Blastocysts can be rebiopsied for preimplantation genetic diagnosis and screening

Impacts of double biopsy and double vitrification on the clinical outcomes following euploid blastocyst transfer: a systematic review and meta-analysis

STUDY QUESTION

Compared to the 'single biopsy + single vitrification' approach, do 'double biopsy + double vitrification' or 'single biopsy + double vitrification' arrangements compromise subsequent clinical outcomes following euploidy blastocyst transfer?

SUMMARY ANSWER

Both 'double biopsy + double vitrification' and 'single biopsy + double vitrification' led to reduced live birth/ongoing pregnancy rates and clinical pregnancy rates.

WHAT IS KNOWN ALREADY?

It is not uncommon to receive inconclusive results following blastocyst biopsy and preimplantation genetic testing for aneuploidy (PGT-A). Often these blastocysts are warmed for re-test after a second biopsy, experiencing 'double biopsy + double vitrification'. Furthermore, to achieve better workflow, IVF laboratories may choose to routinely vitrify all blastocysts and schedule biopsy at a preferred timing, involving 'single biopsy + double vitrification'. However, in the current literature, there is a lack of systematic evaluation of both arrangements regarding their potential clinical risks in reference to the most common 'single biopsy + single vitrification' approach.

STUDY DESIGN, SIZE, DURATION

A systematic review and meta-analysis were performed, with the protocol registered in PROSPERO (CRD42023469143). A search in PUBMED, EMBASE, and the Cochrane Library for relevant studies was carried out on 30 August 2023, using the keywords 'biopsy' and 'vitrification' and associated variations respectively. Only studies involving frozen transfers of PGT-A tested euploid blastocysts were included, with those involving PGT-M or PGT-SR excluded.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Study groups included blastocysts having undergone 'double biopsy + double vitrification' or 'single biopsy + double vitrification', with a 'single biopsy + single vitrification' group used as control. The primary outcome was clinical pregnancy, while secondary outcomes included live birth/ongoing pregnancy, miscarriage, and post-warming survival rates. Random effects meta-analysis was performed with risk ratios (RR) and 95% CIs were used to present outcome comparisons.

MAIN RESULTS AND THE ROLE OF CHANCE

A total of 607 records were identified through the initial search and nine studies (six full articles and three abstracts) were eventually included. Compared to 'single biopsy + single vitrification', 'double biopsy + double vitrification' was associated with reduced clinical pregnancy rates (six studies, n = 18 754; RR = 0.80, 95% CI = 0.71-0.89; I2 = 0%) and live birth/ongoing pregnancy rates (seven studies, n = 20 964; RR = 0.72, 95% CI = 0.63-0.82; I2 = 0%). However, no significant changes were seen in miscarriage rates (seven studies, n = 22 332; RR = 1.40, 95% CI = 0.92-2.11; I2 = 53%) and post-warming survival rates (three studies, n = 13 562; RR = 1.00, 95% CI = 0.99-1.01; I2 = 0%) following 'double biopsy + double vitrification'. Furthermore, 'single biopsy + double vitrification' was also linked with decreased clinical pregnancy rates (six studies, n = 13 284; RR = 0.84, 95% CI = 0.76-0.92; I2 = 39%) and live birth/ongoing pregnancy rates (seven studies, n = 16 800; RR = 0.79, 95% CI = 0.69-0.91; I2 = 70%), and increased miscarriage rates (five studies, n = 15 781; RR = 1.48, 95% CI = 1.31-1.67; I2 = 0%), but post-warming survival rates were not affected (three studies, n = 12 452; RR = 0.99, 95% CI = 0.97-1.01; I2 = 71%) by 'single biopsy + double vitrification'.

LIMITATIONS, REASONS FOR CAUTION

All studies included in this meta-analysis were retrospective with varying levels of heterogeneity for different outcomes. Not all studies had accounted for potential confounding factors. Only one study reported neonatal outcomes.

WIDER IMPLICATIONS OF THE FINDINGS

Our data indicated adverse impacts of 'double biopsy + double vitrification' and 'single biopsy + double vitrification' on clinical outcomes following euploid blastocyst transfers. Patients should be carefully consulted about the risks when offered such approaches. The biopsy process should be carried out as carefully and competently as possible to minimize an inconclusive diagnosis.

