Embryos derived from single pronucleus are suitable for preimplantation genetic testing

OBJECTIVE

To study and compare the preimplantation genetic testing for monogenic disorders (PGT-M) results, and to evaluate the treatment cycle outcomes of embryos derived from a single pronucleus (1PN) vs. two pronuclei (2PN).

DESIGN

A retrospective cohort study from January 2018 to December 2022 involving in vitro fertilization (IVF)-PGT-M treatment cycles.

SETTING

Single, academically affiliated fertility center.

PATIENTS

A total of 244 patients underwent 351 IVF-PGT-M treatment cycles.

INTERVENTION

Embryo biopsy with molecular testing for a monogenic disorder.

MAIN OUTCOME MEASURES

The molecular diagnosis results and clinical outcomes after the transfer of embryos derived from 1PN and 2PN in IVF-PGT-M treatment cycles.

RESULTS

Embryos derived from 1PN have a significantly low developmental potential with a lower rate of embryos that underwent biopsy compared with 2PN-derived embryos; 1PN-derived embryos demonstrated a significantly lower number of blastocysts (24% vs. 37.9%) and top-quality blastocysts (22.3% vs. 48.1%) compared with 2PN-derived embryos. Lower successfully completed and unaffected PGT-M results were achieved in 1PN compared with 2PN-derived embryos (47.1% vs. 65.5% and 18.7% vs. 31.6%, respectively), with significantly higher abnormal molecular results (39.6% vs. 22.7%). The embryo transfer of 24 1PN-derived embryos with no affected genetic disorder resulted in 5 (20.8%) clinical pregnancies and 4 (16.7%) live births (LBs).

CONCLUSIONS

Within the limits of fewer embryos derived from 1PN that yielded unaffected embryos suitable for transfer, the clinical pregnancy and LB rate of 1PN embryos undergoing PGT-M are reassuring. We, therefore, suggest applying PGT-M to embryos derived from 1PN embryos to improve the cumulative clinical pregnancy and LB rates.

Culture time to optimize embryo cell-free DNA analysis for frozen-thawed blastocysts undergoing noninvasive preimplantation genetic testing for aneuploidy

OBJECTIVE

To investigate the ideal time in culture to optimize embryo cell-free deoxyribonucleic acid (cfDNA) analysis in frozen-thawed blastocysts undergoing noninvasive preimplantation genetic testing for aneuploidy (PGT-A). Cell-free DNA is released into the spent blastocyst media (spent media) by the embryo. However, the optimal timing to determine maximal cfDNA in the case of frozen-thawed blastocysts undergoing noninvasive PGT-A remains to be elucidated.

DESIGN

In this prospective observational study, 135 spent media and corresponding whole blastocysts were collected from January 2021 through March 2022.

SETTING

Private fertility clinics.

PATIENTS

Day-5 frozen-thawed blastocysts were cultured for 8 hours (Day-5 Short) or 24 hours (Day-5 Long), whereas day-6 frozen-thawed blastocysts were cultured for 8 hours (Day-6 Short). The spent media and whole blastocysts were then collected for further analysis. Spent media and whole blastocysts were amplified using whole genome amplification and sequenced using next-generation sequencing.

MAIN OUTCOME MEASURES

Informativity and concordance rates between cfDNA in spent media and whole blastocyst DNA were compared according to the different times in culture.

RESULTS

When comparing time in culture, informativity rates for spent media were significantly higher for Day-5 Long and Day-6 Short (>91%) compared with the Day-5 Short group (<60%). A similar trend was observed for cases with and without a previous PGT-A. Regarding blastocyst expansion grade, informativity rates were lower on Day-5 Short compared with Day-5 Long and Day-6 Short, regardless of expansion degree. This decrease was significant for Gardner-grade expansion grades 3, 4, and 5-6. In addition, for a similar time in culture, the grade of expansion did not have an impact on the informativity rates. For concordance rates, no significant differences were observed among the 3 groups. In all cases, concordance rates were 90.5% for Day-5 Short, 93.6% for Day-5 Long, and 92.3% for Day-6 Short. No impact of the expansion grade was observed on concordance rates.

CONCLUSION

Noninvasive PGT-A in frozen-thawed blastocysts yields very high concordance rates with whole blastocysts, possibly limiting the need for invasive PGT-A and making it available for a wider range of patients.

Impact of double trophectoderm biopsy on reproductive outcomes following single euploid blastocyst transfer

OBJECTIVES

To study the effect of double trophectoderm biopsy on clinical outcomes following single euploid blastocyst transfer.

STUDY DESIGN

Retrospective cohort study of 2046 single euploid frozen-thawed blastocyst transfers from January 2015 to June 2022 in a single centre. All patients undergoing a frozen-thawed embryo transfer (FTET) cycle with euploid blastocysts, biopsied for any indication, were included. The outcomes were compared for blastocysts which were biopsied and vitrified once (Group 1, n = 1684), biopsied once but vitrified twice (Group 2, n = 312) and biopsied and vitrified twice (Group 3n = 50). We adjusted for confounders and performed subgroup analysis for PGT-A, PGT-M and PGT-SR cycles. The primary outcome was live birth rate. Secondary outcomes included pregnancy, clinical pregnancy, birthweight and sex ratio.

RESULTS

After adjusting for confounders (previous failed euploid implantations, embryo quality and day of biopsy), embryos which were biopsied twice had lower OR for clinical pregnancy (0.48, CI 0.26-0.88, p = 0.019) and for live birth (0.50 CI 0.27-0.92, p = 0.025) compared to controls. Embryos which were biopsied once but vitrified twice had no different ORs for all reproductive outcomes compared to controls. No significant difference was observed for neonatal birthweight or sex ratio amongst the three groups. This is a retrospective single centre study with inherent bias and results may not be transferable to all settings.

