Preimplantation genetic testing: A remarkable history of pioneering, technical challenges, innovations, and ethical considerations.

Preimplantation genetic testing (PGT) has emerged as a powerful companion to assisted reproduction technologies. The origins and history of PGT are reviewed here, along with descriptions of advances in molecular assays and sampling methods, their capabilities, and their applications in preventing genetic diseases and enhancing pregnancy outcomes. Additionally, the potential for increasing accuracy and genome coverage is considered, as well as some of the emerging ethical and legislative considerations related to the expanding capabilities of PGT.

Preimplantation genetic testing in the current era, a review.

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.

Acceptance of genetic editing and of whole genome sequencing of human embryos by patients with infertility before and after the onset of the COVID-19 pandemic.

RESEARCH QUESTION: Has acceptance of heritable genome editing (HGE) and whole genome sequencing for preimplantation genetic testing (PGT-WGS) of human embryos changed after the onset of COVID-19 among infertility patients? DESIGN: A written survey conducted between April and June 2018 and July and December 2021 among patients at a university-affiliated infertility practice. The questionnaire ascertained the acceptance of HGE for specific therapeutic or genetic 'enhancement' indications and of PGT-WGS to prevent adult disease. RESULTS: In 2021 and 2018, 172 patients and 469 patients (response rates: 90% and 91%, respectively) completed the questionnaire. In 2021, significantly more participants reported a positive attitude towards HGE, for therapeutic and enhancement indications. In 2021 compared with 2018, respondents were more likely to use HGE to have healthy children with their own gametes (85% versus 77%), to reduce disease risk for adult-onset polygenic disorders (78% versus 67%), to increase life expectancy (55% versus 40%), intelligence (34% versus 26%) and creativity (33% versus 24%). Fifteen per cent of the 2021 group reported a more positive attitude towards HGE because of COVID-19 and less than 1% a more negative attitude. In contrast, support for PGT-WGS was similar in 2021 and 2018. CONCLUSIONS: A significantly increased acceptance of HGE was observed, but not of PGT-WGS, after the onset of COVID-19. Although the pandemic may have contributed to this change, the exact reasons remain unknown and warrant further investigation. Whether increased acceptability of HGE may indicate an increase in acceptability of emerging biomedical technologies in general needs further investigation.

Comparison of euploid blastocyst expansion with subgroups of single chromosome, multiple chromosome, and segmental aneuploids using an AI platform from donor egg embryos.

PURPOSE: This retrospective observational study compares how different classes of blastocyst genotypes from egg donor cycles differentially blastulate and expand using a standard assay. METHODS: Quantitative measurements of expansion utilized a customized neural network that segments all sequential time-lapse images during the first 10 h of expansion. RESULTS: Analyses were performed using two developmental time perspectives using time-lapse imaging. The first was the time to blastocyst formation (tB), which broadly reflects variations in developmental rate. Euploidy peaked at 100-115 h from fertilization. In contrast, aneuploidy peaks flanked this interval bi-modally. These distributions limit ploidy discrimination based upon traditional standard grading features when assessed in real time. In contrast, from the second perspective of progressive blastocyst expansion that is normalized to each individual blastocyst's tB time, euploidy was significantly increased at expansion values > 20,000µ2 across all tB intervals studied. A Cartesian coordinate plot graphically summarizes information useful to rank order blastocysts within cohorts for transfer. Defined aneuploidy subgroups, distinguished by the number and complexity of chromosomes involved, also showed distributive differences from both euploids and from each other. A small subset of clinically significant trisomies did not show discriminating features separating them from other euploids. CONCLUSION: A standard assay of blastocyst expansion normalized to each individual blastocyst's time of blastocyst formation more usefully discriminates euploidy from aneuploidy than real-time expansion comparisons using absolute developmental time from fertilization.

Polygenic risk score for embryo selection-not ready for prime time.