STUDY FUNDING/COMPETING INTEREST(S)

R.W. is supported by a National Health and Medical Research Council Emerging Leadership Investigator Grant (2009767). There is no other external funding to report. All authors report no conflict of interest.

REGISTRATION NUMBER

CRD42023469143.

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.

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.

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.

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.

Development of an artificial intelligence based model for predicting the euploidy of blastocysts in PGT-A treatments

The euploidy of embryos is unpredictable before transfer in in vitro fertilisation (IVF) treatments without pre-implantation genetic testing (PGT). Previous studies have suggested that morphokinetic characteristics using an artificial intelligence (AI)-based model in the time-lapse monitoring (TLM) system were correlated with the outcomes of frozen embryo transfer (FET), but the predictive effectiveness of the model for euploidy remains to be perfected. In this study, we combined morphokinetic characteristics, morphological characteristics of blastocysts, and clinical parameters of patients to build a model to predict the euploidy of blastocysts and live births in PGT for aneuploidy treatments. The model was effective in predicting euploidy (AUC = 0.879) but was ineffective in predicting live birth after FET. These results provide a potential method for the selection of embryos for IVF treatments with non-PGT.

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.

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.

Accumulation of Cleavage-Stage Embryos by Vitrification may Compromise Embryonic Developmental Potential in Preimplantation Genetic Testing

It was suggested that the embryo pooling was an alternative for patients with insufficient number of embryos for preimplantation genetic testing (PGT) in a single ovarian stimulation cycle. However, limited study noticed whether it is an efficient strategy to pool cleavage-stage embryos by vitrification. This study included 71 cycles with vitrified-warmed and fresh embryos simultaneously for PGT between May 2016 and May 2021. The embryos from the same patients were split into two groups based on the origin: warming group and fresh group. Embryo development, sequencing results, clinical and neonatal outcomes were compared. The results showed that the rate of high-quality embryos in the warming group was significantly higher than that in the fresh group (64.53% versus 52.61%, P = 0.011); however, the available blastocyst rate in this group was significantly lower than that in the fresh group (47.29% versus 57.83%, P = 0.026). There were 96 and 144 blastocysts that underwent trophectoderm (TE) biopsy in warming and fresh groups, respectively. The high-quality blastocyst rate was significantly lower in the warming group compared to the fresh group (57.29% versus 70.14%, P = 0.041). The rates of genetic transferable blastocyst were comparable between the two groups (P = 0.956). There were no statistical differences in terms of embryo implantation, clinical pregnancy, miscarriage rates, and neonatal outcomes between the two groups. In conclusion, this study demonstrated that the cleavage-stage embryo pooling strategy might be unfavorable for the maintenance of embryonic development potential. If not necessary, it is not recommended to pool cleavage-stage embryos for PGT.

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.

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.

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

PURPOSE

To describe diagnostic results following re-biopsy of blastocysts with inconclusive results on preimplantation genetic screening for aneuploidy (PGT-A) and to evaluate the reproductive potential of re-biopsied blastocysts.

METHODS

This retrospective cohort study included all trophectoderm biopsies submitted for PGT-A by a large in vitro fertilization center to a single genetics laboratory from June 2016 to October 2018. PGT-A was performed using next-generation sequencing (NGS). No-result blastocysts that underwent re-biopsy were subsequently classified as euploid, aneuploid, mosaic/segmental, or no-result. Ongoing pregnancy and clinical loss rates were assessed following transfer of re-biopsied blastocysts. Logistic regressions were conducted to account for age and blastocyst morphology.

RESULTS

Of the trophectoderm biopsies submitted for PGT-A, 635/25,199 (2.5%) were categorized as no-result. Those that underwent re-biopsy (n = 250) had a 95.2% diagnostic rate with 140 (56.0%) receiving euploid diagnoses. Thirty-six re-biopsied blastocysts deemed euploid were subsequently transferred, resulting in 18 (50.0%) ongoing pregnancies and 5 (13.9%) clinical losses. After adjusting for age and blastocyst morphology, there remained a lower ongoing pregnancy rate and a trend towards higher clinical loss rate following transfer of a re-biopsied blastocyst. When compared to blastocysts that underwent the same number of vitrification-warming cycles but only one biopsy, there were no differences in outcomes.

