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Preimplantation genetic testing (PGT) has emerged as a revolutionary technique in the field of reproductive medicine, allowing for the selection and transfer of healthy embryos, thus reducing the risk of transmitting genetic diseases. However, despite remarkable advancements, the implementation of PGT faces a series of limitations and challenges that require careful consideration. This review aims to foster a comprehensive reflection on the constraints of preimplantation genetic diagnosis, encouraging a broader discussion about its utility and implications. The objective is to inform and guide medical professionals, patients, and society overall in the conscious and responsible adoption of this innovative technology, taking into account its potential benefits and the ethical and practical challenges that it presents.

Purpose The Japan Society of Obstetrics and Gynecology conducted a nationwide clinical study to evaluate the pregnancy outcomes of preimplantation genetic testing for aneuploidy or chromosomal structural rearrangement (PGT‐A/SR). Methods Patients that had experienced recurrent implantation failure, recurrent pregnancy loss, or chromosomal structural rearrangement were recruited from 200 fertility centers in Japan. For patients in whom one or more blastocysts were classified as euploid or euploid with suspected mosaicism, a frozen–thawed single embryo transfer (ET) was performed. Results A total of 10 602 cycles, maternal age 28–50 years, were enrolled in this study. 42 529 blastocysts were biopsied, and 25.5%, 11.7%, and 61.7% of embryos exhibited euploidy, mosaicism, and aneuploidy, respectively. At least one euploid blastocyst was obtained in 38.3% of egg retrieval cycles with embryo biopsy. A total of 6080 ETs were carried out, and the clinical pregnancy rate per ET, ongoing pregnancy rate per ET, and miscarriage rate per pregnancy were 68.8%, 56.3%, and 10.4%, respectively. The rates of clinical pregnancy and miscarriage remained relatively constant across all maternal ages. Conclusions Preimplantation genetic testing for aneuploidy or chromosomal structural rearrangement may improve the pregnancy rate per ET and reduce the miscarriage rate per pregnancy, especially in patients of advanced maternal age.

This document aims to provide good practice recommendations in order to support maternal-foetal medicine specialists, clinical geneticists and clinical laboratory geneticists in the management of pregnancies obtained after the transfer of an embryo tested with preimplantation genetic testing (PGT). It was drafted by geneticists expert in preimplantation genetics and prenatal genetic diagnosis belonging to the “Working Group in Cytogenomics, Prenatal and Reproductive Genetics” of the “Italian Society of Human Genetics” (SIGU). In particular, the paper addresses the diagnostic algorithm to be applied in prenatal follow-up depending on the type of PGT performed, the results obtained and the related diagnostic value based on the most recent literature data and Italian and international recommendations.

There is a high incidence of chromosomal abnormalities in early human embryos, whether they are generated by natural conception or by assisted reproductive technologies (ART). Cells with chromosomal copy number deviations or chromosome structural rearrangements can compromise the viability of embryos; much of the naturally low human fecundity as well as low success rates of ART can be ascribed to these cytogenetic defects. Chromosomal anomalies are also responsible for a large proportion of miscarriages and congenital disorders. There is therefore tremendous value in methods that identify embryos containing chromosomal abnormalities before intrauterine transfer to a patient being treated for infertility—the goal being the exclusion of affected embryos in order to improve clinical outcomes. This is the rationale behind preimplantation genetic testing for aneuploidy (PGT-A) and structural rearrangements (-SR). Contemporary methods are capable of much more than detecting whole chromosome abnormalities (e.g., monosomy/trisomy). Technical enhancements and increased resolution and sensitivity permit the identification of chromosomal mosaicism (embryos containing a mix of normal and abnormal cells), as well as the detection of sub-chromosomal abnormalities such as segmental deletions and duplications. Earlier approaches to screening for chromosomal abnormalities yielded a binary result of normal versus abnormal, but the new refinements in the system call for new categories, each with specific clinical outcomes and nuances for clinical management. This review intends to give an overview of PGT-A and -SR, emphasizing recent advances and areas of active development.

