When next-generation sequencing-based preimplantation genetic testing for aneuploidy (PGT-A) yields an inconclusive report: diagnostic results and clinical outcomes after re biopsy

The use of preimplantation genetic testing for aneuploidy: a committee opinion

The use of preimplantation genetic testing for aneuploidy (PGT-A) in the United States has been increasing steadily. Moreover, the underlying technology used for 24-chromosome analysis continues to evolve rapidly. The value of PGT-A as a routine screening test for all patients undergoing in vitro fertilization has not been demonstrated. Although some earlier single-center studies reported higher live-birth rates after PGT-A in favorable-prognosis patients, recent multicenter, randomized control trials in women with available blastocysts concluded that the overall pregnancy outcomes via frozen embryo transfer were similar between PGT-A and conventional in vitro fertilization. The value of PGT-A to lower the risk of clinical miscarriage is also unclear, although these studies have important limitations. This document replaces the document of the same name, last published in 2018.

The impact of a second embryo biopsy for preimplantation genetic testing for monogenic diseases (PGT-M) with inconclusive results on pregnancy potential: results from a matched case-control study

PURPOSE

To evaluate whether a second biopsy, following a first diagnostic failure on blastocysts tested for preimplantation genetic testing for monogenic diseases (PGT-M), allows to obtain genetic diagnosis and to what extent this procedure can influence clinical pregnancy and live birth rates compared to the PGT-M process with a successful genetic diagnosis from the first biopsy.

METHODS

Embryos from women who underwent PGT-M in an infertility centre and who had been transferred after two biopsies for genetic analysis (n = 27) were matched in a 1:1 ratio accordingly to women's age (± 1 year) and fertility status (fertile vs infertile), as well as with the study period, with embryos who were transferred after receiving a conclusive PGT result straight after the first biopsy (n = 27). The main evaluated outcome was clinical pregnancy rate following embryo transfers in which healthy embryos were transferred after only one biopsy and those in which an embryo was transferred after being re-biopsied. Live birth rate was the secondary outcome.

RESULTS

Clinical pregnancy rate was 52% (95% CI: 34-69) following the transfer of a single-biopsy blastocyst and 30% (95% CI: 16-48) following the transfer of a re-biopsied blastocyst. The likelihood to have a healthy baby was 33% (95% CI: 19-52) following the transfer of a blastocyst biopsied once and 22% (95% CI: 11-41) following the transfer of a re-biopsied blastocyst.

CONCLUSIONS

The re-biopsy intervention seems to considerably reduce the pregnancy potential of a blastocyst. However, a greater sample size is necessary to clarify this issue definitively.

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.

Opening the black box: why do euploid blastocysts fail to implant? A systematic review and meta-analysis

BACKGROUND

A normal chromosomal constitution defined through PGT-A assessing all chromosomes on trophectoderm (TE) biopsies represents the strongest predictor of embryo implantation. Yet, its positive predictive value is not higher than 50-60%. This gap of knowledge on the causes of euploid blastocysts' reproductive failure is known as 'the black box of implantation'.

OBJECTIVE AND RATIONALE

Several embryonic, maternal, paternal, clinical, and IVF laboratory features were scrutinized for their putative association with reproductive success or implantation failure of euploid blastocysts.

SEARCH METHODS

A systematic bibliographical search was conducted without temporal limits up to August 2021. The keywords were '(blastocyst OR day5 embryo OR day6 embryo OR day7 embryo) AND (euploid OR chromosomally normal OR preimplantation genetic testing) AND (implantation OR implantation failure OR miscarriage OR abortion OR live birth OR biochemical pregnancy OR recurrent implantation failure)'. Overall, 1608 items were identified and screened. We included all prospective or retrospective clinical studies and randomized-controlled-trials (RCTs) that assessed any feature associated with live-birth rates (LBR) and/or miscarriage rates (MR) among non-mosaic euploid blastocyst transfer after TE biopsy and PGT-A. In total, 41 reviews and 372 papers were selected, clustered according to a common focus, and thoroughly reviewed. The PRISMA guideline was followed, the PICO model was adopted, and ROBINS-I and ROB 2.0 scoring were used to assess putative bias. Bias across studies regarding the LBR was also assessed using visual inspection of funnel plots and the trim and fill method. Categorical data were combined with a pooled-OR. The random-effect model was used to conduct the meta-analysis. Between-study heterogeneity was addressed using I2. Whenever not suitable for the meta-analysis, the included studies were simply described for their results. The study protocol was registered at http://www.crd.york.ac.uk/PROSPERO/ (registration number CRD42021275329).

