Embryology with precision: effective quality control in the in vitro fertilization laboratory.

The purpose of this review is to address the critical need for standardization and clarity in the use of key performance indicators (KPIs) within the realm of in vitro fertilization (IVF), particularly emphasizing the integration of preimplantation genetic testing (PGT) processes. This review is timely and relevant given the persistently modest success rates of IVF treatments, which stand at approximately 30%, and the growing complexity of IVF procedures, including PGT practices. The review synthesizes recent findings across studies focusing on technical and clinical KPIs in embryology and genetic laboratories, identifying gaps in current research and practice, particularly the lack of standardized KPIs and terminology. Recent findings highlighted include the critical evaluation of technical KPIs such as Intracytoplasmic Sperm Injection (ICSI) fertilization rates, embryo development rates, and laboratory performance metrics, alongside clinical KPIs like the proportion of mature oocytes and clinical pregnancy rates. Notably, the review uncovers a significant gap in integrating and standardizing KPIs for PGT applications, which is essential for improving IVF outcomes and genetic diagnostic accuracy. The implications of these findings are profound for both clinical practice and research. For clinical practice, establishing a standardized set of KPIs, especially for PGT, could significantly enhance the success rates of IVF treatments by providing clearer benchmarks for quality and performance. For research, this review underscores the necessity for further studies to close the identified gaps, promoting a more integrated and standardized approach to KPIs in IVF and PGT processes. This comprehensive approach will not only aid in improving clinical outcomes but also in advancing the field of reproductive medicine.

Maternal and neonatal outcomes in pregnancies conceived after preimplantation genetic testing.

OBJECTIVE: To determine whether preimplantation genetic testing (PGT) is associated with an increase in adverse maternal or neonatal outcomes in singleton and twin live births conceived via in vitro fertilization (IVF). METHOD: Retrospective cohort of live births resulting from IVF within a university health system between January 2014 and August 2019. Adverse maternal outcomes (e.g., hypertensive disorders of pregnancy, abnormal placentation, and preterm birth), and adverse neonatal outcomes were compared in singleton and twin pregnancies conceived after transfer of one or two PGT-screened euploid embryos versus untested embryos in separate analyses. Multivariate backwards-stepwise logistic regression was used to adjust for potential confounders. RESULTS: Of 1160 live births, 539 (46.5%) resulted from PGT-screened embryos, 1015 (87.5%) were singletons, and 145 (12.5%) were twins. After adjusting for potential confounders, there were no significant differences between the two groups with respect to hypertensive disorders of pregnancy, fetal growth restriction, preterm birth, and adverse neonatal outcomes in both analyses, as well as abnormal placentation for singletons. CONCLUSION: Our data suggest that IVF with PGT is not associated with an increased risk of adverse maternal or neonatal outcomes compared to IVF without PGT. Further research utilizing larger cohorts are needed before drawing definitive conclusions.

Using outcome data from one thousand mosaic embryo transfers to formulate an embryo ranking system for clinical use.

OBJECTIVE: To study how the attributes of mosaicism identified during preimplantation genetic testing for aneuploidy relate to clinical outcomes, in order to formulate a ranking system of mosaic embryos for intrauterine transfer. DESIGN: Compiled analysis. SETTING: Multi-center. PATIENT(S): A total of 5,561 euploid blastocysts and 1,000 mosaic blastocysts used in clinical transfers in patients undergoing fertility treatment. INTERVENTION(S): None. MAIN OUTCOME MEASURE(S): Implantation (gestational sac), ongoing pregnancy, birth, and spontaneous abortion (miscarriage before 20 weeks of gestation). RESULT(S): The euploid group had significantly more favorable rates of implantation and ongoing pregnancy/birth (OP/B) compared with the combined mosaic group or the mosaic group affecting only whole chromosomes (implantation: 57.2% vs. 46.5% vs. 41.8%; OP/B: 52.3% vs. 37.0% vs. 31.3%), as well as lower likelihood of spontaneous abortion (8.6% vs. 20.4% vs. 25%). Whole-chromosome mosaic embryos with level (percent aneuploid cells) <50% had significantly more favorable outcomes than the ≥50% group (implantation: 44.5% vs. 30.4%; OP/B: 36.1% vs. 19.3%). Mosaic type (nature of the aneuploidy implicated in mosaicism) affected outcomes, with a significant correlation between number of affected chromosomes and unfavorable outcomes. This ranged from mosaicism involving segmental abnormalities to complex aneuploidies affecting three or more chromosomes (implantation: 51.6% vs. 30.4%; OP/B: 43.1% vs. 20.8%). Combining mosaic level, type, and embryo morphology revealed the order of subcategories regarding likelihood of positive outcome. CONCLUSION(S): This compiled analysis revealed traits of mosaicism identified with preimplantation genetic testing for aneuploidy that affected outcomes in a statistically significant manner, enabling the formulation of an evidence-based prioritization scheme for mosaic embryos in the clinic.