PurposeTo evaluate the use of preimplantation genetic testing (PGT) and live birth rates (LBR) in the USA from 2014 to 2017 and to understand how PGT is being used at a clinic and state level.MethodsThis study accessed SART data for 2014 to 2017 to determine LBR and the CDC for years 2016 and 2017 to identify PGT usage. Primary cycles included only the first embryo transfer within 1 year of an oocyte retrieval; subsequent cycles included transfers occurring after the first transfer or beyond 1 year of oocyte retrieval.ResultsIn the SART data, the number of primary PGT cycles showed a significant monotonic annual increase from 18,805 in 2014 to 54,442 in 2017 (P = 0.042) and subsequent PGT cycles in these years increased from 2946 to 14,361 (P = 0.01). There was a significant difference in primary PGT cycle use by age, where younger women had a greater percentage of PGT treatment cycles than older women. In both PGT and non-PGT cycles, the LBR per oocyte retrieval decreased significantly from 2014 to 2017 (P<0001) and younger women had a significantly higher LBR per oocyte retrieval compared to older women (P < 0.001). The CDC data revealed that in 2016, just 53 (11.4%) clinics used PGT for more than 50% of their cycles, which increased to 99 (21.4%) clinics in 2017 (P< 0.001).ConclusionsA growing number of US clinics are offering PGT to their patients. These findings support re-evaluation of the application for PGT.

Background Preimplantation genetic testing (PGT), also referred to as preimplantation genetic diagnosis (PGD), is an advanced reproductive technology used during in vitro fertilization (IVF) cycles to identify genetic abnormalities in embryos prior to their implantation. PGT is used to screen embryos for chromosomal abnormalities, monogenic disorders, and structural rearrangements. Development of PGT Over the past few decades, PGT has undergone tremendous development, resulting in three primary forms: PGT-A, PGT-M, and PGT-SR. PGT-A is utilized for screening embryos for aneuploidies, PGT-M is used to detect disorders caused by a single gene, and PGT-SR is used to detect chromosomal abnormalities caused by structural rearrangements in the genome. Purpose of Review In this review, we thoroughly summarized and reviewed PGT and discussed its pros and cons down to the minutest aspects. Additionally, recent studies that highlight the advancements of PGT in the current era, including their future perspectives, were reviewed. Conclusions This comprehensive review aims to provide new insights into the understanding of techniques used in PGT, thereby contributing to the field of reproductive genetics.

PurposeTo review cases of couples presented to our PGT-unit with copy number variants (CNVs) classified as variants of uncertain significance (VUS) in order to better understand their needs.MethodsRetrospective cohort study conducted in a tertiary medical-center, 2014–2019. We reviewed files of all couples applying for genetic counseling with CNVs classified as VUS. The main outcomes measured: number of VUS findings and their description, PGT-M procedures planned and performed, IVF cycles, clinical pregnancy, and live birth rates (LBR). VUS were classified according to the American-College of Medical-Genetics and Genomics classification at time of first consultation, and updated—December 2018.ResultsTwenty-four couples presented with a total of 30 VUS. Twelve couples (50%) had isolated VUS and 12 (50%) had VUS diagnosed in addition to a pathogenic mutation. Initially, nine findings (30%) were defined as VUS; eight (27%) as likely benign (b-VUS); and 13 (43%) as likely pathogenic (p-VUS). PGT-M was recommended for 17/30 CNVs (56.6%), 12 (70%) of which, isolated VUS. No couple had other indications for IVF. To date, nine couples performed PGT-M for isolated VUS; LBR per-couple—55.5%. Five couples performed PGT-M for both pathogenic findings and VUS, LBR—80%. After reviewing VUS classifications, 30% remained unchanged, 20% were more severely defined, and 50% less severely defined.ConclusionThe genomic era enables detection of VUS whose definition is subject to change as additional information becomes available. The uncertainty of variants’ clinical significance and changes in VUS definition over time complicates genetic counseling. Revised guidelines for VUS interpretation and reevaluation of patient counseling before each pregnancy must be practiced when counseling them regarding the justification of PGT-M for their diagnosed VUS.