Numerous chronic diseases have a substantial hereditary component. Recent advances in human genetics have allowed the extent of this to be quantified via genome-wide association studies, producing polygenic risk scores (PRS), which can then be applied to individuals to estimate their risk of developing a disease in question. This technology has recently been applied to embryo selection in the setting of IVF and preimplantation genetic testing, with limited data to support its utility. Furthermore, there are concerns that the inherent limitations of PRS makes it ill-suited for use as a screening test in this setting. There are also serious ethical and moral questions associated with this technology that are yet to be addressed. We conclude that further research and ethical reflection are required before embryo selection based on PRS is offered to patients outside of the research setting.

IVF outcomes of embryos with abnormal PGT-A biopsy previously refused transfer: a prospective cohort study.

STUDY QUESTION: What are the outcomes for patients who choose to move embryos diagnosed as abnormal by preimplantation genetic testing for aneuploidy (PGT-A) to a new institution for transfer after the diagnosing institution refused to transfer them? SUMMARY ANSWER: Many patients seek to have selected embryos with PGT-A abnormal trophectoderm biopsies transferred recognizing that these embryos can still offer a chance of pregnancy and live birth. WHAT IS KNOWN ALREADY: : PGT-A is a widely practiced method of selecting embryos for transfer based on biopsy of a few cells. Many clinical practices refuse to transfer PGT-A abnormal embryos even when there are no other 'normal' embryos available. STUDY DESIGN, SIZE, DURATION: This is a prospective cohort of 69 couples who, since 2014, moved a total of 444 PGT-A abnormal embryos previously refused transfer at their parent institutions to our practice. Among these, 50 patients have, thus far, undergone 57 transfer cycles of 141 embryos. PARTICIPANTS/MATERIALS, SETTING, METHODS: Embryos diagnosed at other institutions by PGT-A as abnormal (mostly using next generation sequencing) were moved to our academically affiliated private fertility and research center in New York City. Female age at retrieval was 41.35 ± 3.98 years, 74% were Caucasian, 12% Asian and 10% were of African descent. All embryos identified as PGT-A abnormal among prospectively identified couples were recorded in our center's registry. MAIN RESULTS AND THE ROLE OF CHANCE: Among the 144 embryos transferred 102 (72.3%) had only 1 or 2 chromosomal abnormalities, 30 (21.3%) had 3 or more and 9 (6.4%) were 'undiagnosed' because of degraded DNA, yet still had been refused transfer. Transfer of PGT-A abnormal embryos resulted in 8 live births, 11 miscarriages and no voluntary terminations. One child was born with a segmental duplication and required repair of coarctation of the aorta as a newborn. Many couples with only PGT-A abnormal embryos are willing to have their PGT-A abnormal embryos transferred and such transfers can result in the establishment of ongoing euploid pregnancies and live births. LIMITATIONS, REASONS FOR CAUTION: Findings in this case series represent couples who chose to have their embryos transferred after having been refused transfer elsewhere and may not be representative of the wider population of couples undergoing IVF with PGT-A in general. Not all abnormal phenotypes present in the immediate postnatal period so it will be important to continue to follow the development of these children. WIDER IMPLICATIONS OF THE FINDINGS: PGT-A can result in a clinics refusal to transfer embryos with abnormal PGT-A biopsies, even those with mosaic findings, consequently large numbers of infertile women are prematurely advised that their only chance of motherhood is through third-party egg-donation. STUDY FUNDING/COMPETING INTEREST(S): This work was supported by intramural funds from the Center for Human Reproduction and the not-for-profit research Foundation for Reproductive Medicine, both in New York, NY, USA. N.G. and D.H.B. are listed as co-inventors on several U.S. patents. One of these patents (US Patent# 7,615,544) relates to pre-supplementation of hypo-androgenic infertile women with androgens, such as DHEA and testosterone and, therefore, at least peripherally related to the subject of this manuscript. N.G. and D.F.A. also received travel funds and speaker honoraria from several pharmaceutical and medical device companies, though none related to the here presented subject and manuscript. N.G. is a shareholder in Fertility Nutraceuticals and he and D.H.B. receive royalty payments from Fertility Nutraceuticals LLC. TRIAL REGISTRATION NUMBER: N/A.

Which assisted reproductive technology (ART) treatment strategy is the most clinically and cost-effective for women of advanced maternal age: a Markov model.