CONCLUSION

This study is the largest to date assessing the outcomes of FTET cycles following double trophectoderm biopsy. The results are in keeping with the existing literature and can be incorporated into patient counselling. Whilst double biopsy seems to adversely impact LBR, it is only one of the many factors that can affect success rates. The subfertility background and embryo characteristics should not be overlooked. This study provides reassuring evidence since double biopsied embryos still result in live births with no difference in sex ratio or birthweight. However, long term follow up of the off-springs is lacking and should be reported in future studies.

Comparative analysis of pregnancy outcomes in preimplantation genetic testing for aneuploidy and conventional in vitro fertilization and embryo transfer: a stratified examination on the basis of the quantity of oocytes and blastocysts from a multicenter randomized controlled trial

OBJECTIVE

To investigate variations in pregnancy outcomes between preimplantation genetic testing for aneuploidy (PGT-A) and conventional in vitro fertilization and embryo transfer (IVF-ET) treatment across distinct groups categorized by oocyte and blastocyst counts. Because the live birth rate (LBR) of assisted reproductive technology treatment is influenced by the number of oocytes and blastocysts retrieved. Our previous study indicated comparable cumulative LBRs (CLBRs) between conventional IVF-ET and PGT-A.

DESIGN

A post hoc exploratory secondary analysis of data from a multicenter randomized controlled trial compared the CLBRs between conventional IVF-ET and PGT-A.

SETTING

Academic fertility centers.

SUBJECTS

A total of 1,212 infertile women with a good prognosis for a live birth after PGT-A or conventional IVF-ET were included.

INTERVENTION

Women underwent PGT-A or conventional IVF-ET.

MAIN OUTCOME MEASURE(S)

Cumulative LBR, cumulative clinical pregnancy loss (CPL) rate, and good birth outcome.

RESULT(S)

In the study, all participants were divided into 4 groups on the basis of quartiles of the number of oocytes retrieved, or blastocysts. There was an interaction between whether to perform PGT-A and the oocyte numbers category on cumulative CPL and biochemical pregnancy loss. Chi-square analysis revealed that the PGT-A group showed a lower cumulative frequency of CPL compared with the IVF-ET group (PGT-A vs. IVF-ET: 5.9% vs. 13.7%; relative risk = 0.430; 95% confidence interval, 0.243-0.763) when the number of oocytes retrieved was <15. Although there was no interaction on CLBR when the retrieved oocyte count ranged from 19-23 (19≤ oocytes <23) the PGT-A group exhibited a lower CLBR than the conventional IVF-ET group (PGT-A vs IVF-ET: 75.6% vs 87.1%; relative risk = 0.868; 95% confidence interval, 0.774-0.973), and the average body weight of newborns from the PGT-A group was approximately 142 g lower than that of the conventional IVF-ET group (PGT-A vs. IVF-ET: 3,334 ± 479 g vs. 3,476 ± 473 g). However, no statistically significant difference in the CLBR was observed between the PGT-A and IVF-ET groups in the other oocyte or blastocyst groups.

CONCLUSION

When the number of retrieved eggs was <15, the PGT-A group exhibited a lower cumulative CPL rate but no higher CLBR than the conventional IVF-ET group.

CLINICAL TRIAL REGISTRATION NUMBER

NCT03118141.

Blastocysts from partial compaction morulae are not defined by their early mistakes

RESEARCH QUESTION

Is partial compaction during morula formation associated with an embryo's developmental ability and implantation potential?

DESIGN

Retrospective analysis of data from 196 preimplantation genetic testing for aneuploidy (PGT-A) cycles. Embryos starting compaction were grouped according to the inclusion or not of all the blastomeres in the forming morula (full compaction or partial compaction). The possible effect of maternal age and ovarian response on compaction was analysed. Morphokinetic characteristics, blastocyst formation rate, morphology and cytogenetic constitution of the obtained blastocysts were compared. Comparisons of reproductive outcomes after the transfer of euploid blastocysts from both groups were established. Finally, in a subset of embryos, the chromosomal constitution concordance of the abandoned cells and the corresponding blastocyst through trophectoderm biopsies was assessed.

RESULTS

A total of 430 embryos failed to include at least one cell during compaction (partial compaction group [49.3%]), whereas the 442 remaining embryos formed a fully compacted morula (full compaction group [50.7%]). Neither female age nor the number of oocytes collected affected the prevalence of partial compaction morulae. Morphokinetic parameters were altered in embryos from partial compaction morulae compared with full compaction. Although an impairment in blastocyst formation rate was observed in partial compaction morulae (57.2% versus 70.8%, P < 0.001), both chromosomal constitution (euploidy rate: partial compaction [38.4%] versus full compaction [34.2%]) and reproductive outcomes (live birth rate: partial compaction [51.9%] versus full compaction [46.2%]) of the obtained blastocysts were equivalent between groups. A high ploidy correlation of excluded cells-trophectoderm duos was observed.

CONCLUSIONS

Partial compaction morulae show a reduced developmental ability compared with full compaction morulae. Resulting blastocysts from both groups, however, have similar euploidy rates and reproductive outcomes. Cell exclusion might be a consequence of a compromised embryo development regardless of the chromosomal constitution of the excluded cells.

How should the best human embryo in vitro be? Current and future challenges for embryo selection

In-vitro fertilization (IVF) aims at overcoming the causes of infertility and lead to a healthy live birth. To maximize IVF efficiency, it is critical to identify and transfer the most competent embryo within a cohort produced by a couple during a cycle. Conventional static embryo morphological assessment involves sequential observations under a light microscope at specific timepoints. The introduction of time-lapse technology enhanced morphological evaluation via the continuous monitoring of embryo preimplantation in vitro development, thereby unveiling features otherwise undetectable via multiple static assessments. Although an association exists, blastocyst morphology poorly predicts chromosomal competence. In fact, the only reliable approach currently available to diagnose the embryonic karyotype is trophectoderm biopsy and comprehensive chromosome testing to assess non-mosaic aneuploidies, namely preimplantation genetic testing for aneuploidies (PGT-A). Lately, the focus is shifting towards the fine-tuning of non-invasive technologies, such as "omic" analyses of waste products of IVF (e.g., spent culture media) and/or artificial intelligence-powered morphologic/morphodynamic evaluations. This review summarizes the main tools currently available to assess (or predict) embryo developmental, chromosomal, and reproductive competence, their strengths, the limitations, and the most probable future challenges.