Preimplantation Genetic Testing for Aneuploidy - a Castle Built on Sand.

Preimplantation genetic testing for aneuploidy (PGT-A) has become a routine add-on for in vitro fertilization (IVF) to determine whether human embryos are to be clinically utilized or disposed of. Studies claiming IVF outcome improvements following PGT-A, however, used highly selected patient populations or inappropriate statistical methodologies. PGT-A was never clinically validated in its ability to define a human embryo as chromosomal normal, mosaic, or aneuploid, nor certified by a regulatory body, or an authoritative professional organization. Because of a high false-positive rate, PGT-A, actually reduces live IVF birth chances for many patients. Furthermore, in recent studies the PGT-A hypothesis was demonstrated to be mistaken for biological, mathematical and technical reasons. PGT-A, therefore, should clinically only be offered within experimental study frameworks.

A multicenter, prospective, blinded, nonselection study evaluating the predictive value of an aneuploid diagnosis using a targeted next-generation sequencing-based preimplantation genetic testing for aneuploidy assay and impact of biopsy.

OBJECTIVE: To determine the predictive value of an aneuploid diagnosis with a targeted next-generation sequencing-based preimplantation genetic testing for aneuploidy (PGT-A) assay in prognosticating the failure of a successful delivery. DESIGN: Prospective, blinded, multicenter, nonselection study. All usable blastocysts were biopsied, and the single best morphologic blastocyst was transferred before genetic analysis. Preimplantation genetic testing for aneuploidy was performed after clinical outcome was determined. Clinical outcomes were compared to PGT-A results to calculate the predictive value of a PGT-A aneuploid diagnosis. SETTING: Fertility centers. PATIENT(S): Couples undergoing their first in vitro fertilization cycle without recurrent pregnancy loss, antral follicle count < 8, or body mass index ≥ 35 kg/m2. INTERVENTION(S): None. MAIN OUTCOME MEASURE(S): The primary outcome was the ability of the analytical result of aneuploid to predict failure to deliver (clinical result). A secondary outcome was the impact of the trophectoderm biopsy on sustained implantation. RESULT(S): Four hundred two patients underwent 484 single, frozen, blastocyst transfers. The PGT-A aneuploid diagnosis clinical error rate was 0%. There was no difference in sustained implantation between the study group and an age-matched control group, where biopsy was not performed (47.9% vs. 45.8). CONCLUSION(S): The PGT-A assay evaluated was highly prognostic of failure to deliver when an aneuploid result was obtained. Additionally, the trophectoderm biopsy had no detectable adverse impact on sustained implantation. CLINICAL TRIAL REGISTRATION NUMBERS: NCT02032264 and NCT03604107.

Clinical management of mosaic results from preimplantation genetic testing for aneuploidy (PGT-A) of blastocysts: a committee opinion.

Since the advent of preimplantation genetic testing for aneuploidy (PGT-A) in the 1990s, substantial changes in test methodology and technology now allow the detection and reporting of intermediate chromosome copy number (commonly referred to as mosaicism) for aneuploidy in a trophectoderm biopsy sample. Clinicians are grappling with how to interpret such findings and how to counsel patients about embryo transfer decision-making. This document reviews the available literature and outlines the various issues surrounding the reporting of intermediate copy number and consideration of storage or transfer of blastocysts with intermediate copy number results. This document does not endorse, nor does it suggest that PGT-A is appropriate for all cases of in vitro fertilization.