OUTCOMES

We included 372 original papers (335 retrospective studies, 30 prospective studies and 7 RCTs) and 41 reviews. However, most of the studies were retrospective, or characterized by small sample sizes, thus prone to bias, which reduces the quality of the evidence to low or very low. Reduced inner cell mass (7 studies, OR: 0.37, 95% CI: 0.27-0.52, I2 = 53%), or TE quality (9 studies, OR: 0.53, 95% CI: 0.43-0.67, I2 = 70%), overall blastocyst quality worse than Gardner's BB-grade (8 studies, OR: 0.40, 95% CI: 0.24-0.67, I2 = 83%), developmental delay (18 studies, OR: 0.56, 95% CI: 0.49-0.63, I2 = 47%), and (by qualitative analysis) some morphodynamic abnormalities pinpointed through time-lapse microscopy (abnormal cleavage patterns, spontaneous blastocyst collapse, longer time of morula formation I, time of blastulation (tB), and duration of blastulation) were all associated with poorer reproductive outcomes. Slightly lower LBR, even in the context of PGT-A, was reported among women ≥38 years (7 studies, OR: 0.87, 95% CI: 0.75-1.00, I2 = 31%), while obesity was associated with both lower LBR (2 studies, OR: 0.66, 95% CI: 0.55-0.79, I2 = 0%) and higher MR (2 studies, OR: 1.8, 95% CI: 1.08-2.99, I2 = 52%). The experience of previous repeated implantation failures (RIF) was also associated with lower LBR (3 studies, OR: 0.72, 95% CI: 0.55-0.93, I2 = 0%). By qualitative analysis, among hormonal assessments, only abnormal progesterone levels prior to transfer were associated with LBR and MR after PGT-A. Among the clinical protocols used, vitrified-warmed embryo transfer was more effective than fresh transfer (2 studies, OR: 1.56, 95% CI: 1.05-2.33, I2 = 23%) after PGT-A. Lastly, multiple vitrification-warming cycles (2 studies, OR: 0.41, 95% CI: 0.22-0.77, I2 = 50%) or (by qualitative analysis) a high number of cells biopsied may slightly reduce the LBR, while simultaneous zona-pellucida opening and TE biopsy allowed better results than the Day 3 hatching-based protocol (3 studies, OR: 1.41, 95% CI: 1.18-1.69, I2 = 0%).

WIDER IMPLICATIONS

Embryo selection aims at shortening the time-to-pregnancy, while minimizing the reproductive risks. Knowing which features are associated with the reproductive competence of euploid blastocysts is therefore critical to define, implement, and validate safer and more efficient clinical workflows. Future research should be directed towards: (i) systematic investigations of the mechanisms involved in reproductive aging beyond de novo chromosomal abnormalities, and how lifestyle and nutrition may accelerate or exacerbate their consequences; (ii) improved evaluation of the uterine and blastocyst-endometrial dialogue, both of which represent black boxes themselves; (iii) standardization/automation of embryo assessment and IVF protocols; (iv) additional invasive or preferably non-invasive tools for embryo selection. Only by filling these gaps we may finally crack the riddle behind 'the black box of implantation'.

Should embryo rebiopsy be considered a regular strategy to increase the number of embryos available for transfer?

PURPOSE

To investigate whether embryo rebiopsy increases the yield of in vitro fertilization (IVF) cycles.

METHODS

Retrospective study including 18,028 blastocysts submitted for trophectoderm biopsy and preimplantation genetic testing for aneuploidy (PGT-A) between January 2016 and December 2021 in a private IVF center. Out of the 517 embryos categorized as inconclusive, 400 survived intact to the warming procedure, re-expanded, and were suitable for rebiopsy. Of them, 71 rebiopsied blastocysts were transferred. Factors affecting the probability of obtaining an undiagnosed blastocyst and clinical outcomes from blastocysts biopsied once and twice were investigated.

RESULTS

The overall diagnostic rate was 97.1%, with 517 blastocysts receiving inconclusive reports. Several blastocyst and laboratory features, such as the day of the biopsy, the stage of development, and the biopsy methodology, were related to the risk of obtaining an inconclusive diagnosis after PGT-A. A successful diagnosis was obtained in 384 of the rebiopsied blastocysts, 238 of which were chromosomally transferable. A total of 71 rebiopsied blastocysts were transferred, resulting in 32 clinical pregnancies [(clinical pregnancy rate (CPR)=45.1%], 16 miscarriages [(miscarriage rate (MR)=41%], and, until September 2020, 12 live births [(live birth rate (LBR)=23.1%]. A significantly lower LBR and higher MR were obtained after transferring rebiopsied blastocysts compared to those biopsied once.

CONCLUSION

Although an extra round of biopsy and vitrification may cause a detrimental effect on embryo viability, re-analyzing the test-failure blastocysts contributes to increasing the number of euploid blastocysts available for transfer and the LBR.

