that biparental diploidy is required for normal human life and abnormal ploidy will lead to either failed implantation, miscarriage, or significant pregnancy complications, including molar pregnancy and chorionic carcinoma. Here, we review the literature associated with ploidy assessment of human embryos derived from zygotes displaying a pronuclear configuration other than the canonical two, and the related pregnancy outcome following transfer. We highlight that pronuclear assessment, although associated with aberrant ploidy outcomes, has a low specificity in the prediction of abnormal ploidy status in the developing embryo, while embryos deemed abnormally fertilized can yield healthy pregnancies. Therefore, this universal strategy of pronuclear assessment invariably leads to incorrect classification of over 50% of blastocysts derived from atypically pronucleated zygotes, and the systematic disposal of potentially viable embryos in IVF. To overcome this limitation of current practice, we discuss the new preimplantation genetic testing technologies that enable accurate identification of the ploidy status of preimplantation embryos and suggest a progress from morphology-based checks to molecular fertilization check as the new gold standard. This alternative molecular fertilization checking represents a possible non-incremental and controversy-free improvement to live birth rates in IVF as it adds to the pool of viable embryos available for transfer. This is especially important for the purposes of 'family building' or for poor-prognosis IVF patients where embryo numbers are often limited.

An ESHG-ESHRE survey on the current practice of expanded carrier screening in medically assisted reproduction.

STUDY QUESTION: What is the current practice and views on (expanded) carrier screening ((E)CS) among healthcare professionals in medically assisted reproductive (MAR) practices in Europe? SUMMARY ANSWER: The findings show a limited support for ECS with less than half of the respondents affiliated to centres offering ECS, and substantial variation in practice between centres in Europe. WHAT IS KNOWN ALREADY: The availability of next-generation sequencing, which enables testing for large groups of genes simultaneously, has facilitated the introduction and expansion of ECS strategies, currently offered particularly in the private sector in the context of assisted reproduction. STUDY DESIGN, SIZE, DURATION: A cross-sectional survey evaluating practice and current views among professionals working in MAR practice in different European countries was designed using the online SurveyMonkey tool. The web-based questionnaire included questions on general information regarding the current practice of (E)CS in MAR and questions on what is offered, to whom the test is offered, and how it is offered. It consisted mostly of multiple-choice questions with comment boxes, but also included open questions on the respondents' attitudes/concerns relevant to (E)CS practice, and room to upload requested files (e.g. guidelines and gene panels). In total, 338 responses were collected from 8 February 2022 to 11 April 2022. PARTICIPANTS/MATERIALS, SETTING, METHODS: The online survey was launched with an invitation email from the ESHRE central office (n = 4889 emails delivered) and the European Society of Human Genetics (ESHG) central office (n = 1790 emails delivered) sent to the ESHRE and ESHG members, and by social media posts. The survey was addressed to European MAR centres or gamete banks and to centres located in non-European countries participating in the European IVF-monitoring Consortium. Two reminder emails were sent. After exclusion of 39 incomplete responses received (e.g. only background information), 299 respondents from 40 different countries were included for analyses. MAIN RESULTS AND THE ROLE OF CHANCE: Overall, 42.5% (127/299) of respondents were affiliated to centres offering ECS. The perceived responsibility to enable prospective parents to make informed reproductive decisions and preventing suffering/burden for parents were the main reasons to offer ECS. A single ECS panel is offered by nearly 45% (39/87 received answers) of the centres offering ECS, 25.3% (22/87) of those centres offer a selection of ECS panels, and 29.9% (26/87) offer whole exome sequencing and a large in silico panel. Different ranges of panel sizes and conditions were included in the ECS panel(s) offered. Most of the respondents (81.8%; 72/88 received answers) indicated that the panels they offer are universal and target the entire population. Pathogenic variants (89.7%; 70/78 received answers), and to a lesser extent, likely pathogenic variants (64.1%%; 50/78 received answers), were included in the ECS report for individuals and couples undergoing MAR with their own gametes. According to 87.9% (80/91 received answers) of the respondents, patients have to pay to undergo an ECS test. Most respondents (76.2%; 61/80 received answers) reported that counselling is provided before and after the ECS test. Preimplantation genetic testing, the use of donor gametes, and prenatal diagnostic testing were the three main reproductive options discussed with identified carrier couples. The main reason, according to the respondents, for not offering ECS in their centre, was the lack of professional recommendations supporting ECS (52.5%; 73/139 received answers) and the high cost for couples or reimbursement not being available (49.6%; 69/139). The challenges and moral dilemmas encountered by the respondents revolved mainly around the content of the offer, including the variants classification and the heterogeneity of the panels, the counselling, and the cost of the test. LIMITATIONS, REASONS FOR CAUTION: Although the total number of respondents was acceptable, the completion rate of the survey was suboptimal. In addition, the heterogeneity of answers to open-ended questions and the ambiguity of some of the answers, along with incomplete responses, posed a challenge in interpreting survey results. It is also plausible that some questions were not easily understood by the respondents. For this reason, response and non-response bias are acknowledged as further limitations of the survey. WIDER IMPLICATIONS OF THE FINDINGS: The results of this survey could aid in identifying potential challenges or areas for improvement in the current practice of ECS in the MAR field and contribute to the discussion on how to address them. The results underline the need to stimulate a more knowledge-based debate on the complexity and the pros and cons of a possible implementation of ECS in MAR. STUDY FUNDING/COMPETING INTEREST(S): All costs relating to the development process were covered from European Society of Human Reproduction and Embryology and European Society of Human Genetics funds. There was no external funding of the development process or manuscript production. A.C. is full-time employee of Juno Genetics. L.H. declared receiving a research grant during the past 36 months from the Netherlands Organisation for Health Research and Development. She has also participated in a Health Council report of the Netherlands on preconception carrier screening and collaborated with the VSOP Dutch Genetic Alliance (patient umbrella organization on rare and genetic disorders). L.H. and C.v.E. are affiliated with Amsterdam University Medical Centre, a hospital that offers ECS in a non-commercial setting. R.V. received honoraria for presentations from Merck Academy and is unpaid board member of the executive committee of the Spanish Fertility Society. The other authors had nothing to disclose. TRIAL REGISTRATION NUMBER: N/A.