Optimizing non-invasive preimplantation genetic testing: investigating culture conditions, sample collection, and IVF treatment for improved non-invasive PGT-A results

PURPOSE

This study aimed to optimize the non-invasive preimplantation genetic testing for aneuploidy (niPGT-A) in the laboratory by comparing two collection timing of the spent culture medium (SCM), two embryo rinsing protocols, and the use of conventional insemination instead of intracytoplasmic sperm injection (ICSI).

METHODS

Results of two embryo rinsing methods (one-step vs sequential) and SCM collected on day 5 vs day 6 after retrieval were compared against trophectoderm (TE) biopsies as reference. Results from day 6 SCM in cycles fertilized by conventional insemination were compared with PGT-A using ICSI.

RESULTS

The rate of concordance was higher in day 6 samples than in day 5 samples when the sequential method was used, in terms of total concordance (TC; day 6 vs day 5: 85.0% vs 60.0%, p = 0.0228), total concordance with same sex (TCS, 82.5% vs 28,0%, p < 0.0001), and full concordance with same sex (FCS, 62.5% vs 24.0%, p = 0.0025). The sequential method significantly out-performed the one-step method when SCM were collected on day 6 (sequential vs one-step, TC: 85.0% vs 64.5%, p = 0.0449; TCS: 82.5% vs 54.8%, p = 0.0113; FCS: 62.5% vs 25.8%, p = 0.0021). There was no significant difference in niPGT-A results between cycles fertilized by the conventional insemination and ICSI.

CONCLUSION

We have shown a higher concordance rate when SCM was collected on day 6 and the embryos were rinsed in a sequential manner. Comparable results of niPGT-A when oocytes were fertilized by conventional insemination or ICSI. These optimization steps are important prior to commencement of a randomized trial in niPGT-A.

PGT and deferred embryo transfer: Is blastocyst biopsy more effective than cleaved embryo biopsy?

OBJECTIVE

Blastocyst biopsy has recently been implemented in our laboratory for PGT with a "freeze all" indication. The aim of this study is to compare PGT results between embryos biopsied at the cleaved and embryos biopsied at the blastocyst stage.

STUDY DESIGN

This is a retrospective cohort study conducted from January 2017 to December 2022 in France. All couples with a "freeze all" indication the day of hCG trigerring during the study period were included in the study. Patients were retrospectively assigned in one group of two groups based on the day of embryo biopsy: the cleavage group if a blastomere biopsy was performed on day 3/4 or the blastocyst group if a trophectoderm biopsy was performed on day 5/6. We evaluated and compared the results between the two groups for biological parameters and clinical outcomes.

RESULTS

In total, 325 PGT cycles (291 patients) were included in our study. Frozen-thawed embryo transfer was performed for 285 cycles, 122 in the blastocyst group and 163 in the cleavage group. The number of biopsied embryos per cycle is significantly higher in the cleavage group with a mean of 7.2 ± 4.1 embryos biopsied per cycle vs. 2.9 ± 2.8 embryos in the blastocyst group (p < 0.001). The rate of the useful embryos was similar between the two groups with 14.6 % of frozen healthy embryos among the 1352 cleaved embryos obtained in blastocyst group, compared to 17.1 % in the cleavage group. No significant differences in clinical pregnancy rate per transfer and implantation rate were observed between the blastocyst and cleavage groups (36.4% vs. 40.4 % and 33.1% vs. 33.2 % respectively).

CONCLUSIONS

For "freeze all" PGT cycles, the day of embryo biopsy (cleaved vs blastocyst biopsy) does not impact pregnancy outcomes. Knowing how to perform embryo biopsy at different stages helps to better organize daily laboratory activity and to rescue some undiagnosed embryos after day 3 biopsy.

Multiple embryo manipulations in PGT-A cycles may result in inferior clinical outcomes

RESEARCH QUESTION

Do embryos that undergo a thaw, biopsy and re-vitrification (TBR) for pre-implantation genetic testing for aneuploidy (PGT-A) have different ploidy and transfer outcomes compared with fresh biopsied embryos?

DESIGN

Retrospective cohort study of all embryos that underwent the following procedures: fresh biopsy for PGT-A (fresh biopsy); embryos that were warmed, biopsied for PGT-A and re-vitrified (single biopsy TBR); embryos with a no signal result after initial biopsy that were subsequently warmed, biopsied and re-vitrified (double biopsy TBR). The patients who underwent transfers of those embryos at a single academic institution between March 2013 and December 2021 were also studied.

RESULTS

About 30% of embryos planned for TBR underwent attrition. Euploidy rates were similar after biopsy: fresh biopsy (42.7%); single biopsy TBR (47.5%) (adjusted RR: 0.99, 0.88 to 1.12); and double biopsy TBR 50.3% (adjusted RR: 0.99, 0.80 to 1.21). Ongoing pregnancy over 8 weeks was not statistically significant (double biopsy TBR: 6/19 [31.6%] versus fresh biopsy: 650/1062 [61.2%]) (adjusted RR 0.52, 95% CI 0.26 to 1.03). The miscarriage rate increased (double biopsy TBR: 4/19 [21.1%] versus fresh biopsy: 66/1062 [6.2%])(RR 3.39, 95% CI 1.38 to 8.31). Live birth rate was also lower per transfer for the double biopsy TBR group (double biopsy TBR [18.75%] versus fresh biopsy [53.75%]) (RR 0.35, 95% CI 0.12 to 0.98), though not after adjustment (adjusted RR 0.37, 95% CI 0.13 to 1.09). These differences were not seen when single biopsy TBR embryos were transferred.