Aneuploid embryo transfer: clinical policies and provider opinions at United States fertility clinics.

OBJECTIVE: To describe institutional clinical policies and individual provider opinions regarding aneuploid embryo transfer (aET). DESIGN: A survey about clinical policies was electronically sent to Society for Assisted Reproductive Technology (SART) member laboratory directors, and a separate survey about personal opinions was electronically sent to all SART members. SETTING: Not applicable. PATIENTS: Patients pursuing preimplantation genetic testing for aneuploidy (PGT-A). INTERVENTION: Not applicable. MAIN OUTCOME MEASURES: Current clinical policies about aET were described. Individual provider opinions about aET in the context of specific aneuploidies and mosaicism were also described. RESULTS: A total of 48 laboratory directors and 212 individual providers responded to their respective surveys. Twelve (25%) clinics report that they do not have a policy regarding aET, but clinics performing PGT-A in >100 cycles per year were more likely to have a policy. Half of the individual providers agree that an embryo with trisomy 21 should be available for aET, but most disagreed with aET of embryos with other aneuploidies and most were either unsure about or unwilling to transfer embryos with mosaicism. Those who worked in primarily patient-facing roles held more agreeable opinions regarding aET. CONCLUSION: There is no consensus regarding ideal clinical policies for aET. The wide range of current clinical practices and individual provider opinions regarding under what circumstances, if any, aET should be available to patients indicates that this is a divisive issue among ART providers, and there is a clear need for specific professional guidelines to address this issue.

Optimized NGS Approach for Detection of Aneuploidies and Mosaicism in PGT-A and Imbalances in PGT-SR.

The detection of chromosomal aneuploidies and mosaicism degree in preimplantation embryos may be essential for achieving pregnancy. The aim of this study was to determine the robustness of diagnosing homogenous and mosaic aneuploidies using a validated algorithm and the minimal resolution for de novo and inherited deletions and duplications (Del/Dup). Two workflows were developed and validated: (a,b) preimplantation genetic testing for uniform whole and segmental aneuploidies, plus mixtures of euploid/aneuploid genomic DNA to develop an algorithm for detecting mosaicism; and (c) preimplantation genetic testing for structural rearrangements for detecting Del/Dup ≥ 6 Mb. Next-generation sequencing (NGS) was performed with automatic library preparation and multiplexing up to 24-96 samples. Specificity and sensitivity for PGT-A were both 100% for whole chromosomes and segmentals. The thresholds stablished for mosaicism were: euploid embryos (<30% aneuploidy), low mosaic (from 30% to <50%), high mosaic (50-70%) or aneuploid (>70%). In the PGT-SR protocol, changes were made to increase the detection level to ≥6 Mb. This is the first study reporting an accurate assessment of semiautomated-NGS protocols using Reproseq on pools of cells. Both protocols allow for the analysis of homogeneous and segmental aneuploidies, different degrees of mosaicism, and small Del/Dup with high sensitivity and specificity.

Three simple metrics to define in vitro fertilization success rates.

Describing clinical outcomes from assisted reproduction technology (ART) treatment cycles has been an evolving challenge throughout the world. Three simple metrics provide a transparent and highly accurate summary of ART outcomes. The first metric is the probability of having no embryos available to transfer. This metric incorporates all causes of failure from initiation of the treatment cycle up to the point immediately before actual embryo transfer. Patients will know what the risk is of failing, whether it is due to poor follicular stimulation, failed fertilization, poor embryo development, or abnormal preimplantation genetic testing for aneuploidy (PGT-A) results. The second and most important metric is sustained implantation rate: the probability that any transferred embryo will implant and progress to delivery. In the event of a single-embryo transfer, the metric is identical to delivery rate per transfer. By calculating per embryo, it provides a summary of the quality of outcomes within the program without the obscuring effect of multiple-embryo transfer. The final metric is the number of supernumerary embryos cryopreserved during the cycle. This speaks to the efficiency of the process by providing an estimate of potential benefits which may come from an additional transfer should the first one be unsuccessful or even to allow the couple to pursue an additional child without another full ART cycle. These metrics are easy to calculate and provide a detailed picture of the outcomes attained by the program.