Incidence, Origin, and Predictive Model for the Detection and Clinical Management of Segmental Aneuploidies in Human Embryos.

Despite next-generation sequencing, which now allows for the accurate detection of segmental aneuploidies from in vitro fertilization embryo biopsies, the origin and characteristics of these aneuploidies are still relatively unknown. Using a multifocal biopsy approach (four trophectoderms [TEs] and one inner cell mass [ICM] analyzed per blastocyst; n = 390), we determine the origin of the aneuploidy and the diagnostic predictive value of segmental aneuploidy detection in TE biopsies toward the ICM's chromosomal constitution. Contrary to the prevalent meiotic origin of whole-chromosome aneuploidies, we show that sub-chromosomal abnormalities in human blastocysts arise from mitotic errors in around 70% of cases. As a consequence, the positive-predictive value toward ICM configuration was significantly lower for segmental as compared to whole-chromosome aneuploidies (70.8% versus 97.18%, respectively). In order to enhance the clinical utility of reporting segmental findings in clinical TE biopsies, we have developed and clinically verified a risk stratification model based on a second TE biopsy confirmation and segmental length; this model can significantly improve the prediction of aneuploidy risk in the ICM in over 86% of clinical cases enrolled. In conclusion, we provide evidence of the predominant mitotic origin of segmental aneuploidies in preimplantation embryos and develop a risk stratification model that can help post-test genetic counseling and that facilitates the decision-making process on clinical utilization of these embryos.

Implementing preconception expanded carrier screening in a universal health care system: A model-based cost-effectiveness analysis.