CONCLUSIONS

Embryos that undergo TBR have an equivalent euploidy rate to fresh biopsied embryos. Despite that, double biopsy TBR embryos may have impaired transfer outcomes.

Implicit bias in diagnosing mosaicism amongst preimplantation genetic testing providers: results from a multicenter study of 36 395 blastocysts

STUDY QUESTION

Does the diagnosis of mosaicism affect ploidy rates across different providers offering preimplantation genetic testing for aneuploidies (PGT-A)?

SUMMARY ANSWER

Our analysis of 36 395 blastocyst biopsies across eight genetic testing laboratories revealed that euploidy rates were significantly higher in providers reporting low rates of mosaicism.

WHAT IS KNOWN ALREADY

Diagnoses consistent with chromosomal mosaicism have emerged as a third category of possible embryo ploidy outcomes following PGT-A. However, in the era of mosaicism, embryo selection has become increasingly complex. Biological, technical, analytical, and clinical complexities in interpreting such results have led to substantial variability in mosaicism rates across PGT-A providers and clinics. Critically, it remains unknown whether these differences impact the number of euploid embryos available for transfer. Ultimately, this may significantly affect clinical outcomes, with important implications for PGT-A patients.

STUDY DESIGN, SIZE, DURATION

In this international, multicenter cohort study, we reviewed 36 395 consecutive PGT-A results, obtained from 10 035 patients across 11 867 treatment cycles, conducted between October 2015 and October 2021. A total of 17 IVF centers, across eight PGT-A providers, five countries and three continents participated in the study. All blastocysts were tested using trophectoderm biopsy and next-generation sequencing. Both autologous and donation cycles were assessed. Cycles using preimplantation genetic testing for structural rearrangements were excluded from the analysis.

PARTICIPANTS/MATERIALS, SETTING, METHODS

The PGT-A providers were randomly categorized (A to H). Providers B, C, D, E, F, G, and H all reported mosaicism, whereas Provider A reported embryos as either euploid or aneuploid. Ploidy rates were analyzed using multilevel mixed linear regression. Analyses were adjusted for maternal age, paternal age, oocyte source, number of embryos biopsied, day of biopsy, and PGT-A provider, as appropriate. We compared associations between genetic testing providers and PGT-A outcomes, including the number of chromosomally normal (euploid) embryos determined to be suitable for transfer.

MAIN RESULTS AND THE ROLE OF CHANCE

The mean maternal age (±SD) across all providers was 36.2 (±5.2). Our findings reveal a strong association between PGT-A provider and the diagnosis of euploidy and mosaicism. Amongst the seven providers that reported mosaicism, the rates varied from 3.1% to 25.0%. After adjusting for confounders, we observed a significant difference in the likelihood of diagnosing mosaicism across providers (P < 0.001), ranging from 6.5% (95% CI: 5.2-7.4%) for Provider B to 35.6% (95% CI: 32.6-38.7%) for Provider E. Notably, adjusted euploidy rates were highest for providers that reported the lowest rates of mosaicism (Provider B: euploidy, 55.7% (95% CI: 54.1-57.4%), mosaicism, 6.5% (95% CI: 5.2-7.4%); Provider H: euploidy, 44.5% (95% CI: 43.6-45.4%), mosaicism, 9.9% (95% CI: 9.2-10.6%)); and Provider D: euploidy, 43.8% (95% CI: 39.2-48.4%), mosaicism, 11.0% (95% CI: 7.5-14.5%)). Moreover, the overall chance of having at least one euploid blastocyst available for transfer was significantly higher when mosaicism was not reported, when we compared Provider A to all other providers (OR = 1.30, 95% CI: 1.13-1.50). Differences in diagnosing and interpreting mosaic results across PGT-A laboratories raise further concerns regarding the accuracy and relevance of mosaicism predictions. While we confirmed equivalent clinical outcomes following the transfer of mosaic and euploid blastocysts, we found that a significant proportion of mosaic embryos are not used for IVF treatment.

LIMITATIONS, REASONS FOR CAUTION

Due to the retrospective nature of the study, associations can be ascertained, however, causality cannot be established. Certain parameters such as blastocyst grade were not available in the dataset. Furthermore, certain platform-related and clinic-specific factors may not be readily quantifiable or explicitly captured in our dataset. As such, a full elucidation of all potential confounders accounting for variability may not be possible.

WIDER IMPLICATIONS OF THE FINDINGS

Our findings highlight the strong need for standardization and quality assurance in the industry. The decision not to transfer mosaic embryos may ultimately reduce the chance of success of a PGT-A cycle by limiting the pool of available embryos. Until we can be certain that mosaic diagnoses accurately reflect biological variability, reporting mosaicism warrants utmost caution. A prudent approach is imperative, as it may determine the difference between success or failure for some patients.

STUDY FUNDING/COMPETING INTEREST(S)

This work was supported by the Torres Quevedo Grant, awarded to M.P. (PTQ2019-010494) by the Spanish State Research Agency, Ministry of Science and Innovation, Spain. M.P., L.B., A.R.L., A.L.R.d.C.L., N.P.P., M.P., D.S., F.A., A.P., B.M., L.D., F.V.M., D.S., M.R., E.P.d.l.B., A.R., and R.V. have no competing interests to declare. B.L., R.M., and J.A.O. are full time employees of IB Biotech, the genetics company of the Instituto Bernabeu group, which performs preimplantation genetic testing. M.G. is a full time employee of Novagen, the genetics company of Cegyr, which performs preimplantation genetic testing.

TRIAL REGISTRATION NUMBER

N/A.