OBJECTIVE: To evaluate the clinical and cost-effectiveness of preimplantation genetic testing for aneuploidy, social freezing, donor and autologous assisted reproductive technology (ART) treatment strategies for women aged 35-45 following 6-12 months of infertility. METHODS: Four Markov decision-analytic models comprising: (i) Preimplantation genetic testing for aneuploidy (PGT-A); (ii) autologous ART from age 40 using oocytes cryopreserved at age 32 (social freezing); (iii) ART using donated oocytes (donor ART); (iv) standard autologous ART treatment (standard care) were developed for a hypothetical cohort of 35 to 45 years old ART naïve women with 6-12 months of infertility. Input probabilities for key parameters including live birth rates were obtained from the available literature. Deterministic and probabilistic sensitivity analyses were conducted to address uncertainty in estimating the parameters and around the model's assumptions. Cost effectiveness was assessed from both societal and patient perspectives . RESULT(S): For infertile women at age 40 and above, social freezing is the most cost-saving strategy with the highest chance of a cumulative live birth at a lowest cost from a societal perspective. PGT-A and donor ART were associated with higher treatment costs and cumulative live-birth rates compared with the autologous ART. Among the four ART strategies, standard autologous ART has the lowest cumulative live birth rate of 45% at age 35 and decreasing to 1.6% by age 45 years. At a willingness-to-pay threshold of Australian dollars (A$)50,000, our model shows all alternative treatment strategies -PGT-A, social freezing and donor ART have a higher probability of being cost-effective compared to the standard autologous ART treatment. However, higher out-of-pocket expenditure may impede their access to these alternate strategies. CONCLUSION: Given current evidence, all alternate strategies have a higher probability of being cost-effective compared to the standard autologous ART treatment. Whether this represents value for money depends on societal and individual's willingness-to-pay for children conceived with ART treatment.

Chromosome aneuploidy analysis in embryos derived from in vivo and in vitro matured human oocytes.

BACKGROUND: In vitro oocyte maturation (IVM) is being increasingly approached in assisted reproductive technology (ART). This study aimed to evaluate the quality of embryos generated by in-vitro matured immature follicles, as a guideline for further clinical decision-making. METHODS: A total of 52 couples with normal karyotypes underwent in vitro fertilization, and 162 embryos were donated for genetic screening. Embryos in IVF group were generated by mature follicles retrieved during gonadotrophin-stimulated in vitro fertilization (IVF) cycles. And embryos in IVM group were fertilized from IVM immature oocytes. RESULTS: The average age of the women was 30.50 ± 4.55 years (range 21-42 years) with 87 embryos from IVF group and 75 embryos from IVM group. The rate of aneuploid with 28 of the 87 (32.2%) embryos from IVF group and 21 of the 75 (28%) embryos from IVM group, with no significant difference. The frequency of aneuploid embryos was lowest in the youngest age and increased gradually with women's age, whether in IVF group or IVM group and risen significantly over 35 years old. The embryos with morphological grade 1 have the lowest aneuploidy frequency (16.6%), and increase by the grade, especially in IVF group. In grade 3, embryos in IVM group were more likely to be euploid than IVF group (60% vs 40%, respectively). CONCLUSIONS: IVM does not affect the quality of embryos and does not increase the aneuploidy rate of embryos. It is clinically recommended that women more than 35 years have a high aneuploidy rate and recommended to test by PGS (strongly recommended to screened by PGS for women more than 40 years). Women aged less than 35 years old for PGS according to their physical and economic conditions. Embryo with poor quality is also recommended to test by PGS, especially for grade III embryos.

Reproductive outcomes after preimplantation genetic testing in mosaic Turner syndrome: a retrospective cohort study of 100 cycles.