PURPOSE: The limited evidence available on the cost-effectiveness (CE) of expanded carrier screening (ECS) prevents its widespread use in most countries, including Italy. Herein, we aimed to estimate the CE of 3 ECS panels (ie, American College of Medical Genetics and Genomics [ACMG] Tier 1 screening, "Focused Screening," testing 15 severe, highly penetrant conditions, and ACMG Tier 3 screening) compared with no screening, the health care model currently adopted in Italy. METHODS: The reference population consisted of Italian couples seeking pregnancy with no increased personal/familial genetic risk. The CE model was developed from the perspective of the Italian universal health care system and was based on the following assumptions: 100% sensitivity of investigated screening strategies, 77% intervention rate of at-risk couples (ARCs), and no risk to conceive an affected child by risk-averse couples opting for medical interventions. RESULTS: The incremental CE ratios generated by comparing each genetic screening panel with no screening were: -14,875 ± 1,208 €/life years gained (LYG) for ACMG1S, -106,863 ± 2,379 €/LYG for Focused Screening, and -47,277 ± 1,430 €/LYG for ACMG3S. ACMG1S and Focused Screening were dominated by ACMG3S. The parameter uncertainty did not significantly affect the outcome of the analyses. CONCLUSION: From a universal health care system perspective, all the 3 ECS panels considered in the study would be more cost-effective than no screening.

Healthy live birth following embryo transfer of a blastocyst of tetrapronuclear (4PN) origin: a case report.

During IVF treatments, normal fertilization is generally evidenced by the appearance of two pronuclei, one arising from the oocyte and the other from the male gamete. Embryos derived from zygotes with a pronuclei number other than two are assumed to possess a ploidy abnormality and their transfer is usually avoided owing to increased risk of implantation failure, miscarriage, and molar pregnancies. Nonetheless, the inclusion of genotyping data in preimplantation genetic testing has revealed that a normal diploid configuration is possible in embryos deriving from zygotes with an abnormal pronuclei number such as tripronuclear and one pronucleus. Here, we present a one-of-a-kind transfer of a tetrapronuclear-derived embryo that was discovered to be diploid and negative for other whole chromosome or segmental aneuploidies during preimplantation genetic testing using a targeted next-generation sequencing approach. The transfer resulted in the live birth of a healthy infant who is now 4 years old and has no apparent health or developmental impairments.

The use of copy number loads to designate mosaicism in blastocyst stage PGT-A cycles: fewer is better.