Introduction: Key performance indicators in assisted reproductive technologies.

Assisted reproductive technology (ART) has been so widely deployed across the world that over 1% of all births are now ART babies, with even higher percentages in the Nordic countries. As pregnancy rates are limited by technical, population, and inherent limitations of human reproduction, key performance indicators should be defined for all the different facets of ART to measure the efficacy of the procedure.

Key metrics and processes for validating embryo diagnostics.

Embryo diagnostics are somewhat controversial in clinical assisted reproduction technology (ART) practice and remain an active area of investigation. Application of embryo diagnostics holds great potential to raise the standard of clinical care by eliminating futile transfers, allowing highly effective single-embryo transfer, and reducing the probability of clinical loss and ongoing abnormal gestations. These advantages are accompanied by risks, principally the chance that a reproductively competent embryo will be mislabeled and discarded. This would lower the ultimate probability that one or more of the embryos might implant and lead to delivery of a healthy infant. Rigorous validation should be required for embryo diagnostics. Metrics for validation can be divided into three simple areas: analytical validation, determination of clinical predictive values for normal and abnormal test results, and a randomized clinical trial to demonstrate that the selection advantage gained through the diagnostic improves clinical outcomes.

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.

[Polygenic scores: towards designer babies?] / Scores polygéniques : vers l'embryon à la carte ? - Chroniques génomiques.

A new company is offering extensive genetic analysis of embryos during an in vitro fertilisation procedure, allowing the derivation of polygenic scores for several diseases and embryo choice based on these results. Polygenic scores, if properly implemented, can indeed have substantial predictive value, and the possibility of embryo choice based on these data has become real, raising a number of practical and ethical problems. ‡.

Single-Molecule Sequencing: A New Approach for Preimplantation Testing and Noninvasive Prenatal Diagnosis Confirmation of Fetal Genotype.

We investigated the potential of next-generation sequencing (NGS) as an alternative method for preimplantation genetic testing of monogenic disease (PGT-M) with human leukocyte antigen (HLA) matching and for noninvasive prenatal diagnosis follow-up. The case involved parents who were carriers of the Fanconi anemia complementation group G (FANCG) 260delG mutation. After clinical PGT using conventional short tandem repeat and mutation analysis, two euploid disease-free embryos were transferred, resulting in a twin pregnancy. Using the original embryo whole genome amplification products from 10 embryos, NGS confirmed the genotypes of the eight nontransferred embryos for both mutation status and HLA combination. NGS also confirmed that the two transferred embryos, which resulted in a twin pregnancy, were euploid, Fanconi disease free, and HLA matched to their sick sibling. At 15 weeks' gestation, noninvasive prenatal diagnosis of the maternal cell-free DNA determined fetal fractions of 14% and 6.6% for twins 1 and 2, respectively. The maternal plasma FANCG 260delG mutation ratio was measured at 46.2%, consistent with the presence of a carrier fetus and a normal fetus. These findings provide proof of concept that NGS has clinical utility as a safe and effective PGT-M method for embryo genotyping as well as more complex direct HLA matching. In addition, NGS can be used to confirm the original PGT-M and HLA matching embryo results in early pregnancy without the need for invasive prenatal diagnosis.

Noninvasive preimplantation genetic testing for aneuploidy in spent medium may be more reliable than trophectoderm biopsy.

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.

Multiple displacement amplification as the first step can increase the diagnostic efficiency of preimplantation genetic testing for monogenic disease for ß-thalassemia.