Impact of Multiple Vitrification-Warming Procedures and Insemination Methods on Pregnancy and Neonatal Outcomes in Preimplantation Genetic Testing for Aneuploidy

This study was to determine whether multiple vitrification-warming procedures and insemination method are associated with pregnancy and neonatal outcomes in preimplantation genetic testing for aneuploidy (PGT-A). This was a retrospective, single-center, observational study of 112 patients who underwent standard PGT-A practice and 154 patients who desired PGT-A for their vitrified unbiopsied blastocysts. A total of 97 euploid blastocysts biopsied and vitrified-warmed once and 117 euploid blastocysts biopsied once but vitrified-warmed twice (83 in vitro fertilization [IVF]-derived and 34 intracytoplasmic sperm injection [ICSI]-derived euploid blastocysts) were transferred. The primary outcome was the blastocyst survival rate for transfer, live birth rate, and neonatal outcomes. The results showed that an additional vitrification-warming procedure on blastocysts resulted in a lower but not statistically different survival rate for transfer. Compared with euploid blastocysts vitrified-warmed once, those vitrified-warmed twice provided statistically similar live birth rate. Neonatal outcomes, including the sex ratio, gestational age, birthweight, preterm birth rate, and low birthweight rate, did not differ between single and double vitrification. No significant differences were observed in rates of blastocyst survival, blastocyst euploid and live birth, and neonatal outcomes resulting from either conventional IVF or ICSI. The neonatal follow-up of babies live-born so far did not report any congenital malformations. In conclusion, an additional vitrification-warming on blastocysts had no detectable adverse impact on clinical outcomes after frozen-thawed single euploid blastocyst transfer in PGT-A cases; and ICSI did not confer any benefit in improving clinical outcomes compared with conventional IVF in cases requiring PGT-A on already vitrified nonbiopsied blastocysts.

Clinical and laboratory key performance indicators in IVF: A consensus between the Italian Society of Fertility and Sterility and Reproductive Medicine (SIFES-MR) and the Italian Society of Embryology, Reproduction and Research (SIERR)

PURPOSE

Infertility is increasing worldwide, and many couples seek IVF. Clinical management and laboratory work are fundamental in the IVF journey. Therefore, the definition of reliable key performance indicators (KPIs) based on clinical and laboratory parameters, is essential for internal quality control (IQC). Laboratory performance indicators have been identified and a first attempt to also determine clinical ones has been recently published. However, more detailed indicators are required.

METHODS

An Italian group of experts in Reproductive Medicine from both public and private clinics on behalf of SIFES-MR and SIERR was established to define IVF indicators to monitor clinical performance.

RESULTS

The working group built a consensus on a list of KPIs, performance indicators (PIs) and recommendation indicators (RIs). When deemed necessary, the reference population was stratified by woman age, response to ovarian stimulation and adoption of preimplantation genetic testing for aneuploidies (PGT-A). Each indicator was scored with a value from 1 to 5 and a weighted average formula - considering all the suggested parameters-was defined. This formula generates a center performance score, indicating low, average, good, or excellent performance.

CONCLUSION

This study is intended to provide KPIs, PIs and RIs that encompass several essential aspects of a modern IVF clinic, including quality control and constant monitoring of clinical and embryological features. These indicators could be used to assess the quality of each center with the aim of improving efficacy and efficiency in IVF.

Double vitrification-warming cycles, coupled with blastocyst biopsy, impair live birth but do not affect neonatal outcomes

OBJECTIVE

To identify whether the transfer of blastocysts that have been vitrified, thawed, biopsied, revitrified, and subsequently rethawed affects clinical outcome and neonatal outcome.

METHODS

A retrospective study was conducted in a single assisted reproduction technology center from September 2016 to March 2021. Women undergoing single frozen euploid blastocysts transfer were stratified into two groups based on number of vitrification-thawing cycles: single vitrification coupled with single biopsy (group A, n = 177) and double vitrification coupled with single biopsy (group B, n = 30). Pregnancy and perinatal outcomes of the two groups were compared.

RESULTS

Clinical pregnancy rates were similar between the two groups. Group B was associated with an increased likelihood of live birth when compared with group A by different multivariable analysis models (model 1: odds ratio, 0.42 [95% confidence interval, 0.18-0.97], P = 0.041; model 2: odds ratio, 0.38 [95% confidence interval, 0.16-0.92], P = 0.033). No major obstetrical complication was reported in the two groups and only one malformation live birth was reported in group A.

CONCLUSION

The procedure of double vitrification-warming cycles, coupled with single biopsy, increases pregnancy loss and ultimately diminishes live birth but does not affect perinatal outcome. Future studies with a larger sample size would help to validate the results.

On the reproductive capabilities of aneuploid human preimplantation embryos

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

Morphological and morphokinetic associations with aneuploidy: a systematic review and meta-analysis

BACKGROUND

A time lapse system (TLS) is utilized in some fertility clinics with the aim of predicting embryo viability and chance of live birth during IVF. It has been hypothesized that aneuploid embryos display altered morphokinetics as a consequence of their abnormal chromosome complement. Since aneuploidy is one of the fundamental reasons for IVF failure and miscarriage, attention has focused on utilizing morphokinetics to develop models to non-invasively risk stratify embryos for ploidy status. This could avoid or reduce the costs associated with pre-implantation genetic testing for aneuploidy (PGT-A). Furthermore, TLS have provided an understanding of the true prevalence of other dysmorphisms. Hypothetically, the incorporation of morphological features into a model could act synergistically, improving a model's discriminative ability to predict ploidy status.