STUDY QUESTION: How well can whole chromosome copy number analysis from a single trophectoderm (TE) biopsy predict true mosaicism configurations in human blastocysts? SUMMARY ANSWER: When a single TE biopsy is tested, wide mosaicism thresholds (i.e. 20-80% of aneuploid cells) increase false positive calls compared to more stringent ones (i.e. 30-70% of aneuploid cells) without improving true detection rate, while binary classification (aneuploid/euploid) provides the highest diagnostic accuracy. WHAT IS KNOWN ALREADY: Next-generation sequencing-based technologies for preimplantation genetic testing for aneuploidies (PGT-A) allow the identification of intermediate chromosome copy number alterations potentially associated with chromosomal mosaicism in TE biopsies. Most validation studies are based on models mimicking mosaicism, e.g. mixtures of cell lines, and cannot be applied to the clinical interpretation of TE biopsy specimens. STUDY DESIGN, SIZE, DURATION: The accuracy of different mosaicism diagnostic thresholds was assessed by comparing chromosome copy numbers in multiple samples from each blastocyst. Enrolled embryos were donated for research between June 2019 and September 2020. The Institutional Review Board at the Near East University approved the study (project: YDU/2019/70-849). Embryos showing euploid/aneuploid mosaicism (n = 53), uniform chromosomal alterations (single or multiple) (n = 25), or uniform euploidy (n = 39) in their clinical TE biopsy were disaggregated into five portions: the inner cell mass (ICM) and four TE segments. Collectively, 585 samples from 117 embryos were analysed. PARTICIPANTS/MATERIALS, SETTING, METHODS: Donated blastocysts were warmed, allowed to re-expand, and disaggregated in TE portions and ICM. PGT-A analysis was performed using Ion ReproSeq PGS kit and Ion S5 sequencer (ThermoFisher). Sequencing data were blindly analysed with Ion Reporter software to estimate raw chromosome copy numbers. Intra-blastocyst comparison of copy number data was performed employing different thresholds commonly used for mosaicism detection. From copy number data, different case scenarios were created using more stringent (30-70%) or less stringent criteria (20-80%). Categorical variables were compared using the two-sample z test for proportions. MAIN RESULTS AND THE ROLE OF CHANCE: When all the five biopsies from the same embryo were analysed with 30-70% thresholds, only 8.4% (n = 14/166) of patterns abnormal in the original analysis revealed a true mosaic configuration, displaying evidence of reciprocal events (3.6%, n = 6/166) or confirmation in additional biopsies (4.8%, n = 8/166), while most mosaic results (87.3% of total predicted mosaic patterns) remained confined to a single TE specimen. Conversely, uniform whole chromosome aneuploidies (28.3% of total patterns, n = 47/166) were confirmed in all subsequent biopsies in 97.9% of cases (n = 46/47). When 20-80% thresholds were employed (instead of 30-70%), the overall mosaicism rate per biopsy increased from 20.2% (n = 114/565) to 40.2% (n = 227/565). However, the use of a wider threshold range did not contribute to the detection of additional true mosaic patterns, while significantly increasing false positive mosaic patterns from 57.8% to 79.5% (n = 96/166; 95% CI = 49.9-65.4 vs n = 271/341; 95% CI = 74.8-83.6, respectively) (P < 0.00001). Moreover, the shift of the aneuploid cut-off from 70% to 80% of aneuploid cells resulted in mosaicism overcalling in the high range (50-80% of aneuploid cells), impacting the accuracy of uniform aneuploid classification. Parametric analysis of thresholds, based on multifocal analysis, revealed that a binary classification scheme with a single cut-off at a 50% level provided the highest sensitivity and specificity rates. Further analysis on technical noise distribution at the chromosome level revealed a greater impact on smaller chromosomes. LIMITATIONS, REASONS FOR CAUTION: While enrolment of a population enriched in embryos showing intermediate chromosome copy numbers enhanced the evaluation of the mosaicism category compared with random sampling such study population selection is likely to lead to an overall underestimation of PGT-A accuracy compared to a general assessment of unselected clinical samples. This approach involved the analysis of aneuploidy chromosome copy number thresholds at the embryo level; future studies will need to evaluate these criteria in relation to clinical predictive values following embryo transfers for different PGT-A assays. Moreover, the study lacked genotyping-based confirmation analysis. Finally, aneuploid embryos with known meiotic partial deletion/duplication were not included. WIDER IMPLICATIONS OF THE FINDINGS: Current technologies can detect low-intermediate chromosome copy numbers in preimplantation embryos but their identification is poorly correlated with consistent propagation of the anomaly throughout the embryo or with negative clinical consequences when transferred. Therefore, when a single TE biopsy is analysed, diagnosis of chromosomal mosaicism should be evaluated carefully. Indeed, the use of wider mosaicism thresholds (i.e. 20-80%) should be avoided as it reduces the overall PGT-A diagnostic accuracy by increasing the risk of false positive mosaic classification and false negative aneuploid classification. From a clinical perspective, this approach has negative consequences for patients as it leads to the potential deselection of normal embryos for transfer. Moreover, a proportion of uniform aneuploid embryos may be inaccurately categorized as high-level mosaic, with a consequent negative outcome (i.e. miscarriage) when inadvertently selected for transfer. Clinical outcomes following PGT-A are maximized when a 50% threshold is employed as it offers the most accurate diagnostic approach. STUDY FUNDING/COMPETING INTEREST(S): The study was supported by Igenomix. The authors not employed by Igenomix have no conflicts of interest to declare. TRIAL REGISTRATION NUMBER: N/A.

Maternal exome analysis for the diagnosis of oocyte maturation defects and early embryonic developmental arrest.