PURPOSE: The purpose of this study is to explore the reproductive outcomes of women with Turner syndrome (TS) in preimplantation genetic testing (PGT) cycles. METHODS: A retrospective study of 100 controlled ovarian stimulating cycles, 68 TS (sixty-four mosaic Turner syndrome (MTS) and four pure Turner syndrome (PTS)) women underwent PGT was conducted from 2013 to 2018. RESULTS: Embryo X chromosome abnormal rates of TS women were significantly higher than women with normal karyotype (7.04 vs 1.61%, P<0.01). Cumulative live birth rates (CLBR) after PGT-NGS treatment were lower in TS than control (31.15 vs 45.59%, P<0.05). Clinical pregnancy rates per transfer (CPR), miscarriage rates (MR) and live birth rates per transfer (LBR) remained comparable between TS and control group. Reproductive outcomes (X chromosome abnormal rates, CPR, MR, LBR and CLBR) among low (<10%), medium (10-50%) and high (>50%) level 45,X mosaicism groups were not statistically different. CONCLUSIONS: To avoid high risk of embryo X chromosome abnormalities, prenatal or preimplantation genetic testing should be recommended to mosaic or pure TS patients.

Successful fertility outcome in a couple with recurrent implantation failure and testicular cancer survivor: A case report.

A couple of Indo-American descent, presented to our clinic with a history of primary infertility and repeated IVF implantation failure. Male was a testicular cancer survivor who had erectile dysfunction and azoospermia. Female partner had polycystic ovarian syndrome (PCOD). She had three unsuccessful attempts of embryo transfer at another fertility clinic. At our clinic, she underwent controlled ovarian stimulation, COH started from day two period with rFSH (follicle stimulating hormone) followed by HMG (human menopausal gondadotropin) with antagonist protocol followed by preimplantation genetic screening of embryos. Subsequently, she began HRT (hormone replacement Therapy) protocol for ERA cycle from day 2, where she also underwent hysteroscopy on day 7. After five days of progesterone supplementation, she underwent endometrial biopsy for ERA (endometrial receptivity assay). Frozen embryo transfer cycle was started with the same HRT protocol used in her previous ERA cycle. Post embryo transfer, immunotherapy with steroids and fortnightly intralipids was given. Pregnancy test was positive with a BHCG value of 290 mIU/mL. and she delivered naturally after 39 completed weeks of gestation. A stepwise personalized treatment approach maximizes the chances of a successful outcome in presence of both male and female factors. Frozen or fresh sperms for ICSI with PGS along with hysteroscopy, ERA and under cover of immune modulation yielded positive results.

Mosaicism in Preimplantation Human Embryos: When Chromosomal Abnormalities Are the Norm.

Along with errors in meiosis, mitotic errors during post-zygotic cell division contribute to pervasive aneuploidy in human embryos. Relatively little is known, however, about the genesis of these errors or their fitness consequences. Rapid technological advances are helping to close this gap, revealing diverse molecular mechanisms contributing to mitotic error. These include altered cell cycle checkpoints, aberrations of the centrosome, and failed chromatid cohesion, mirroring findings from cancer biology. Recent studies are challenging the idea that mitotic error is abnormal, emphasizing that the fitness impacts of mosaicism depend on its scope and severity. In light of these findings, technical and philosophical limitations of various screening approaches are discussed, along with avenues for future research.

The 2019 PGDIS position statement on transfer of mosaic embryos within a context of new information on PGT-A.

BACKGROUND: A recently published Position Statement (PS) by the Preimplantation Genetics Diagnosis International Society (PGDIS) regarding utilization of preimplantation genetic testing for aneuploidy (PGT-A) in association with in vitro fertilization (IVF) contained inaccuracies and misrepresentations. Because opinions issued by the PGDIS have since 2016 determined worldwide IVF practice, corrections appear of importance. METHODS: The International Do No Harm Group in IVF (IDNHG-IVF) is a spontaneously coalesced body of international investigators, concerned with increasing utilization of add-ons to IVF. It is responsible for the presented consensus statement, which as a final document was reached after review of the pertinent literature and again revised after the recent publication of the STAR trial and related commentaries. RESULTS: In contrast to the PGDIA-PS, we recommend restrictions to the increasing, and by IVF centers now often even mandated, utilization of PGT-A in IVF cycles. While PGT-A has been proposed as a tool for achieving enhanced singleton livebirth outcomes through embryo selection, continued false-positive rates and increasing evidence for embryonic self-correction downstream from the testing stage, has led IDNHG-IVF to conclude that currently available data are insufficient to impose overreaching recommendations for PGT-A utilization. DISCUSSION: Here presented consensus offers an alternative to the 2019 PGDIS position statement regarding utilization of preimplantation genetic testing for aneuploidy (PGT-A) in association with in vitro fertilization (IVF). Mindful of what appears to offer best outcomes for patients, and in full consideration of patient autonomy, here presented opinion is based on best available evidence, with the goal of improving safety and efficacy of IVF and minimizing wastage of embryos with potential for healthy births. CONCLUSIONS: As the PGDIS never suggested restrictions on clinical utilization of PGT-A in IVF, here presented rebuttal represents an act of self-regulation by parts of the IVF community in attempts to control increasing utilization of different unproven recent add-ons to IVF.