AIM: To evaluate whether using multiple displacement amplification (MDA) as the first step can increase the diagnostic efficiency of preimplantation genetic testing for monogenic disease (PGT-M) for ß-thalassemia. METHODS: This is a retrospective cohort study. All included patients underwent PGT-M cycles (n = 307) for ß-thalassemia in our center from January 2014 to February 2018. We divided the patients into two groups based on two different detection methods. For the polymerase chain reaction (PCR) group (n = 115), multiplex nested PCR+ reverse dot blot analysis was performed directly after cell lysis. For the MDA group (n = 192), the whole genomes of single cells were directly amplified using MDA and then examined by singleplex PCR + reverse dot blot for ß-thalassemia. RESULTS: A total of 2315 embryos were tested. The overall diagnostic efficiency of the MDA group was significantly higher than that of the PCR group (96.99% vs 88.15%, P < 0.001). The percentage of embryos available for transfer was significantly higher in the MDA group than in the PCR group (74.28% vs 64.98%, P < 0.001). Furthermore, the carrier embryo rate of the MDA group was significantly higher than that of the PCR group (50.11% vs 35.95%, P < 0.001). CONCLUSION: This study indicates that MDA, as the first step in PGT-M for ß-thalassemia, can increase diagnostic efficiency.

Preimplantation genetic testing for more than one genetic condition: clinical and ethical considerations and dilemmas.

STUDY QUESTION: Which clinical and ethical aspects of preimplantation genetic testing for monogenic disorders or structural rearrangements (PGT-M, PGT-SR) should be considered when accepting requests and counselling couples for PGT when applied for more than one condition (combination-PGT; cPGT-M/SR)? SUMMARY ANSWER: cPGT is a feasible extension of the practice of PGT-M/SR that may require adapting the criteria many countries have in place with regard to indications-setting for PGT-M/SR, while leading to complex choices that require timely counselling and information. WHAT IS KNOWN ALREADY: Although PGT-M/SR is usually performed to prevent transmission of one disorder, requests for PGT-M/SR for more than one condition (cPGT-M/SR) are becoming less exceptional. However, knowledge about implications for a responsible application of such treatments is lacking. STUDY DESIGN, SIZE, DURATION: Retrospective review of all (40) PGT-M/SR applications concerning more than one genetic condition over the period 1995-2018 in the files of the Dutch national PGT centre. This comprises all relevant national data since the start of PGT in the Netherlands. PARTICIPANTS/MATERIALS, SETTING AND METHODS: Data regarding cPGT-M/SR cases were collected by means of reviewing medical files of couples applying for cPGT-M/SR. Ethical challenges arising with cPGT-M/SR were explored against the background of PGT-M/SR regulations in several European countries, as well as of relevant ESHRE-guidance regarding both indications-setting and transfer-decisions. MAIN RESULTS AND THE ROLE OF CHANCE: We report 40 couples applying for cPGT-M/SR of which 16 couples started their IVF treatment. Together they underwent 39 IVF cycles leading to the birth of five healthy children. Of the couples applying for cPGT, 45% differentiated between a primary and secondary condition in terms of perceived severity. In the light of an altered balance of benefits and drawbacks, we argue the 'high risk of a serious condition' standard that many countries uphold as governing indications-setting, should be lowered for secondary conditions in couples who already have an indication for PGT-M/SR. As a consequence of cPGT, professionals will more often be confronted with requests for transferring embryos known to be affected with a condition that they were tested for. In line with ESHRE guidance, such transfers may well be acceptable, on the condition of avoiding a high risk of a child with a seriously diminished quality of life. LIMITATIONS, REASONS FOR CAUTION: We are the first to give an overview of cPGT-M/SR treatments. Retrospective analysis was performed using national data, possibly not reflecting current trends worldwide. WIDER IMPLICATIONS OF THE FINDINGS: Our observations have led to recommendations for cPGT-M/SR that may add to centre policy making and to the formulation of professional guidelines. Given that the introduction of generic methods for genomic analysis in PGT will regularly yield incidental findings leading to transfer requests with these same challenges, the importance of our discussion exceeds the present discussion of cPGT. STUDY FUNDING/COMPETING INTEREST(S): The research for this publication was funded by the Dutch Organization for Health Research and Development (ZonMw), project number: 141111002 (Long term safety, quality and ethics of Preimplantation Genetic Diagnosis). None of the authors has any competing interests to declare.