RESEARCH QUESTION: Can a methodology be developed for case selection and whole-exome sequencing (WES) analysis of women who are infertile owing to recurrent oocyte maturation defects (OOMD) and/or preimplantation embryo lethality (PREMBL)? DESIGN: Data were collected from IVF patients attending the Istanbul Memorial Hospital (2015-2021). A statistical methodology to identify infertile endophenotypes (recurrent low oocyte maturation rate, low fertilization rate and preimplantation developmental arrest) was developed using a large IVF dataset (11,221 couples). Twenty-eight infertile women with OOMD/PREMBL were subsequently enrolled for WES on their genomic DNA. Pathogenic variants were prioritized using a custom-made bioinformatic pipeline set to minimize false-positive discoveries through resampling in control cohorts (the Human Genome Diversity Project and 1343 whole-exome sequences from oocyte donors). Individual single-cell RNA sequencing data from 18 human metaphase II (MII) oocytes and antral granulosa cells was used for genome-wide validation. WES and bioinformatics were performed at Igenomix and the National Research Council, Italy. RESULTS: Variant prioritization analysis identified 265 unique variants in 248 genes (average 22.4 per sample). Of the genes harbouring high-impact variants 78% were expressed by MII oocytes and/or antral granulosa cells, significantly higher than for random sample of controls (odds ratio = 5, Fisher's exact P = 0.0004). Seven of the 28 women (25%) were homozygous carriers of missense pathogenic variants in known candidate genes for OOMD/PREMBL, including PATL2, NLRP5 (n = 2),TLE6, PADI6, TUBB8 and TRIP13. Furthermore, novel gene-disease associations were identified. In fact, one woman with a low oocyte maturation rate was a homozygous carrier of high-impact variants in ENSA, an essential gene for prophase I meiotic transition in mice. CONCLUSIONS: This analytical framework could reveal known and new genes associated with isolated recurrent OOMD/PREMBL, providing essential indications for scaling this strategy to larger studies.

Optimizing clinical exome design and parallel gene-testing for recessive genetic conditions in preconception carrier screening: Translational research genomic data from 14,125 exomes.

Limited translational genomic research data have been reported on the application of exome sequencing and parallel gene testing for preconception carrier screening (PCS). Here, we present individual-level data from a large PCS program in which exome sequencing was routinely performed on either gamete donors (5,845) or infertile patients (8,280) undergoing in vitro fertilization (IVF) treatment without any known family history of inheritable genetic conditions. Individual-level data on pathogenic variants were used to define conditions for PCS based on criteria for severity, penetrance, inheritance pattern, and age of onset. Fetal risk was defined based on actual carrier frequency data accounting for the specific inheritance pattern (fetal disease risk, FDR). In addition, large-scale application of exome sequencing for PCS allowed a deep investigation of the incidence of medically actionable secondary findings in this population. Exome sequencing achieved remarkable clinical sensitivity for reproductive risk of highly penetrant childhood-onset disorders (1/337 conceptions) through analysis of 114 selected gene-condition pairs. A significant contribution to fetal disease risk was observed for rare (carrier rate < 1:100) and X-linked conditions (16.7% and 41.2% of total FDR, respectively). Subgroup analysis of 776 IVF couples identified 37 at increased reproductive risk (4.8%; 95% CI = 3.4-6.5). Further, two additional couples had increased risk for very rare conditions when both members of a parental pair were treated as a unit and the search was extended to the entire exome. About 2.3% of participants showed at least one pathogenic variant for genes included in the updated American College of Medical Genetics and Genomics v2.0 list of secondary findings. Gamete donors and IVF couples showed similar carrier burden for both carrier screening and secondary findings, indicating no causal relationship to fertility. These translational research data will facilitate development of more effective PCS strategies that maximize clinical sensitivity with minimal counterproductive effects.

Epigenetics of pregnancy: looking beyond the DNA code.

Epigenetics is the branch of genetics that studies the different mechanisms that influence gene expression without direct modification of the DNA sequence. An ever-increasing amount of evidence suggests that such regulatory processes may play a pivotal role both in the initiation of pregnancy and in the later processes of embryonic and fetal development, thus determining long-term effects even in adult life. In this narrative review, we summarize the current knowledge on the role of epigenetics in pregnancy, from its most studied and well-known mechanisms to the new frontiers of epigenetic regulation, such as the role of ncRNAs and the effects of the gestational environment on fetal brain development. Epigenetic mechanisms in pregnancy are a dynamic phenomenon that responds both to maternal-fetal and environmental factors, which can influence and modify the embryo-fetal development during the various gestational phases. Therefore, we also recapitulate the effects of the most notable environmental factors that can affect pregnancy and prenatal development, such as maternal nutrition, stress hormones, microbiome, and teratogens, focusing on their ability to cause epigenetic modifications in the gestational environment and ultimately in the fetus. Despite the promising advancements in the knowledge of epigenetics in pregnancy, more experience and data on this topic are still needed. A better understanding of epigenetic regulation in pregnancy could in fact prove valuable towards a better management of both physiological pregnancies and assisted reproduction treatments, other than allowing to better comprehend the origin of multifactorial pathological conditions such as neurodevelopmental disorders.