Preimplantation genetic testing using comprehensive genomic copy number analysis is beneficial for balanced translocation carriers

Balanced chromosomal translocation is one of chromosomal variations. Carriers of balanced chromosomal translocations have an increased risk of spontaneous miscarriage. To avoid the risk, preimplantation genetic testing (PGT) using comprehensive genomic copy number analysis has been developed. This study aimed to verify whether and how embryos from couples in which one partner is a balanced translocation carrier have a higher ratio of chromosomal abnormalities. A total of 894 biopsied trophectoderms (TEs) were obtained from 130 couples in which one partner was a balanced translocation carrier (Robertsonian translocation, reciprocal translocation, or intrachromosomal inversion) and grouped as PGT-SR. Conversely, 3269 TEs from 697 couples who experienced recurrent implantation failure or recurrent pregnancy loss were included in the PGT-A group. The transferable blastocyst ratio was significantly lower in the PGT-SR group, even when bias related to the sample number and patient age was corrected. Subgroup analysis of the PGT-SR group revealed that the transferable blastocyst ratio was higher in the Robertsonian translocation group. Because the PGT-SR group had a higher proportion of untransferable embryos than the PGT-A group, PGT using comprehensive genomic copy number analysis was more beneficial for balanced translocation carriers than for infertility patients without chromosomal translocations. The frequencies of de novo aneuploidies were further analyzed, and the frequency in the PGT-SR group was lower than that in the PGT-A group. Therefore, we could not confirm the existence of interchromosomal effects in this study.

OneGene PGT: comprehensive preimplantation genetic testing method utilizing next-generation sequencing

PURPOSE

Preimplantation genetic testing for monogenic disorders (PGT-M) allows early diagnosis in embryos conceived in vitro. PGT-M helps to prevent known genetic disorders in affected families and ensures that pathogenic variants in the male or female partner are not passed on to offspring. The trend in genetic testing of embryos is to provide a comprehensive platform that enables robust and reliable testing for the causal pathogenic variant(s), as well as chromosomal abnormalities that commonly occur in embryos. In this study, we describe PGT protocol that allows direct mutation testing, haplotyping, and aneuploidy screening.

METHODS

Described PGT protocol called OneGene PGT allows direct mutation testing, haplotyping, and aneuploidy screening using next-generation sequencing (NGS). Whole genome amplification product is combined with multiplex PCR used for SNP enrichment. Dedicated bioinformatic tool enables mapping, genotype calling, and haplotyping of informative SNP markers. A commercial software was used for aneuploidy calling.

RESULTS

OneGenePGT has been implemented for seven of the most common monogenic disorders, representing approximately 30% of all PGT-M indications at our IVF centre. The technique has been thoroughly validated, focusing on direct pathogenic variant testing, haplotype identification, and chromosome abnormality detection. Validation results show full concordance with Sanger sequencing and karyomapping, which were used as reference methods.

CONCLUSION

OneGene PGT is a comprehensive, robust, and cost-effective method that can be established for any gene of interest. The technique is particularly suitable for common monogenic diseases, which can be performed based on a universal laboratory protocol without the need for set-up or pre-testing.

Embryo drop-out rates in preimplantation genetic testing for aneuploidy (PGT-A): a retrospective data analysis from the DoLoRes study

PURPOSE

To evaluate the decline in transferable embryos in preimplantation genetic testing for aneuploidy (PGT-A) cycles due to (a) non-biopsable blastocyst quality, (b) failure of genetic analysis, (c) diagnosis of uniform numerical or structural chromosomal aberrations, and/or (d) chromosomal aberrations in mosaic constitution.

METHODS

This retrospective multicenter study comprised outcomes of 1562 blastocysts originating from 363 controlled ovarian stimulation cycles, respectively, 226 IVF couples in the period between January 2016 and December 2018. Inclusion criteria were PGT-A cycles with trophectoderm biopsy (TB) and next generation sequencing (NGS).

RESULTS

Out of 1562 blastocysts, 25.8% were lost due to non-biopsable and/or non-freezable embryo quality. In 10.3% of all biopsied blastocysts, genetic analysis failed. After exclusion of embryos with uniform or chromosomal aberrations in mosaic, only 18.1% of those originally yielded remained as diagnosed euploid embryos suitable for transfer. This translates into 50.4% of patients and 57.6% of stimulated cycles with no euploid embryo left for transfer. The risk that no transfer can take place rose significantly with a lower number of oocytes and with increasing maternal age. The chance for at least one euploid blastocyst/cycle in advanced maternal age (AMA)-patients was 33.3% compared to 52.1% in recurrent miscarriage (RM), 59.8% in recurrent implantation failure (RIF), and 60.0% in severe male factor (SMF).

CONCLUSIONS

The present study demonstrates that PGT-A is accompanied by high embryo drop-out rates. IVF-practitioners should be aware that their patients run a high risk of ending up without any embryo suitable for transfer after (several) stimulation cycles, especially in AMA patients. Patients should be informed in detail about the frequency of inconclusive or mosaic results, with the associated risk of not having an euploid embryo available for transfer after PGT-A, as well as the high cost involved in this type of testing.

Current Applications and Controversies in Preimplantation Genetic Testing for Aneuploidies (PGT-A) in In Vitro Fertilization

Preimplantation genetic testing for aneuploidy (PGT-A) has evolved over recent years, including improvements in embryo culture, biopsy, transfer, and genetic testing. The application of new comprehensive chromosome screening analysis has improved the accuracy in determining the chromosomal status of the analyzed sample, but it has brought new challenges such as the management of partial aneuploidies and mosaicisms. For the past two decades, PGT-A has been involved in a controversy regarding its efficiency in improving IVF outcomes, despite its widespread worldwide implementation. Understanding the impact of embryo aneuploidy in IVF (in vitro fertilization) should theoretically allow improving reproductive outcomes. This review of the literature aims to describe the impact of aneuploidy in human reproduction and how PGT-A was introduced to overcome this obstacle in IVF (in vitro fertilization). The article will try to analyze and summarize the evolution of the PGT-A in the recent years, and its current applications and limitations, as well as the controversy it generates. Conflicting published data could indicate the lacking value of a single biopsied sample to determine embryo chromosomal status and/or the lack of standardized methods for embryo culture and management and genetic analysis among other factors. It has to be considered that PGT-A may not be a universal test to improve the reproductive potential in IVF patients, rather each clinic should evaluate the efficacy of PGT-A in their IVF program based on their population, skills, and limitations.