Preliminary assessment of aneuploidy rates between the polar, mid and mural trophectoderm.

The objective of this study is to compare aneuploidy rates between three distinct areas of the human trophectoderm: mural, polar and a region in between these two locations termed the 'mid' trophectoderm. This is a cohort study on in vitro fertilization (IVF) patients undergoing comprehensive chromosome screening at the blastocyst stage at a private IVF clinic. All embryos underwent assisted hatching on day 3 with blastocyst biopsy and comprehensive chromosome screening. Biopsied blastocysts were divided into three groups depending on which area (polar, mid, or mural) of the trophectoderm was protruding from the zona pellucida and biopsied. Aneuploidy rates were significantly higher with cells from the polar region of the trophectoderm (56.2%) compared with cells removed from the mural region of the trophectoderm (30.0%; P = 0.0243). A comparison of all three areas combined also showed a decreasing trend, but this did not reach clinical significance, polar (56.2%), mid (47.4%) and mural trophectoderm (30.0%; P = 0.1859). The non-concordance demonstrated between polar and mural trophectoderm can be attributed to biological occurrences including chromosomal mosaicism or procedural differences between embryologists.

Cryopreservation of euploid blastocysts obtained after fertilization of in vitro matured ovarian tissue oocytes: a case report.

With the increased rate of stable remission after gonadotoxic cancer treatment, new methods of fertility preservation are required in order to provide the best possible care for oncological patients. Here, we report an original case of euploid blastocyst cryopreservation after in vitro maturation of ovarian tissue oocytes (OTO IVM). Thirty-three oocytes were obtained from the ovarian tissue after ovariectomy in the breast cancer patient. Six out of 12 matured oocytes fertilized successfully and 3 blastocysts were formed. Genetic investigation for mutations associated with this type of malignancy found that the patient is not a carrier. Preimplantation genetic testing was performed only for aneuploidies and found all 3 blastocysts to be euploid and suitable for embryo transfer. Our study showed that the ovarian tissue oocytes matured in vitro have the potential for euploid blastocyst formation after ICSI which could be screened for aneuploidies and inherited mutations and then be vitrified in order to provide the best fertility preservation strategy for women with cancer.

The PGS/PGT-A controversy in IVF addressed as a formal conflict resolution analysis.

PURPOSE: To use conflict resolution analysis on the conflict between proponents and opponents of preimplantation genetic testing for aneuploidy (PGT-A), previously called preimplantation genetic screening (PGS). METHODS: Considered in conflict analysis a case study, we reviewed the English literature based on key-word searches at www.pubmed.com and www.google.com, and interviewed professional opinion leaders and other actor-representatives. This analysis was the product of a mandated externship by L.M. at the Foundation for Reproductive Medicine (FRM), as part of the Master of Science Program in Negotiations and Conflict Resolution at Columbia University, New York, NY. RESULTS: Initially a typical difference of opinion, conflict evolved after proponents rejected studies that failed to confirm expected benefits, and authors felt demeaned by their criticism. Becoming "destructive," the conflict evolved according to Glasl's escalation model stages. Proponents became continuous attractors. Unable to produce validations for PGT-A, proponents moved goal posts through 3 stages (PGS 1.0-PGS 3.0). Ultimately concurring that pregnancy and live birth rates are unaffected, they started claiming new benefits. CONCLUSIONS: The FRM underwrote this study as a starting tool for a conflict resolution process. A consensus building conference of stakeholders appears as of this point to represent the most promising potential intervention. The goal of such a conference should be sustainable consensus about clinical utilization of PGS/PGT-A in IVF, based on transparent and validated criteria. A potential date for such a conference is set for 2020.