Considerations on the use of carrier screening testing in human reproduction: comparison between recommendations from the Italian Society of Human Genetics and other international societies.

PURPOSE: Carrier screening (CS) is a term used to describe a genetic test performed on individuals without family history of genetic disorders, to investigate the carrier status for pathogenic variants associated with multiple recessive conditions. The advent of next-generation sequencing enabled simultaneous CS for an increasing number of conditions; however, a consensus on which diseases to include in gene panels and how to best develop the provision of CS is far to be reached. Therefore, the provision of CS is jeopardized and inconsistent and requires solving several important issues. METHODS: In 2020, the Italian Society of Human Genetics (SIGU) established a working group composed of clinical and laboratory geneticists from public and private fields to elaborate a document to define indications and best practice of CS provision for couples planning a pregnancy. RESULTS: Hereby, we present the outcome of the Italian working group's activity and compare it with previously published international recommendations (American College of Medical Genetics and Genomics (ACMG), American College of Obstetricians and Gynecologists (ACOG), and Royal Australian and New Zealand College of Obstetricians and Gynaecologists (RANZCOG)). We determine a core message on genetic counseling and nine main subject categories to explore, spanning from goals and execution to technical scientific, ethical, and socio-economic topics. Moreover, a level of agreement on the most critical points is discussed using a 5-point agreement scale, demonstrating a high level of consensus among the four societies. CONCLUSIONS: This document is intended to provide genetic and healthcare professionals involved in human reproduction with guidance regarding the clinical implementation of CS.

Molecular tools for the genomic assessment of oocyte's reproductive competence.

The most important factor associated with oocytes' developmental competence has been widely identified as the presence of chromosomal abnormalities. However, growing application of genome-wide sequencing (GS) in population diagnostics has enabled the identification of multifactorial genetic predispositions to sub-lethal pathologies, including those affecting IVF outcomes and reproductive fitness. Indeed, GS analysis in families with history of isolated infertility has recently led to the discovery of new genes and variants involved in specific human infertility endophenotypes that impact the availability and the functionality of female gametes by altering unique mechanisms necessary for oocyte maturation and early embryo development. Ongoing advancements in analytical and bioinformatic pipelines for the study of the genetic determinants of oocyte competence may provide the biological evidence required not only for improving the diagnosis of isolated female infertility but also for the development of novel preventive and therapeutic approaches for reproductive failure. Here, we provide an updated discussion and review of the progresses made in preconception genomic medicine in the identification of genetic factors associated with oocyte availability, function, and competence.

Leave the past behind: women's reproductive history shows no association with blastocysts' euploidy and limited association with live birth rates after euploid embryo transfers.