Predicting risk of blastocyst aneuploidy among women with previous aneuploid pregnancy loss: a multicenter-data-based multivariable model

STUDY QUESTION

Can blastocyst aneuploidy be predicted for patients with previous aneuploid pregnancy loss (PAPL) and receiving preimplantation genetic testing for aneuploidy (PGT-A)?

SUMMARY ANSWER

Multivariable logistic regression models were established to predict high risk of blastocyst aneuploidy using four identified factors, presenting good predictive performance.

WHAT IS KNOWN ALREADY

Aneuploidy is the most common embryonic chromosomal abnormality leading to pregnancy loss. Several studies have demonstrated a higher embryo aneuploidy rate in patients with PAPL, which has suggested that PGT-A should have benefits in PAPL patients intending to improve their pregnancy outcomes. However, recent studies have failed to demonstrate the efficacy of PGT-A for PAPL patients. One possible way to improve the efficacy is to predict the risk of blastocyst aneuploidy risk in order to identify the specific PAPL population who may benefit from PGT-A.

STUDY DESIGN, SIZE, DURATION

We conducted a multicenter retrospective cohort study based on data analysis of 1119 patients receiving PGT-A in three reproductive medical centers of university affiliated teaching hospitals during January 2014 to June 2020. A cohort of 550 patients who had one to three PAPL(s) were included in the PAPL group. In addition, 569 patients with monogenic diseases without pregnancy loss were taken as the non-PAPL group.

PARTICIPANTS/MATERIALS, SETTING, METHODS

PGT-A was conducted using single nucleotide polymorphism microarrays and next-generation sequencing. Aneuploidy rates in Day 5 blastocysts of each patient were calculated and high-risk aneuploidy was defined as a rate of ≥50%. Candidate risk factors for high-risk aneuploidy were selected using the Akaike information criterion and were subsequently included in multivariable logistic regression models. Overall predictive accuracy was assessed using the confusion matrix, discrimination by area under the receiver operating characteristic curve (AUC), and calibration by plotting the predicted probabilities versus the observed probabilities. Statistical significance was set at P < 0.05.

MAIN RESULTS AND THE ROLE OF CHANCE

Blastocyst aneuploidy rates were 30 ± 25% and 21 ± 19% for PAPL and non-PAPL groups, respectively. Maternal age (odds ratio (OR) = 1.31, 95% CI 1.24-1.39, P < 0.001), number of PAPLs (OR = 1.40, 95% CI 1.05-1.86, P = 0.02), estradiol level on the ovulation trigger day (OR = 0.47, 95% CI 0.30-0.73, P < 0.001), and blastocyst formation rate (OR = 0.13, 95% CI 0.03-0.50, P = 0.003) were associated with high-risk of blastocyst aneuploidy. The predictive model based on the above four variables yielded AUCs of 0.80 using the training dataset and 0.83 using the test dataset, with average and maximal discrepancies of 2.89% and 12.76% for the training dataset, and 0.98% and 5.49% for the test dataset, respectively.

LIMITATIONS, REASONS FOR CAUTION

Our conclusions might not be compatible with those having fewer than four biopsied blastocysts and diminished ovarian reserves, since all of the included patients had four or more biopsied blastocysts and had exhibited good ovarian reserves.

WIDER IMPLICATIONS OF THE FINDINGS

The developed predictive model is critical for counseling PAPL patients before PGT-A by considering maternal age, number of PAPLs, estradiol levels on the ovulation trigger day, and the blastocyst formation rate. This prediction model achieves good risk stratification and so may be useful for identifying PAPL patients who may have higher risk of blastocyst aneuploidy and can therefore acquire better pregnancy outcomes by PGT-A.

STUDY FUNDING/COMPETING INTEREST(S)

This work was supported by the National Natural Science Foundation of China under Grant (81871159). No competing interest existed in the study.

TRIAL REGISTRATION NUMBER

N/A.

PGT-A mosaicism based on NGS intermediate copy numbers: is it time to stop reporting them?

Mosaicism represents a genuine real phenomenon, but its high prevalence and undisclosed clinical significance, stress the burden on genetic counseling and the management of PGT-A results. Even though the assumption of mosaicism from NGS intermediate chromosome copy number profiles may represent a reasonable interpretation, other potential technical reasons, including amplification bias, contamination, biopsy technique, or the analysis algorithms, may constitute alternative explanations. Thresholds confining mosaicism ranges are established according to models employing mixtures of normal and abnormal cells with steady conditions of quantity and quality which are unable to reflect the full extent of variability present in a trophectoderm (TE) biopsy specimen. When the concordance of TE with the ICM is considered, mosaic TE biopsies poorly correlate with the chromosomal status of the remaining embryo, displaying mostly ICM aneuploidy in cases of TE high-range mosaics diagnosis and euploidy when mosaicism grade in TE is less than 50% (low-mid range mosaicism), which implies an evident overestimation of mosaicism results. Indeed, a binary classification of NGS profiles that excludes mosaic ranges, including only euploid and aneuploid diagnosis, provides higher specificity and accuracy in identifying abnormal embryos and discarding them. As intermediate copy number profiles do not represent strong evidence of mosaicism but only an inaccurate and misleading assumption, and considering that no increased risk has been reported in the offspring, until diagnosis specificity is improved and its clinical implications are determined, laboratories should consider limiting predictions to euploid and aneuploid and stop reporting mosaicism.

Blinded rebiopsy and analysis of noneuploid embryos with 2 distinct preimplantation genetic testing platforms for aneuploidy

OBJECTIVE

To determine how often a noneuploid result from a single trophectoderm (TE) biopsy tested with the next-generation sequencing (NGS)-based preimplantation genetic testing for aneuploidy (PGT-A) is concordant with rebiopsies tested with a single-nucleotide polymorphism (SNP) array-based PGT-A platform.