OBJECTIVE AND RATIONALE

The aim of this systematic review and meta-analysis was to investigate associations between ploidy status and morphokinetic or morphological features commonly denoted on a TLS. This will determine the feasibility of a prediction model for euploidy and summarize the most useful prognostic markers to be included in model development.

SEARCH METHODS

Five separate searches were conducted in Medline, Embase, PubMed and Cinahl from inception to 1 July 2021. Search terms and word variants included, among others, PGT-A, ploidy, morphokinetics and time lapse, and the latter were successively substituted for the following morphological parameters: fragmentation, multinucleation, abnormal cleavage and contraction. Studies were limited to human studies.

OUTCOMES

Overall, 58 studies were included incorporating over 40 000 embryos. All except one study had a moderate risk of bias in at least one domain when assessed by the quality in prognostic studies tool. Ten morphokinetic variables were significantly delayed in aneuploid embryos. When excluding studies using less reliable genetic technologies, the most notable variables were: time to eight cells (t8, 1.13 h, 95% CI: 0.21-2.05; three studies; n = 742; I2 = 0%), t9 (2.27 h, 95% CI: 0.5-4.03; two studies; n = 671; I2 = 33%), time to formation of a full blastocyst (tB, 1.99 h, 95% CI 0.15-3.81; four studies; n = 1640; I2 = 76%) and time to expanded blastocyst (tEB, 2.35 h, 95% CI: 0.06-4.63; four studies; n = 1640; I2 = 83%). There is potentially some prognostic potential in the degree of fragmentation, multinucleation persisting to the four-cell stage and frequency of embryo contractions. Reverse cleavage was associated with euploidy in this meta-analysis; however, this article argues that these are likely spurious results requiring further investigation. There was no association with direct unequal cleavage in an embryo that progressed to a blastocyst, or with multinucleation assessed on Day 2 or at the two-cell stage. However, owing to heterogeneous results and poor-quality evidence, associations between these morphological components needs to be investigated further before conclusions can be reliably drawn.

WIDER IMPLICATIONS

This first systematic review and meta-analysis of morphological and morphokinetic associations with ploidy status demonstrates the most useful morphokinetic variables, namely t8, t9 and tEB to be included in future model development. There is considerable variability within aneuploid and euploid embryos making definitively classifying them impossible; however, it is feasible that embryos could be prioritized for biopsy. Furthermore, these results support the mechanism by which algorithms for live birth may have predictive ability, suggesting aneuploidy causes delayed cytokinesis. We highlight significant heterogeneity in our results secondary to local conditions and diverse patient populations, therefore calling for future models to be robustly developed and tested in-house. If successful, such a model would constitute a meaningful breakthrough when accessing PGT-A is unsuitable for couples.

Clinical re-biopsy of segmental gains-the primary source of preimplantation genetic testing false positives

PURPOSE

Does re-biopsy of blastocysts classified as abnormal (ABN) due to segmental aneuploidy (SA) have clinical utility?

METHODS

The live birth (LB) outcomes of mosaic SAs, compared to other categories, were determined after transfer of 3084 PGT-A tested blastocysts. An initial 12-month trial thawed 111 blastocysts classified as ABN due to a SA for clinical re-biopsy, with an additional 58 from a subsequent 16-month revised protocol. Where re-biopsy failed to corroborate the original classification, blastocysts were reported as mosaic and suitable for clinical use.

RESULTS

Segmental mosaics had a LB rate (54.1%) which was indistinguishable from that of euploid (53.7%). Numeric mosaics had statistically significant (P < 0.05) reduced LB rates compared to euploid, with high-level numerics (19.2%) also exhibiting a significant reduction compared to low level (42.3%). Of the initial 111 blastocysts with SAs, 85 could be re-biopsied. Segmental gains became suitable for re-biopsy at a high rate (90.9%), with 84.2% (16/19) of these reclassified as mosaic. Only 73.0% of deletions and complex changes were suitable for re-biopsy, of which 73.0% (46/63) were confirmed ABN. The subsequent 16-month period primarily focused on gains, confirming the high rate at which they can be reclassified as clinically useable.

CONCLUSIONS

Blastocysts harboring mosaic segmental duplications, rather than SAs in general, are the primary source of false-positive PGT-A results and represent a category with a LB rate similar to that of euploid. A high degree of confidence in the reliability of PGT-A results can be maintained by performing confirmatory clinical TE biopsies.

Preimplantation genetic testing for aneuploidy (PGT-A)-a single-center experience

PURPOSE

The aim of this study was to determine the prevalence and nature of human embryonic aneuploidy based on the preimplantation genetic testing for aneuploidy (PGT-A), the distribution of aneuploidy across the individual chromosomes, and their relationship to maternal age.