STUDY QUESTION: Is there an association between patients' reproductive history and the mean euploidy rates per biopsied blastocysts (m-ER) or the live birth rates (LBRs) per first single vitrified-warmed euploid blastocyst transfers? SUMMARY ANSWER: Patients' reproductive history (as annotated during counselling) showed no association with the m-ER, but a lower LBR was reported after euploid blastocyst transfer in women with a history of repeated implantation failure (RIF). WHAT IS KNOWN ALREADY: Several studies have investigated the association between the m-ER and (i) patients' basal characteristics, (ii) ovarian stimulation strategy and dosage, (iii) culture media and conditions, and (iv) embryo morphology and day of full blastocyst development. Conversely, the expected m-ER due to women's reproductive history (previous live births (LBs), miscarriages, failed IVF cycles and transfers, and lack of euploid blastocysts among prior cohorts of biopsied embryos) still needs investigations. Yet, this information is critical to counsel new patients about a first cycle with preimplantation genetic testing for aneuploidy (PGT-A), but even more so after former adverse outcomes to prevent treatment drop-out. STUDY DESIGN, SIZE, DURATION: This observational study included all patients undergoing a comprehensive chromosome testing (CCT)-based PGT-A cycle with at least one biopsied blastocyst in the period April 2013-December 2019 at a private IVF clinic (n = 2676 patients undergoing 2676 treatments and producing and 8151 blastocysts). m-ER were investigated according to women's reproductive history of LBs: no/≥1, miscarriages: no/1/>1; failed IVF cycles: no/1/2/>2, and implantation failures after previous transfers: no/1/2/>2. Among the 2676 patients included in this study, 440 (16%) had already undergone PGT-A before the study period; the data from these patients were further clustered according to the presence or absence of euploid embryo(s) in their previous cohort of biopsied blastocysts. The clinical outcomes per first single vitrified-warmed euploid blastocyst transfers (n =1580) were investigated according to the number of patients' previous miscarriages and implantation failures. PARTICIPANTS/MATERIALS, SETTING, METHODS: The procedures involved in this study included ICSI, blastocyst culture, trophectoderm biopsy without hatching in Day 3, CCT-based PGT-A without reporting segmental and/or putative mitotic (or mosaic) aneuploidies and single vitrified-warmed euploid blastocyst transfer. For statistical analysis, Mann-Whitney U or Kruskal-Wallis tests, as well as linear regressions and generalised linear models among ranges of maternal age at oocyte retrieval were performed to identify significant differences for continuous variables. Fisher's exact tests and multivariate logistic regression analyses were instead used for categorical variables. MAIN RESULTS AND THE ROLE OF CHANCE: Maternal age at oocyte retrieval was the only variable significantly associated with the m-ER. We defined five clusters (<35 years: 66 ± 31%; 35-37 years: 58 ± 33%; 38-40 years: 43 ± 35%; 40-42 years: 28 ± 34%; and >42 years: 17 ± 31%) and all analyses were conducted among them. The m-ER did not show any association with the number of previous LBs, miscarriages, failed IVF cycles or implantation failures. Among patients who had already undergone PGT-A before the study period, the m-ER did not associate with the absence (or presence) of euploid blastocysts in their former cohort of biopsied embryos. Regarding clinical outcomes of the first single vitrified-warmed euploid blastocyst transfer, the implantation rate was 51%, the miscarriage rate was 14% and the LBR was 44%. This LBR was independent of the number of previous miscarriages, but showed a decreasing trend depending on the number of previous implantation failures, reaching statistical significance when comparing patients with >2 failures and patients with no prior failure (36% versus 47%, P < 0.01; multivariate-OR adjusted for embryo quality and day of full blastocyst development: 0.64, 95% CI 0.48-0.86, P < 0.01). No such differences were shown for previous miscarriage rates. LIMITATIONS, REASONS FOR CAUTION: The sample size for treatments following a former completed PGT-A cycle should be larger in future studies. The data should be confirmed from a multicentre perspective. The analysis should be performed also in non-PGT cycles and/or including patients who did not produce blastocysts, in order to investigate a putative association between women's reproductive history with outcomes other than euploidy and LBRs. WIDER IMPLICATIONS OF THE FINDINGS: These data are critical to counsel infertile couples before, during and after a PGT-A cycle, especially to prevent treatment discontinuation due to previous adverse reproductive events. Beyond the 'maternal age effect', the causes of idiopathic recurrent pregnancy loss (RPL) and RIF are likely to be endometrial receptivity and selectivity issues; transferring euploid blastocysts might reduce the risk of a further miscarriage, but more information beyond euploidy are required to improve the prognosis in case of RIF. STUDY FUNDING/COMPETING INTEREST(S): No funding was received and there are no competing interests. TRIAL REGISTRATION NUMBER: N/A.

Effects of thyroid hormone on mitochondria and metabolism of human preimplantation embryos.

Thyroid hormones are regarded as the major controllers of metabolic rate and oxygen consumption in mammals. Although it has been demonstrated that thyroid hormone supplementation improves bovine embryo development in vitro, the cellular mechanisms underlying these effects are so far unknown. In this study, we investigated the role of thyroid hormone in development of human preimplantation embryos. Embryos were cultured in the presence or absence of 10-7 M triiodothyronine (T3) till blastocyst stage. Inner cell mass (ICM) and trophectoderm (TE) were separated mechanically and subjected to RNAseq or quantification of mitochondrial DNA copy number. Analyses were performed using DESeq (v1.16.0 on R v3.1.3), MeV4.9 and MitoMiner 4.0v2018 JUN platforms. We found that the exposure of human preimplantation embryos to T3 had a profound impact on nuclear gene transcription only in the cells of ICM (1178 regulated genes-10.5% of 11 196 expressed genes) and almost no effect on cells of TE (38 regulated genes-0.3% of expressed genes). The analyses suggest that T3 induces in ICM a shift in ribosome and oxidative phosphorylation activity, as the upregulated genes are contributing to the composition and organization of the respiratory chain and associated cofactors involved in mitoribosome assembly and stability. Furthermore, a number of genes affecting the citric acid cycle energy production have reduced expression. Our findings might explain why thyroid disorders in women have been associated with reduced fertility and adverse pregnancy outcome. Our data also raise a possibility that supplementation of culture media with T3 may improve outcomes for women undergoing in vitro fertilization.