Preimplantation genetic testing for aneuploidy (PGT-A) with trophectoderm (TE) biopsy is widely applied in in vitro fertilization (IVF) to identify aneuploid embryos. However, potential safety concerns regarding biopsy and restrictions to only those embryos suitable for biopsy pose limitations. In addition, embryo mosaicism gives rise to false positives and false negatives in PGT-A because the inner cell mass (ICM) cells, which give rise to the fetus, are not tested. Here, we report a critical examination of the efficacy of noninvasive preimplantation genetic testing for aneuploidy (niPGT-A) in the spent culture media of human blastocysts by analyzing the cell-free DNA, which reflects ploidy of both the TE and ICM. Fifty-two frozen donated blastocysts with TE biopsy results were thawed; each of their spent culture medium was collected after 24-h culture and analyzed by next-generation sequencing (NGS). niPGT-A and TE-biopsy PGT-A results were compared with the sequencing results of the corresponding embryos, which were taken as true results for aneuploidy reporting. With removal of all corona-cumulus cells, the false-negative rate (FNR) for niPGT-A was found to be zero. By applying an appropriate threshold for mosaicism, both the positive predictive value (PPV) and specificity for niPGT-A were much higher than TE-biopsy PGT-A. Furthermore, the concordance rates for both embryo ploidy and chromosome copy numbers were higher for niPGT-A than TE-biopsy PGT-A. These results suggest that niPGT-A is less prone to errors associated with embryo mosaicism and is more reliable than TE-biopsy PGT-A.

Background Preimplantation genetic testing for aneuploidy and for chromosomal structural rearrangement (PGT-A/-SR) can improve clinical pregnancy rates and live birth rates, and shorten the time to pregnancy. The large-scale statistics on their efficacy and accuracy across different centres, as well as the frequency of abnormalities for each chromosome, will provide a valuable supplement to previous research. Methods Patients who had PGT-A or -SR procedures at five reproductive centres from 2018 to 2022 were recruited based on PGT-A/-SR indications. ChromInst and next-generation sequencing (NGS)-based PGT technology were utilised to detect copy number variations in embryos. Sequencing data metrics such as median absolute pairwise difference (MAPD) and detection success rate were analysed to evaluate the robustness of ChromInst. To assess ChromInst’s accuracy, the chromosomal results from amniocentesis, abortions, and neonatal blood was as the gold standard for negative PGT results; the fluorescence in situ hybridisation (FISH), which was performed on embryos that identified as aneuploid through PGT was as the gold standard for positive PGT results. The frequency of abnormalities in each chromosome was also explored in aneuploid embryos. Results A total of 5,730 embryos were tested from 1,015 patients in the study, 391 of whom had PGT-A and 624 of whom had PGT-SR. 99.5% (5,699/5,730) of the embryos had an NGS sequencing MAPD value < 0.25, and 99.3% (5,689/5,730) of the embryos achieved successful PGT-A/-SR detection. Compared with the gold standard, the concordance of negative PGT-A/-SR results was 99.8% (506/507), and that of positive results was 99.8% (1,123/1,125). The euploidy rate in the PGT-A population was 45.9% (981/2,135). The proportion of euploid + balanced embryos was highest among couples with non-polymorphic inversions (44.6%, 152/341), followed by those with Robertsonian translocations (39.0%, 293/752), and lowest among those with reciprocal translocations (22.5%, 483/2,143). Chromosomes 16, 22, and 15 had the highest frequency of autosomal trisomies among the embryos from PGT-A patients, while chromosomes 16, 22, and 21 had the highest frequency of monosomies. High-frequency chromosomes with de novo chromosomal abnormalities for trisomies and monosomies were similar in the PGT-SR patients to those in the PGT-A patients. Conclusions ChromInst-based PGT-A/-SR could accommodate operational variations among different clinical centres, ensuring accurate results through robust and stable detection performance. Prior to PGT-A/-SR, more trustworthy data could be provided to support the genetic counselling.

The field of preimplantation genetic testing (PGT) is evolving fast, and best practice advice is essential for regulation and standardisation of diagnostic testing. The previous ESHRE guidelines on best practice for preimplantation genetic diagnosis, published in 2005 and 2011, are considered outdated and the development of new papers outlining recommendations for good practice in PGT was necessary.The current updated version of the recommendations for good practice is, similar to the 2011 version, split into four documents, one of which covers the organisation of a PGT centre. The other documents focus on the different technical aspects of embryo biopsy, PGT for monogenic/single-gene defects (PGT-M) and PGT for chromosomal structural rearrangements/aneuploidies (PGT-SR/PGT-A).The current document outlines the steps prior to starting a PGT cycle, with details on patient inclusion and exclusion, and counselling and information provision. Also, recommendations are provided on the follow-up of PGT pregnancies and babies. Finally, some further recommendations are made on the practical organisation of an IVF/PGT centre, including basic requirements, transport PGT and quality management.This document, together with the documents on embryo biopsy, PGT-M and PGT-SR/PGT-A, should assist everyone interested in PGT in developing the best laboratory and clinical practice possible.