METHODS

This is a retrospective cohort study conducted at a single center. The study includes subjects who opted for PGT-A in their in vitro fertilization (IVF) cycle from 2016 to 2020. PGT-A was performed on 1501 embryos from 488 patients in 535 cycles. PGT-A was performed using NGS-based technique on Ion Torrent PGM (Life Technologies). Analysis was performed to determine the (i) frequency of the aneuploidy, (ii) the chromosome most commonly affected, (iii) relationship between maternal age and the rate of aneuploidy, and (iv) incidence of segmental aneuploidy.

RESULTS

The overall frequency of aneuploidy was observed to be 46.8%. The incidence of aneuploidy rate was ~ 28% at maternal age < 30 years which steadily increased to ~ 67% in women above 40 years. High frequency of aneuploidy was observed in chromosomes 16, 22, 21, and 15. Segmental abnormalities, involving loss or gain of chromosomal fragments, were observed at a frequency of 5.3%, and highest incidence of segmental gain was observed on the q-arm of chromosome 9.

CONCLUSION

The study provides important information regarding the frequency of the aneuploidy in IVF cohort and the most frequent chromosomal abnormality. The study further emphasizes the relationship between maternal age and aneuploidy. This study has important implications which help clinicians and genetic counselors in providing information in patient counseling.

Live birth rate following a euploid blastocyst transfer is not affected by double vitrification and warming at cleavage or blastocyst stage

PURPOSE

To compare reproductive outcomes following a euploid embryo transfer, between those embryos vitrified-warmed twice to those vitrified-warmed once.

METHODS

We retrospectively analysed 694 single euploid frozen embryo transfer cycles following preimplantation genetic testing for aneuploidy (PGT-A). For cycles in group 1 (N = 451), embryos were biopsied for PGT-A at blastocyst stage and vitrified. For cycles in group 2 (N = 146), embryos were vitrified at blastocyst stage, before being warmed and biopsied for PGT-A and vitrified again. For cycles in group 3 (N = 97), embryos were vitrified on day-3, before being warmed, cultured to day-5 and biopsied for PGT-A and re-vitrified.

RESULTS

The pregnancy, clinical pregnancy and livebirth rate in group 2 were not statistically different to group 1 (pregnancy rate, adjusted OR 1.09, 95% CI 0.62-1.91; clinical pregnancy, aOR 0.89, 95% CI 0.58-1.37; live birth rate, aOR 0.85, 95% CI 0.56-1.28). There was also no significant difference between group 3 and group 1, with similar pregnancy rate (aOR 1.22, 95% CI 0.74-1.99), clinical pregnancy rate (aOR 1.21, 95% CI 0.75-1.96) and live birth rate (aOR 1.15, 95% CI, 0.73-1.80). There was no significant difference in miscarriage rates between all three groups. The age at the oocyte collection, embryo quality and day of biopsy were associated with pregnancy, clinical pregnancy and live birth rate.

CONCLUSION

This study suggests that vitrifying and warming embryos twice at blastocyst or at cleavage and then blastocyst stage, can lead to similar reproductive outcomes to embryos vitrified-warmed once, after a single euploid embryo transfer.

Oocyte quality and embryo selection strategies: a review for the embryologists, by the embryologists

With the advance of assisted reproduction techniques, and the trend towards blastocyst culture and single embryo transfer, gamete and embryo assessment have gained greater importance in ART treatment. Embryo quality depends mainly on gamete quality and culture conditions. Oocyte maturity identification is necessary in order to plan fertilization timing. Mature oocytes at the metaphase II stage show a higher fertilization rate compared to immature oocytes. Morphology assessment is a critical yet challenging task that may serve as a good prognostic tool for future development and implantation potential if done effectively. Various grading systems have been suggested to assess embryos at pronuclear, cleavage, and blastocyst stages. By identifying the embryo with the highest implantation potential, it is possible to reduce the number of embryos transferred without compromising the chances of a successful pregnancy. Apart from the conventional morphology assessment, there are several invasive or non-invasive methods for embryo selection such as preimplantation genetic testing, morphokinetics, proteomics, metabolomics, oxygen consumption, and measurement of oxidative stress in culture medium. Morphokinetics is a method based on time-lapse technology and continuous monitoring of embryos. In this review, we aim to describe and compare the most effective and widely used methods for gamete and embryo assessment as well as embryo selection.

The concordance rates of an initial trophectoderm biopsy with the rest of the embryo using PGTseq, a targeted next-generation sequencing platform for preimplantation genetic testing-aneuploidy

OBJECTIVE

To determine how often the results of a single trophectoderm (TE) biopsy tested by PGTseq, a targeted next-generation sequencing preimplantation genetic testing for aneuploidy technology, reflect the biology of the rest of the embryo.

DESIGN

Blinded prospective cohort study.

SETTING

University-affiliated private practice.

PATIENT(S)

A total of 300 blastocysts were donated; 113 of these embryos were euploid; 163 embryos possessed at least one whole chromosome aneuploidy; and 24 embryos were negative for whole chromosome aneuploidy but possessed at least one secondary finding on initial TE biopsy.