Technical factors to consider when developing an Expanded Carrier Screening platform.

PURPOSE OF REVIEW: Expanded Carrier Screening (ECS) is a genetic test able to detect carriers for a large number of autosomal recessive and X-linked diseases. Its clinical utilization is increasing but some technical aspects for its implementation are still controversial. RECENT FINDINGS: In the current literature, several aspects of ECS panel implementation have been addressed. One of the most relevant topics involves which genes/pathologies should be included in an optimized ECS panel and which variants should be reported. SUMMARY: Here, we review the best practice criteria to refine and improve clinical utility and validity of an ECS panel. The criteria for optimal ECS panel implementation include the severity of pathologies, the prevalence of diseases in general population and a definitive or strong gene/disease association. Moreover, we discuss the main complications associated with the reporting of Variant of Uncertain Significance and the need for periodic reassessment.

When embryology meets genetics: the definition of developmentally incompetent preimplantation embryos (DIPE)-the consensus of two Italian scientific societies.

A clear definition of developmentally incompetent preimplantation embryo (DIPE) in literature is still missing, while several scientific societies are discussing this challenging topic. From both a clinical and scientific perspective, the identification of embryos unfit for reproductive purpose is crucial. This aim should be pursued in light of all diagnostic technologies for embryo evaluation, encompassing also genetic analyses, of recent implementation in IVF. The Italian context is characterized by an unusual scenario: embryos can be discarded only if not viable and cannot be used for research purposes either. Therefore, thousands of embryos, diagnosed as affected and/or aneuploid as resulting from preimplantation genetic testing (PGT) and clinically not utilizable, are cryopreserved and stored indefinitely, with important psychological, legal, and financial implications. With the aim of updating the definition of DIPE, also on the basis of the embryo genetic status, the Italian Society of Embryology, Reproduction and Research (SIERR) and the Italian Society of Human Genetic (SIGU) reviewed the literature on this topic, found a consensus, and produced a list of relevant criteria.

IUI and uterine lavage of in vivo-produced blastocysts for PGT purposes: is it a technically and ethically reasonable perspective? Is it actually needed?

A recent study by Munné et al. portrayed a protocol to retrieve in vivo produced blastocysts after IUI and uterine lavage for preimplantation genetic testing (PGT) purposes. The authors claimed this protocol might represent a reasonable future perspective for patients who do not want to undergo IVF, but still want to be informed about their embryos' genetic/chromosomal defects. Although the intent of making PGT available also to patients who cannot or do not need to undergo IVF is respectable, the value of this study is undermined by severe technical and ethical issues. Munné and colleagues' paper was discussed within the executive committee (i.e., president and vice-president of the society, director and vice-director of the scientific committee, secretariat, and counselors), the special interest group in reproductive genetics, the scientific committee, and the collegio dei probiviri of the Italian Society of Embryology, Reproduction and Research (SIERR). The points raised from this discussion are summarized in this opinion paper.

Looking past the appearance: a comprehensive description of the clinical contribution of poor-quality blastocysts to increase live birth rates during cycles with aneuploidy testing.

STUDY QUESTION: Which are the clinical benefits and risks of including poor-quality blastocysts (PQBs) in the cohort of biopsied embryos during a cycle with preimplantation genetic testing for aneuploidies (PGT-A)? SUMMARY ANSWER: PQBs show a worse prognosis with respect to sibling non-PQBs, but their clinical use allows an overall 2.6% increase in the number of live births (LBs) achievable after PGT-A. WHAT IS KNOWN ALREADY: PQBs (