CONCLUSIONS

Failure to obtain an analytical result does not change the probability that a given blastocyst is euploid. Pregnancy outcomes following transfer of re-biopsied blastocysts are favorable, but further data must be accrued for an adequately powered comparison with outcomes after transfer of blastocysts biopsied once.

Inconclusive results in preimplantation genetic testing: go for a second biopsy?

The transition in biopsy timing from blastomere to trophectoderm biopsy has led to a remarkable decrease in the percentage of undiagnosed blastocysts. However, patients with few or no euploid blastocysts can be affected by this residual percentage of diagnosis failure. The aim of this study is to assess whether blastocyst rebiopsy and revitrification is an efficient and safe procedure to be applied in cases of no results after analysis. Fifty-three patients agreed to the warming of 61 blastocysts to perform a second biopsy and PGT-A by aCGH. Only 75.4% of the blastocysts survived, reexpanded, and could be rebiopsied. After the second biopsy and analysis, 95.6% of the blastocysts were successfully diagnosed with an euploidy rate of 65.9%. Eighteen euploid blastocysts were warmed and transferred to 18 patients with a 100% survival and reexpansion rate. Seven clinical pregnancies have been achieved with 4 live births, 1 ongoing pregnancy, and 2 miscarriages. Thus, although few transfers of rebiopsied and revitrified blastocysts have been performed till date, our preliminary results show that this approach is efficient and safe to be applied for undiagnosed blastocysts, as it ultimately allows the transfer of euploid blastocysts and good clinical outcomes.

The effect of repeated biopsy on pre-implantation genetic testing for monogenic diseases (PGT-M) treatment outcome

PURPOSE

To study the outcome of repeated biopsy for pre-implantation genetic testing in case of failed genetic diagnosis in the first biopsy.

METHODS

The study group included 81 cycles where embryos underwent re-biopsy because there were no transferable embryos after the first biopsy: in 55 cycles, the first procedure was polar body biopsy (PBs) and the second cleavage-stage (BB); in 26 cycles, the first was BB and the second trophectoderm (BLAST) biopsy. The control group included 77 cycles where embryos underwent successful genetic diagnosis following the first biopsy, matched by maternal age, egg number, genetic inheritance type, and embryonic stage at the first biopsy. We measured genetic diagnosis rate, clinical pregnancy rates (PRs), live-birth rates (LBRs), gestational age, and birth weight.

RESULTS

For repeated biopsy, genetic diagnosis was received in 67/81 cycles (82.7%); at a higher rate in PB + BB than in BB + BLAST (49/55, 89.1% and 18/26, 69.2% respectively, p = 0.055). Transferable embryos were found in 47 and 68 cycles in the study and the control groups. PRs/ET were 20/47 (42.6%) and 36/68 (52.9%) (p = 0.27), 16/36 (44.4%) following PB + BB, and 4/11 (36.4%) following BB + BLAST (p = 0.74). LBRs/ET were 13/47 (27.7%) in study group, and 28/68 (41.2%) in the controls (p = 0.14), 10/36 (27.8%) following PB + BB group, and 3/11 (27.3%) following BB + BLAST (p > 0.99). Gestational age and birth weight were similar in all groups.

CONCLUSIONS

Re-biopsy of embryos when no genetic diagnosis could be reached following the first biopsy, achieved high rates of genetic diagnosis, pregnancies, and live births.

Aportes éticos y jurídicos para la discusión sobre el Diagnóstico Genético Preimplantacional: una aproximación desde el concebido

El diagnostico genético preimplantacional introduce importantes preguntas éticas y jurídicas; entonces, .cuales son los criterios que se deben tener en cuenta? En esta investigación se describen los límites que han considerado algunas legislaciones a la hora de regular esta técnica. Adicionalmente, se analizan fallos que se han pronunciado sobre problemas jurídicos causados por su aplicación, entre ellos, el error en el diagnóstico.

Polar body transfer restores the developmental potential of oocytes to blastocyst stage in a case of repeated embryo fragmentation

PURPOSE

We aimed to determine the developmental potential of human reconstructed oocytes after polar body genome transfer (PBT) and to report the case of a woman with multiple cycles of severe embryo fragmentation.