INTERVENTION(S)

All blastocysts underwent rebiopsy and preimplantation genetic testing for aneuploidy on the PGTseq platform.

MAIN OUTCOME MEASURE(S)

Partial concordance rate per embryo, total concordance rate per embryo, and total concordance rate per chromosomal event.

RESULT(S)

An initial TE biopsy result of euploidy or whole chromosome aneuploidy was reconfirmed in >99% of rebiopsied samples, affirming that meiotic errors are manifested in almost the entire embryo. In contrast, results of whole chromosome or segmental mosaicism were confirmed in 15%-18% of subsequent rebiopsies, suggesting that mitotic events are only sporadically seen throughout the embryo. Segmental aneuploidy was confirmed in 56.6% of rebiopsied samples, identifying a mixed meiotic and mitotic etiology for such abnormalities.

CONCLUSION(S)

A euploid or aneuploid result on the PGTseq platform is highly concordant with the rest of the embryo's ploidy status. The rarer confirmation of whole chromosome mosaic and segmental mosaic results suggest that these mosaics are suitable for embryo transfer. Segmental aneuploidy, with higher concordance rates throughout the embryo, may represent a different biologic etiology compared to mosaic embryos.

Multiple vitrification-warming and biopsy procedures on human embryos: clinical outcome and neonatal follow-up of children

STUDY QUESTION

Does double vitrification and warming of human blastocysts having undergone biopsy once or twice have an impact on the clinical outcome?

SUMMARY ANSWER

The clinical pregnancy rate obtained with double vitrification single biopsy blastocysts was comparable to that obtained with single vitrification single biopsy blastocysts in our center in the same time period (46%; 2016-2018), whereas that obtained with double-vitrified double-biopsied blastocysts seemed lower and will need further study.

WHAT IS KNOWN ALREADY

Genetic testing on cryopreserved unbiopsied embryos involves two cryopreservation procedures. Retesting of failed/inconclusive-diagnosed blastocysts inevitably involves a second round of biopsy and a second round of vitrification as well. To what extent this practice impacts on the developmental potential of blastocysts has been studied to a limited extent so far and holds controversy. Additionally, the obstetrical/perinatal outcome after the transfer of double-vitrified/single or double-biopsied blastocysts is poorly documented.

STUDY DESIGN, SIZE, DURATION

This retrospective observational study included 97 cycles of trophectoderm biopsy and preimplantation genetic testing (PGT) on vitrified-warmed embryos followed by a second round of vitrification between March 2015 and December 2019.

PARTICIPANTS/MATERIALS, SETTING, METHODS

In 36 warming cycles, no biopsy was performed on the embryos before the first vitrification (single biopsy group). In 61 warming cycles, the embryos had been biopsied on Day 3 (n = 4) or on Day 5/6 (n = 57) before the first vitrification (double biopsy group). A second biopsy was mostly indicated in cycles of failed or inconclusive diagnosis at the first biopsy. Two cycles involved a more specific mutation test for X-linked diseases on male embryos and one cycle involved testing for a second monogenic indication supplementary to a previously tested reciprocal translocation. Post-warming suitability for biopsy, availability of genetically transferable embryos and clinical outcome of subsequent frozen-thawed embryo transfer (FET) cycles were reported. Neonatal follow-up of the children was included.

MAIN RESULTS AND THE ROLE OF CHANCE

In total, 91 cleavage-stage embryos and 154 blastocysts were warmed, of which 34 (37.4%) and 126 (81.8%), respectively, were of sufficient quality to undergo trophectoderm biopsy and were subsequently vitrified for a second time. Out of these, 92 underwent biopsy for the first time (single biopsy), whereas 68 underwent a second biopsy (double biopsy). After diagnosis, 77 blastocysts (48.1%) were revealed to be genetically transferable (44 in the single biopsy group and 33 in the double biopsy group). In 46 warming cycles, 51 blastocysts were warmed and 49 survived this second warming procedure (96.0%). Subsequently, there were 45 FET cycles resulting in 27 biochemical pregnancies and 18 clinical pregnancies with fetal heartbeat (40.0% per FET cycle: 44.0% in the single biopsy group and 35.0% in the double biopsy group, P = 0.54). Thirteen singletons were born (eight in the single biopsy group and five in the double biopsy group), while three pregnancies were ongoing. A total of 26 embryos (13 in each group) remain vitrified and have the potential to increase the final clinical pregnancy rate. The neonatal follow-up of the children born so far is reassuring.

LIMITATIONS, REASONS FOR CAUTION

This is a small retrospective cohort, thus, the implantation potential of double vitrification double biopsy blastocysts, as compared to double vitrification single biopsy blastocysts and standard PGT (single vitrification, single biopsy), certainly needs further investigation. Although one could speculate on birthweight being affected by the number of biopsies performed, the numbers in this study are too small to compare birthweight standard deviation scores in singletons born after single or double biopsy.