DESIGN

Blinded prospective cohort study.

SETTING

University-affiliated fertility center.

PATIENT(S)

One hundred blastocysts were chosen from donated samples; on TE biopsy with NGS-based PGT-A, 40 had at least one whole chromosome full copy number aneuploidy alone, 20 had a single whole chromosome intermediate copy number ("whole chromosome mosaic"), 20 had a single full segmental aneuploidy (segA), and 20 had a single segmental intermediate copy number ("segmental mosaic").

INTERVENTIONS

Four rebiopsies were collected from each embryo: 3 TE biopsies and the remaining embryo. Each rebiopsy was randomized, blinded, and assessed with an SNP array-based PGT-A platform that combines copy number and allele ratio analyses, without mosaicism reporting.

MAIN OUTCOME MEASURE(S)

Concordance between the NGS result and rebiopsy results and within each embryo's blinded rebiopsy results.

RESULT(S)

Next-generation sequencing-diagnosed whole chromosome aneuploidy (WCA) was reconfirmed in 95% (95% confidence interval [CI], 83%-99%) of embryos; 2 embryos with NGS-diagnosed WCA were called euploid on all conclusive rebiopsies. Among embryos with NGS-diagnosed whole chromosome mosaicism, 35% (95% CI, 15%-59%) were called euploid and 15% (95% CI, 3%-38%) were called whole chromosome aneuploid on all conclusive rebiopsies. A total of 30% (95% CI, 12%-54%) of embryos with NGS-diagnosed segA and 65% (95% CI, 41%-85%) of embryos with NGS-diagnosed segmental mosaicism were called euploid on all conclusive rebiopsies. In total, 13% (95% CI, 6%-25%) of embryos with NGS-diagnosed full copy number aneuploidy and 50% (95% CI, 34%-66%) of embryos with NGS-diagnosed mosaicism had uniformly euploid SNP results. Conversely, all embryos with at least one noneuploid SNP result (n = 72) either had SNP-diagnosed aneuploidy on another rebiopsy from the same embryo or NGS-diagnosed aneuploidy/mosaicism involving the same chromosome.

CONCLUSION(S)

Next-generation sequencing-diagnosed WCA is highly concordant with rebiopsies tested with an SNP array-based PGT-A; however, whole chromosome mosaicism, segA, and segmental mosaicism are less concordant, reinforcing that embryos with these results may have reproductive potential and be suitable for transfer.

A novel embryo biopsy morphological analysis and genetic integrality criterion system significantly improves the outcome of preimplantation genetic testing

PURPOSE

While efforts have been made to establish blastocyst grading systems in the past decades, little research has examined the quality of biopsy specimens. This study is the first to correlate the morphology of biopsied trophectoderm (TE) cells to their quality and subsequent genetic testing results of preimplantation genetic testing (PGT), through an innovative Morphological Analysis and Genetic Integrality Criterion (MAGIC) system.

METHODS

Biopsied TE cells were first evaluated according to the MAGIC procedure, followed by whole-genome amplification (WGA) and library construction, and then sequenced using the Illumina X Ten Platform. Copy number variation (CNV) and allele drop-out (ADO) rates as well as test failure rates were compared and analyzed.

RESULTS

Our data explores the relationship between TE cell morphology and its quality and final genetic testing outcome, which is established based on the MAGIC system. MAGIC guarantees that only high- or good-quality TE cells are used for genetic testing to generate excellent data uniformity and lower ADO rates. Low-quality cells containing biopsied TE cell mass are responsible for the "background noise" of CNV analysis.

CONCLUSION

The MAGIC application has effectively decreased the false-positive mosaicism, hence to ensure the stability and veracity of detection results, to avoid misdiagnoses, and to improve accuracy, as well as to avoid re-biopsy procedures. The study also contributes to understand how the IVF laboratory and the molecular biology laboratory depend on each other to achieve good-quality PGT results, which are clinically relevant for the patients.

The number of prior pregnancy losses does not impact euploidy rates in young patients with idiopathic recurrent pregnancy loss

PURPOSE

Our study aimed to determine the possible factors that might impact the probability of obtaining a euploid blastocyst following intracytoplasmic sperm injection (ICSI) and preimplantation genetic testing for aneuploidy (PGT-A) procedures in idiopathic recurrent pregnancy loss (RPL) patients.

METHODS

This single-center retrospective cohort analysis included 180 oocyte retrieval cycles of 166 women under 35 years old and those diagnosed with idiopathic RPL according to American Society of Reproductive Medicine (ASRM) guidelines. Trophectoderm biopsy and next-generation sequencing (NGS) were the techniques used. Patients were stratified by the number of previous losses (Group A: 2, Group B: 3, and Group C: > 3).

RESULTS

Baseline and embryological characteristics showed no statistically significant differences. The euploidy rate per analyzed blastocyst was comparable within the groups (63.3%, 58.2%, and 58.5%; p = 0.477). Logistic regression analyses confirmed that only the trophectoderm scores of A and B increased the probability of obtaining a euploid embryo [OR: 1.82, 95% CI (1.120-2.956), p: 0.016].

CONCLUSION

It is concluded that there was no correlation between the number of previous losses and the chance of finding at least one euploid embryo in ICSI cycles of women younger than 35 years.