Assessment of pre-implantation genetic testing for embryo aneuploidies: A SWOT analysis.

The recently re-named pre-implantation genetic testing for determining embryo aneuploidies (PGT-A) is presently very popular although its acceptance by the scientific community is controversial. This approach still encounters drawbacks. This paper uses a SWOT (strengths, weaknesses, opportunities and threats) analysis to discuss salient points to be considered when examining the pre-implantation genetic testing (PGT-A) strategy to gather information from a range of perspectives. One of the strengths associated with the procedure is represented by an increase in implantation rate although data from the highest level of evidence do not support an increase in cumulative pregnancy rates. The current difficulty in the management of mosaicisms represents a weakness of PGT-A. The application of the strategy represents an opportunity to favor the single embryo transfer while other advantages, such as reduction of time to pregnancy and emotional distress are controversial. Potential important threats, at present still undefined, are represented by the biopsy-related damage to the blastocyst and the impact on neonatal and long-term outcomes.

To test or not to test? A framework for counselling patients on preimplantation genetic testing for aneuploidy (PGT-A).

STUDY QUESTION: What is the treatment path and cumulative live birth (CLB) rate from a single oocyte retrieval of patients who intend to pursue PGT-A at the start of an IVF cycle compared to matched controls? SUMMARY ANSWER: The choice of PGT-A at the start of the first IVF cycle decreases the CLB per oocyte retrieval for patients <38 years of age, however patients ≥38 years of age benefit significantly per embryo transfer (ET) when live birth (LB) is evaluated. WHAT IS KNOWN ALREADY: PGT-A has been shown to reduce the practice of transferring multiple embryos and to confer a higher live birth rate per transfer. STUDY DESIGN, SIZE, DURATION: This is a retrospective cohort study from December 2014 to September 2016, involving 600 patients: those intending PGT-A for their first IVF cycle (N = 300) and their matched controls. Post-hoc power calculations (alpha of 0.05, power of 0.80) indicated that our study was powered adequately to demonstrate significant differences in CLB per retrieval and LB per transfer. PARTICIPANTS/MATERIALS, SETTING, METHODS: The study was performed at a large academically affiliated infertility practice where approximately 80% of patients have insurance coverage for fertility care. Patients were identified through electronic medical records, and those who intended to pursue PGT-A at the start of stimulation were assessed. Patients were matched by age, time of oocyte retrieval and oocyte yield to the same number of controls. CLB outcomes per single retrieval, including the fresh and frozen transfers arising from the initial stimulation cycle, were calculated. MAIN RESULTS AND THE ROLE OF CHANCE: PGT-A was not beneficial when CLB rate was assessed per retrieval, however its benefits were significant when LB rate was assessed per transfer. First cycle, <38 year-old patients who intended to have PGT-A had a significantly (P < 0.001) lower CLB rate per oocyte retrieval compared to controls (49.4% vs. 69.1%). Conversely, patients ≥ 38 years in the PGT-A group had similar CLB rates compared to controls per oocyte retrieval, while LB rates per transfer were doubled compared to controls (62.1% vs. 31.7%; P < 0.001). Of the first-cycle PGT-A and control patients, 25.3% and 2.3% failed to achieve a transfer, respectively. LIMITATIONS, REASONS FOR CAUTION: This is not a true intention-to-treat study, due to its retrospective nature. Additionally, the number of patients with two or more previous miscarriages was significantly greater in the PGT-A group as compared to controls, however a sub-analysis showed that this failed to impact outcomes. WIDER IMPLICATIONS OF THE FINDINGS: The findings indicate that PGT-A may be detrimental for those <38 years old undergoing their first IVF cycle. PGT-A has the greatest clinical impact when a transfer is achieved in the ≥38 years old population. This study evaluates the typical treatment path following a patient's choice to pursue PGT-A at the cycle start, and can be used as a guide for counselling patients in relation to age and cycle number. STUDY FUNDING/COMPETING INTEREST(S): None. TRIAL REGISTRATION NUMBER: N/A.