Variations in chromosomal aneuploidy rates in IVF blastocysts and early spontaneous abortion chorionic villi.

PURPOSE: To compare chromosomal aberrations and aneuploidy features in (i) blastocysts following intracytoplasmic sperm injection (ICSI) and trophectoderm (TE) biopsy using preimplantation genetic screening (PGS) and (ii) early spontaneous abortion chorionic villus biopsies (SA-CVB) using single-nucleotide polymorphism (SNP) array detection. METHODS: We retrospectively reviewed the data for 1014 TEs from 220 PGS cycles and 1724 SA-CVBs originating from naturally pregnant couples and patients undergoing assisted reproductive technology (ART) during 2017 to 2018. SNP array was applied in both PGS and SA-CVBs detection. Aberrations were defined, and the frequency and ratio of each chromosome aberration were compared between the two groups. RESULTS: There were more abnormalities in TEs in the form of complex chromosome aneuploidies and monosomies, while SA-CVBs had more trisomies, sex chromosome abnormalities, and polyploidies. In both groups, chromosomal aneuploidies (including monosomies and trisomies) were confined to chromosomes 14, 15, 16, 18, 21, and 22, but showed varying distributions across the groups. Aneuploidy of chromosome 22 was most frequent in TEs, whereas that of chromosome 16 predominated in SA-CVBs. Among the sex chromosome abnormalities, X monosomies were significantly more prevalent in SA-CVBs. CONCLUSIONS: Chromosomal aberrations and aneuploidy manifested specific characteristics that differed between TEs and SA-CVBs, which indicates that distinct chromosomal abnormalities can affect certain developmental stages of embryos. Further analysis is needed to explore the chromosomal mechanisms affecting embryo development and implantation. Such information will help clinical assessments in prenatal diagnosis and reduce the incidence of genetically abnormal fetuses.

Next-generation sequencing analysis of each blastomere in good-quality embryos: insights into the origins and mechanisms of embryonic aneuploidy in cleavage-stage embryos.

PURPOSE: To explore the whole-chromosome status, origins, and mechanisms of chromosomal abnormalities in good-quality cleavage embryos using multiple annealing and looping-based amplification cycle (MALBAC) sequencing. METHODS: The embryos studied came from7 patients (maternal aged 26-35) who had healthy birth from the same IVF cycles. These 21 frozen day 3 good-quality embryos were thawed and disaggregated into individual blastomere. Each blastomere was collected and analyzed by MALBAC sequencing. RESULTS: Conclusive results were obtained from a high percentage of blastomeres (95.3%). A total of 46.6% of blastomeres were diploid, 53.4% were abnormal, and 28.0% had complex aneuploidy. Out of 21 embryos, 3 (14.3%) were normal and 18 (85.7%) were mosaics, showing the occurrence of mitotic errors; aneuploidy was confirmed in all cells of 4 of the 18 embryos, which showed the coexistence of meiotic errors. Conclusive results were obtained from all blastomeres of 15 embryos (71.4%, 15/21), which enabled us to reconstruct the cell lineage on the basis of the chromosomal content of the blastomeres in each division. There were 9 mitotic errors (8.7%, 9/103): nondisjunction accounted for 88.9% (8/9), and endoreplication accounted for 11.1% (1/9). CONCLUSIONS: In good-quality embryos, there was a high rate and diverse array of chromosomal abnormalities. Morphological evaluation does not appear to assist in the reduction in meiotic errors from parental origins. Mitotic errors were common, and nondisjunction was found to be the main mechanism causing malsegregation during the cleavage divisions.

Preimplantation Genetic Testing: Where We Are Today.