SCM is potential resource for non-invasive preimplantation genetic testing based on human embryos single-cell sequencing

The ongoing development of assisted reproductive technologies has provided hope to individuals struggling with infertility, promising the potential for a healthy pregnancy. One significant innovation in field of pre-implantation genetic screening (PGS) requires the biopsy of embryos or oocytes, which has potential implications for the health and development of the resultant offspring. Therefore, a non-invasive approach to preimplantation genetic screening is highly sought after. The clinical application of non-invasive preimplantation genetic testing (ni-PGT) is currently limited, with its sensitivity and specificity requiring further investigation. In this study, we used 218 human embryos for single-cell whole genome amplification (WGA), along with ni-PGT of blastocoele fluid (BF) and spent culture medium (SCM). Whole blastocyst (WB), trophectoderm biopsy (TB), and inner cell mass (ICM) from embryo biopsies were used as controls to track genomic signal alterations. Our results showed that the overall genome similarity between SCM and ICM was higher than that of BF. Apart from the Y chromosome, both SCM and ICM demonstrated numerous variant sites across other chromosomes.Further categorization of gene variants in these two sample types revealed that missense variants were the most prevalent, single nucleotide polymorphisms were more common than insertions or deletions, and C > T was the dominant single nucleotide variants in both ICM and SCM. Lastly, we found that the mutant genes in SCM and ICM had different biological functions and pathways. This study indicates that SCM provides a more effective source of embryonic DNA for preimplantation genetic screening, offering a novel reference point for genetic screening research.

The Ratio of Serum Progesterone (P4) to the Number of Follicles (P4/follicle) is a More Objective Parameter for Euploidy Rate as Compared to Systemic Progesterone Levels

Does the late follicular phase progesterone (P4) and the P4-to-follicle-ratio affect the ploidy state of the biopsied embryos? A retrospective observational study conducted at ART Fertility Clinics Abu Dhabi and Muscat, including all stimulation cycles performed between January 2015 and December 2019. In total, 975 cycles were considered for this study. Inclusion criteria were ovarian stimulation due to primary/secondary infertility, patient's age between 18 and 45 years, ICSI as fertilization method, and patients undergoing preimplantation genetic testing for aneuploidies (PGT-A). Patients with testicular sperm extraction (TESE) and warmed oocytes were excluded. Our results have shown that progesterone had no effect on the euploid rate (p = 0.371). However, when adding the ratio of P4 to the number of follicles that were bigger than 10 mm in the last scan, a negative effect on the euploid rate (p < 0.05) was observed. This study was able to show that the use of only P4 is unable to predict ploidy outcomes. However, by including the number of follicles > 10 mm, a clear association was observed between P4/Foll ratio and euploid rate per cycle. The use of both parameters could aid clinicians in their decision to trigger a patient or continue stimulation. Further prospective studies are warranted to confirm those results.

Association between a morphokinetic ploidy prediction model risk score and miscarriage and live birth: a multicentre cohort study

OBJECTIVE

To determine whether the aneuploidy risk score from a morphokinetic ploidy prediction model, Predicting Euploidy for Embryos in Reproductive Medicine (PREFER), is associated with miscarriage and live birth outcomes.

DESIGN

Multicentre cohort study.

SETTING

Nine in vitro fertilization clinics in the United Kingdom.

PATIENTS

Data were obtained from the treatment of patients from 2016-2019. A total of 3587 fresh single embryo transfers were included; preimplantation genetic testing for aneuploidy) cycles were excluded.

INTERVENTION

PREFER is a model developed using 8,147 biopsied blastocyst specimens to predict ploidy status using morphokinetic and clinical biodata. A second model using only morphokinetic (MK) predictors was developed, P PREFER-MK. The models will categorize embryos into the following three risk score categories for aneuploidy: "high risk," "medium risk," and "low risk."

MAIN OUTCOME MEASURES

The primary outcomes are miscarriage and live birth. Secondary outcomes include biochemical clinical pregnancy per single embryo transfer.

RESULTS

When applying PREFER, the miscarriage rates were 12%, 14%, and 22% in the "low risk," "moderate risk," and "high risk" categories, respectively. Those embryos deemed "high risk" had a significantly higher egg provider age compared with "low risk," and there was little variation in risk categories in patients of the same age. The trend in miscarriage rate was not seen when using PREFER-MK; however, there was an association with live birth, increasing from 38%-49% and 50% in the "high risk," "moderate risk," and "low risk" groups, respectively. An adjusted logistic regression analysis demonstrated that PREFER-MK was not associated with miscarriage when comparing "high risk" to "moderate risk" embryos (odds ratio [OR], 0.87; 95% confidence interval [CI], 0.63-1.63) or "high risk" to "low risk" embryos (OR, 1.07; 95% CI, 0.79-1.46). An embryo deemed "low risk" by PREFER-MK was significantly more likely to result in a live birth than those embryos graded "high risk" (OR, 1.95; 95% CI, 1.65-2.25).

CONCLUSION

The PREFER model's risk scores were significantly associated with live births and miscarriages. Importantly, this study also found that this model applied too much weight to clinical factors, such that it could no longer rank a patient's embryos effectively. Therefore, a model including only MKs would be preferred; this was similarly associated with live birth but not miscarriage.

Update on preimplantation genetic testing for aneuploidy and outcomes of embryos with mosaic results

Preimplantation genetic testing for aneuploidy (PGT-A) is used as a frequent add-on for in-vitro fertilization (IVF) to improve clinical outcomes. The purpose is to select a euploid embryo following chromosomal testing on embryo biopsies. The current practice includes comprehensive chromosome screening (CCS) technology applied on trophectoderm (TE) biopsies. Despite its widespread use, PGT-A remains a controversial topic mainly because all of the RCTs comprised only good prognosis patients with 2 or more blastocysts available; hence the results are not generalizable to all groups of patients. Furthermore, with the introduction of the highly-sensitive platforms into clinical practice (i.e. next-generation sequencing [NGS]), a result consistent with intermediate copy number surfaced and is termed "Mosaic," consistent with a mixture of euploid and aneuploid cells within the biopsy sample. The optimal disposition and management of embryos with mosaic results is still an open question, as many 'mosaics' generated healthy live births with no identifiable congenital anomalies. The present article provides a complete and comprehensive up-to-date review on PGT-A. It discusses in detail the findings of all the published RCTs on PGT-A with CCS, comments on the subject of "mosaicism" and its current management, and describes the latest technique of non-invasive PGT-A.