WIDER IMPLICATIONS OF THE FINDINGS

PGT on vitrified-warmed embryos, including a second vitrification-warming step, results in healthy live birth deliveries, for both single- and double-biopsied embryos. The neonatal follow-up of the 13 children born so far did not indicate any adverse effect. The present study is important in order to provide proper counseling to couples on their chance of a live birth per initial warming cycle planned and concerning the safety issue of rebiopsy and double vitrification.

STUDY FUNDING/COMPETING INTEREST(S)

None.

TRIAL REGISTRATION NUMBER

N/A.

Complex mosaic blastocysts after preimplantation genetic testing: prevalence and outcomes after re-biopsy and re-vitrification

RESEARCH QUESTION

What is the incidence of complex mosaic in preimplantation genetic testing (PGT) blastocysts and can it be managed in clinical practice?

DESIGN

A retrospective study of PGT cycles conducted between January 2018 and October 2019 at a single centre. Biopsies of blastocysts were collected and analysed by next-generation sequencing (NGS). Complex mosaic blastocysts were defined as those with three or more mosaic chromosomes. The cryopreserved complex mosaic blastocysts underwent a second round of biopsy, NGS analysis and vitrification. The euploid blastocysts identified by the re-biopsy were warmed again for embryo transfer. The main outcomes included the prevalence of the complex mosaic and the ongoing pregnancy rate.

RESULTS

The prevalence of the complex mosaic was 2.4% (437/17,979). The prevalence of the complex mosaic was not associated with maternal age and morphological quality. A total of 89 complex mosaic blastocysts underwent re-biopsy and 96.6% (86/89) survived the first warming. For the re-biopsy samples, 61.6% (53/86) were euploid. The poor-quality blastocysts had higher rates of aneuploidy compared with good-quality blastocysts. The survival rate for blastocysts undergoing the second warming was 100% (18/18) and resulted in an ongoing pregnancy rate of 38.9% (7/18) as well as the birth of six healthy infants.

CONCLUSION

Re-biopsy may rescue blastocysts with development potential for transfer and improve the cumulative pregnancy rate per stimulation cycle in patients containing complex mosaic blastocysts.

Chromosomal analysis for embryos from balanced chromosomal rearrangement carriers using next generation sequencing

We aimed to use next generation sequencing (NGS) to investigate chromosomal abnormalities in blastocyst trophectoderm (TE) samples, and reproductive outcomes with the different types of chromosomal rearrangements (CR) and for each sex of CR carrier. A total of 1189 blastocyst TE samples were evaluated using NGS to detect chromosomal unbalanced translocations as well as aneuploidy, including blastocytes from 637 blastocysts from carriers of balanced CR and 552 blastocysts from carriers of normal chromosomes. The optimal embryos had lower chromosomal abnormality rates compared to the poor-quality embryos. The experimental group had significantly reduced rates of normal embryos and euploidy, and higher rates of total abnormalities, aneuploidy and unbalanced chromosomal aberrations. Carriers of reciprocal translocations had a reduced rate of normal embryos and an increased percentage of embryos with total abnormalities and unbalanced chromosomal aberrations compared with carriers of Robertsonian translocations. Couples with female carriers of chromosomal abnormalities had significantly reduced rates of normal embryos and euploidy, and a higher percentage of embryos with total abnormalities, aneuploidy, and unbalanced chromosomal aberrations compared with couples of male carriers. Our preimplantation genetic testing (PGT) study identified higher rates of chromosomal abnormalities, including chromosomal unbalanced translocations and aneuploidy, in blastocysts from CR carriers, especially from the female carriers, in a Chinese population. The PGT cycles successfully improved clinical outcomes by increasing the fertilization rate and reducing the early spontaneous abortion rate compared with the in vitro fertilization and intracytoplasmic sperm injection cycles, especially for CR carriers.

Multiple cryopreservation-warming cycles, coupled with blastocyst biopsy, negatively affect IVF outcomes

RESEARCH QUESTION

Do multiple cryopreservation-warming cycles, coupled with blastocyst biopsy, negatively affect IVF outcomes?

DESIGN

Patients undergoing IVF with homologous single embryo transfer, and who underwent trophectoderm biopsy for preimplantation genetic testing for aneuploidy (PGT-A) between 2013 and 2017, were divided into three groups based on degree of embryonic micromanipulation: once-biopsied, once-cryopreserved (group BC, n = 2603), once-biopsied, twice-cryopreserved (group CBC, n = 95) and twice-biopsied, twice-cryopreserved (group BCBC, n = 15). The primary outcome was live birth; secondary outcomes included positive serum pregnancy test, clinical pregnancy and miscarriage.

RESULTS

Group CBC had a significantly lower chance of live birth (adjusted RR 0.57, 95% CI 0.41 to 0.79) and clinical pregnancy (adjusted RR 0.67, 95% CI 0.53 to 0.85) compared with group BC. Miscarriage rates were similar between groups BC and CBC (adjusted RR 1.3, 95% CI 0.64 to 2.7).