BACKGROUND: Preimplantation genetic testing (PGT) is widely used today in in-vitro fertilization (IVF) centers over the world for selecting euploid embryos for transfer and to improve clinical outcomes in terms of embryo implantation, clinical pregnancy, and live birth rates. METHODS: We report the current knowledge concerning these procedures and the results from different clinical indications in which PGT is commonly applied. RESULTS: This paper illustrates different molecular techniques used for this purpose and the clinical significance of the different oocyte and embryo stage (polar bodies, cleavage embryo, and blastocyst) at which it is possible to perform sampling biopsies for PGT. Finally, genetic origin and clinical significance of embryo mosaicism are illustrated. CONCLUSIONS: The preimplantation genetic testing is a valid technique to evaluated embryo euploidy and mosaicism before transfer.

Current status of spent embryo media research for preimplantation genetic testing.

In recent years, a growing body of literature has emerged investigating the clinical utility of spent embryo media (SEM) for preimplantation genetic testing for aneuploidy (PGT-A) (Hammond et al. in Fertil Steril. 107(1):220-8, 2017; Xu et al. in Proc Natl Acad Sci USA. 113(42):11907-12, 2016; Shamonki et al. in Fertil Steril. 106(6):1312-8, 2016; Feichtinger et al. in Reprod BioMed Online. 34(6):583-9, 2017; Vera-Rodriguez et al. in Hum Reprod. 33(4):745-56, 2018; Kuznyetsov et al. in PLoS One. 13(5):e0197262, 2018; Ho et al. in Fertil Steril. 110(3):467-75, 2018; Capalbo et al. in Fertil Steril. 110(5):870-9, 2018). Most of these studies have reported moderate success rates, suggesting the need for improvements in sensitivity and specificity. The concordance between spent media and embryo biopsy or whole embryo was reported to be between 30.4 and 90%, with 50-70% correlation being the most representative (Xu et al. in Proc Natl Acad Sci USA. 113(42):11907-12, 2016; Shamonki et al. in Fertil Steril. 106(6):1312-8, 2016; Feichtinger et al. in Reprod BioMed Online. 34(6):583-9, 2017; Vera-Rodriguez et al. in Hum Reprod. 33(4):745-56, 2018; Kuznyetsov et al. in PLoS One. 13(5):e0197262, 2018; Ho et al. in Fertil Steril. 110(3):467-75, 2018). Here, we will analyze all spent media testing strategies including SEM collection methods, whole genome amplification (WGA) strategies, chromosome copy number detection, and bioinformatics analysis tools. We will propose improvements to further increase the accuracy and sensitivity of the assay before bringing PGT-A with SEM into the clinical sphere.

Hormone replacement versus natural frozen embryo transfer for euploid embryos.

PURPOSE: The goal of this study is to investigate hormone replacement (HR) versus natural frozen embryo transfer outcomes for euploid embryos. METHODS: This is a retrospective cohort study at an academic medical center of patients undergoing in vitro fertilization with 24-chromosome day 5/6 preimplantation genetic testing for aneuploidies (PGT-A), from 2014 to 2018 using euploid single embryo frozen transfer. Multivariable logistic regression was used to study the association between transfer outcomes (ongoing pregnancy and miscarriage) with type of frozen euploid embryo transfer (HR versus natural) while controlling for multiple patient and cycle confounders. RESULTS: From a total of 389 cycles, 45.0% utilized HR frozen embryo transfer and 55.0% were natural cycles. We found that when compared to HR frozen embryo transfer, natural cycle frozen embryo transfer had significantly higher ongoing pregnancy rates (aOR 2.05, 1.27-3.31, p = 0.003). There was no significant difference in miscarriage rates between the two groups (aOR for natural 0.69, 95% CI 0.37-1.32, p = 0.27). When limiting the analysis to only the first transfer at our institution, findings were similar of higher ongoing pregnancy rates and no difference in miscarriage rates. CONCLUSIONS: In our multivariate analysis, we found that natural cycle single euploid frozen embryo transfer was associated with significantly higher ongoing pregnancy rates than HR transfer, with no difference in miscarriage rates.