METHODS

Fresh and cryopreserved first polar bodies (PB1s) were transferred to enucleated metaphase II oocytes (PB1T), while fresh PB2s were removed from fertilized oocytes and used instead of the female pronucleus in donor zygotes. Reconstructed oocytes underwent intracytoplasmic sperm injection (ICSI) and were cultured to blastocyst. Biopsied trophectoderm cells of PBT-derived blastocysts were screened for chromosomes by next-generation sequencing (NGS). Then, cryopreserved PB1T was carried out in one woman with a history of several cycles of extensive embryo fragmentation, and the blastocysts derived from PB1T were screened for aneuploidy but not transferred to the patient.

RESULTS

There were no significant differences in the rates of normal fertilization and blastocyst formation between fresh and cryopreserved PB1T and control oocytes. Of the three fresh and three cryopreserved PB1T-derived blastocysts, two and one blastocysts exhibited normal diploidy respectively. In contrast, 17 PB2 transfers yielded 16 two pronuclei (2PN) zygotes with one normal and one small-sized pronucleus each and no blastocyst formation. In the female patient, 18 oocytes were inseminated by ICSI in the fourth cycle and the PB1s were biopsied. Although the embryos developed from the patient's own oocytes showed severe fragmentation, the oocytes reconstructed after PB1T produced three chromosomally normal blastocysts.

CONCLUSIONS

Normal blastocysts can develop from human reconstructed oocytes after PB1T. The application of the first PB transfers may be beneficial to patients with a history of poor embryo development and excessive fragmentation.

Developmental potential of clinically discarded human embryos and associated chromosomal analysis

Clinically discarded human embryos, which are generated from both normal and abnormal fertilizations, have the potential of developing into blastocysts. A total of 1,649 discarded human embryos, including zygotes containing normal (2PN) and abnormal (0PN, 1PN, 3PN and ≥4PN) pronuclei and prematurely cleaved embryos (2Cell), were collected for in vitro culture to investigate their developmental potential and chromosomal constitution using an SNP array-based chromosomal analysis. We found that blastocyst formation rates were 63.8% (for 2Cell embryos), 22.6% (2PN), 16.7% (0PN), 11.2% (3PN) and 3.6% (1PN). SNP array-based chromosomal analysis of the resultant blastocysts revealed that the percentages of normal chromosomes were 55.2% (2Cell), 60.7% (2PN), 44.4% (0PN) and 47.4% (0PN). Compared with clinical preimplantation genetic diagnosis (PGD) data generated with clinically acceptable embryos, results of the SNP array-based chromosome analysis on blastocysts from clinically discarded embryos showed similar values for the frequency of abnormal chromosome occurrence, aberrant signal classification and chromosomal distribution. The present study is perhaps the first systematic analysis of the developmental potential of clinically discarded embryos and provides a basis for future studies.

Number of biopsied trophectoderm cells is likely to affect the implantation potential of blastocysts with poor trophectoderm quality

OBJECTIVE

To evaluate whether the developmental potential of the blastocyst is affected by the number of trophectoderm (TE) cells biopsied in preimplantation genetic diagnosis (PGD) cycles.

DESIGN

Retrospective study.

SETTING

University-affiliated center.

PATIENT(S)

Women underwent PGD cycles of blastocyst biopsy and fluorescence in situ hybridization analysis.

INTERVENTION(S)

Not applicable.

MAIN OUTCOME MEASURE(S)

Biopsied TE cell number of blastocysts, survival, and implantation rates.

RESULT(S)

The biopsied TE cell number was affected by the TE quality and experience of different embryologists. The diagnostic efficiency increased when from one to five cells were biopsied (86.7%, 91.7%%, 96.0%, 96.8%, to 98.7%) and was maximized when more than six cells were biopsied. To compare the clinical efficiencies, blastocysts were divided into four groups according to biopsied TE cell number: 1-5, 6-10, 11-15, and 16-41. For the blastocysts with grade A TE score, no significant difference was observed in the survival and implantation rates among the four groups. For the blastocysts with grades B and C TE scores, the survival rates showed no significant differences among the four groups, but a significant decreasing trend in implantation rates was observed with increasing biopsied TE cell number.

CONCLUSION(S)

The implantation potential is negatively affected by the biopsied TE cell number in blastocysts with poor TE morphological score.