CONCLUSIONS

Multiple cryopreservation-warming cycles, coupled with blastocyst biopsy, negatively affect IVF outcomes. Although PGT-A is thought to improve reproductive outcomes on a per transfer basis, caution must be exercised in counselling patients on the possibility of diminishing returns owing to further embryonic micromanipulation after an embryo has been cryopreserved.

Successful four-factor preimplantation genetic testing: α- and β-thalassemia, human leukocyte antigen typing, and aneuploidy screening

Our study established an effective next-generation sequencing (NGS) protocol for four-factor preimplantation genetic testing (PGT) using  α- and β-thalassemia, human leukocyte antigen (HLA) typing, and aneuploidy screening. Three couples, in whom both partners were α- and β-double thalassemia carriers, underwent PGT between 2016 and 2018. These individuals sought an opportunity for hematopoietic stem cell transplantation to save their children from β-thalassemia major. A total of 35 biopsied trophectoderm samples underwent multiple displacement amplification (MDA). PGT for α- and β-thalassemia and HLA typing were performed on MDA products using NGS-based single-nucleotide polymorphism (SNP) haplotyping. Although two samples failed MDA, 94.3% (33/35) of samples were successfully amplified, achieving conclusive PGT results. Furthermore, 51.5% (17/33) of the embryos were diagnosed as unaffected non-carriers or carriers. Of the 17 unaffected embryos, nine (52.9%) were tested further  and identified as euploid via NGS-based aneuploid screening, in which five had HLA types matching affected children. One family did not achieve any unaffected euploid embryos. The two other families transferred HLA-matched and unaffected euploid embryos, resulting in two healthy 'savior babies.' NGS-PGT results were confirmed in prenatal diagnosis. Therefore, NGS-SNP was effective in performing PGT for multipurpose detection within a single PGT cycle.

The dawn of the future: 30 years from the first biopsy of a human embryo. The detailed history of an ongoing revolution

Following early studies showing no adverse effects, cleavage stage biopsy by zona drilling using acid Tyrode's solution, and removal of single blastomeres for preimplantation genetic testing (PGT) and identification of sex in couples at risk of X-linked disease, was performed by Handyside and colleagues in late 1989, and pregnancies reported in 1990. This method was later used for specific diagnosis of monogenic conditions, and a few years later also for chromosomal structural and/or numerical impairments, thereby establishing a valuable alternative option to prenatal diagnosis. This revolutionary approach in clinical embryology spread worldwide, and several other embryo biopsy strategies developed over three decades in a process that is still ongoing. The rationale of this narrative review is to outline the different biopsy approaches implemented across the years in the workflow of the IVF clinics that provided PGT: their establishment, the first clinical experiences, their downsides, evolution, improvement and standardization. The history ends with a glimpse of the future: minimally/non-invasive PGT and experimental embryo micromanipulation protocols. This grand theme review outlines a timeline of the evolution of embryo biopsy protocols, whose implementation is increasing worldwide together with the increasing application of PGT techniques in IVF. It represents a vade mecum especially for the past, present and upcoming operators and experts in this field to (re)live this history from its dawn to its most likely future.

Consistency in rates of diagnosis of embryonic mosaicism, segmental abnormalities, and "no call" results among experienced embryologists performing preimplantation genetic testing for aneuploidy

OBJECTIVE

To determine whether differences exist in rates of subchromosomal abnormalities, mosaicism, and "no call" results among embryologists performing and loading trophectoderm biopsies for preimplantation genetic testing for aneuploidy (PGT-A).

DESIGN

Retrospective cohort.

SETTING

Large infertility center.

PATIENTS

All patients undergoing in vitro fertilization with PGT-A.

INTERVENTIONS

The NexCCS next generation sequencing platform was used for PGT-A. The χ2 testing assessed differences in rates of primary outcomes between embryologists. Intraclass correlation coefficients evaluated inter-embryologist reliability in rates of abnormal and no call results. Median absolute performance difference (MAPD) scores, which quantify the impact of technical variation on analytical performance, were averaged for individual embryologists. Analysis of variance assessed differences in mean MAPD scores.

MAIN OUTCOME MEASURES

Interoperator variability in rates of mosaic, segmental, and no call results.

RESULTS

Four embryologists performed 30,899 biopsies and 6 embryologists loaded specimens into designated tubes. Among individuals performing trophectoderm sampling, rates of mosaicism were 4.3% to 6.1%, segmental errors were 9.0% to 10.7%, and inconclusive results were 1.1% to 2.9%. For those loading, the incidence of mosaicism was 4.2% to 5.9%, subchromosomal abnormalities was 9.7% to 10.4%, and no call results was 1.2% to 2.2%. The intraclass correlation coefficient was 0.978 for embryologists performing biopsies and 0.981 for those loading. Differences in mean MAPD scores were within 0.6% and 0.2% of each other for doing biopsies and loading embryologists, respectively.

CONCLUSIONS

Rates of mosaicism, segmental, and no call PGT-A results are consistent among experienced embryologists. Due to the large sample size included, differences within 1% of the mean were deemed clinically irrelevant despite statistical significance.