Preimplantation genetic testing for aneuploidy in poor ovarian responders with four or fewer oocytes retrieved

Preimplantation genetic testing for aneuploidy optimizes reproductive outcomes in recurrent reproductive failure: a systematic review

Introduction

Recurrent reproductive failure (RRF) is a common pregnancy complication, imposing great physical, emotional and financial burden for the suffered couples. The leading cause of RRF is believed to be aneuploid embryo, which could be solved by preimplantation genetic testing for aneuploidy (PGT-A) in theory. With molecular genetic development, PGT-A based on comprehensive chromosomal screening (CCS) procedures and blastocyst biopsy is widely applied in clinical practice. However, its effects in RRF were not defined yet.

Methods

A systematic bibliographical search was conducted without temporal limits up to June, 2023. Studies about the effects of PGT-A based on CCS procedures and blastocyst biopsy in RRF were included.

Results

Twenty studies about the effects of PGT-A based on CCS procedures and blastocyst biopsy in RRF were included. It revealed that PGT-A could optimise the reproductive outcomes of RRF sufferers, especially in those with advanced age. However, in patients with multiple occurrences of pregnancy losses, the benefits of PGT-A were limited.

Discussion

More randomized controlled trials with large sample size are required to evaluate the benefits of PGT-A in RRF sufferers and identify which population would benefit the most.

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'.

The developmental competence of human metaphase I oocytes with delayed maturation in vitro

OBJECTIVE

To evaluate whether metaphase I (MI) oocytes completing maturation in vitro to metaphase II ("MI-MII oocytes") have similar developmental competence as the sibling metaphase II (MII) oocytes that reached maturity in vivo.

DESIGN

Retrospective cohort study.

SETTING

Academic medical center.

PATIENT(S)

A total of 1,124 intracytoplasmic sperm injection (ICSI) cycles from 800 patients at a single academic center between April 2016 and December 2020 with at least 1 MII oocyte immediately after retrieval and at least 1 sibling "MI-MII oocyte" that was retrieved as MI and matured to MII in culture before ICSI were included in the study.

INTERVENTION(S)

None.

MAIN OUTCOME MEASURE(S)

A total of 7,865 MII and 2,369 sibling MI-MII oocytes retrieved from the same individuals were compared for the fertilization and blastocyst formation rates. For patients who underwent single euploid blastocyst transfers (n = 406), the clinical pregnancy, spontaneous pregnancy loss, and live birth rates were compared between the 2 groups.

RESULT(S)

The fertilization rate was significantly higher in MII oocytes than in delayed matured MI-MII oocytes (75.9% vs. 56.1%). Similarly, the blastocyst formation rate was higher in embryos derived from MII oocytes than in those from MI-MII oocytes (53.8% vs. 23.9%). The percentage of euploid embryos derived from MII oocytes was significantly higher than that of those from MI-MII oocytes (49.2% vs. 34.7%). Paired comparison of sibling oocytes within the same cycle showed higher developmental competence of the MII oocytes than that of MI-MII oocytes. However, the pregnancy, spontaneous pregnancy loss, and live birth rates after a single euploid blastocyst transfer showed no statistically significant difference between the 2 groups (MII vs. MI-MII group, 65.7% vs. 74.1%, 6.4% vs. 5.0%, and 61.5% vs. 70.0%, respectively).

CONCLUSION(S)

Compared with oocytes that matured in vivo and were retrieved as MII, the oocytes that were retrieved as MI and matured to MII in vitro before ICSI showed lower developmental competence, including lower fertilization, blastocyst formation, and euploidy rates. However, euploid blastocysts from either cohort resulted in similar live birth rates, indicating that the MI oocytes with delayed maturation can still be useful even though the overall developmental competence was lower than that of their in vivo matured counterparts.

What to do with one good quality blastocyst and where do we place the emphasis?

The use of preimplantation genetic testing for aneuploidy (PGT-A) in poor responders undergoing assisted reproductive technology has been a topic of debate with controversial results. It is critical to note the denominators used in data presented. Herein, we comment on the results found in the study by Kahraman et al. on the utility of PGT-A in poor responders with a single, good-quality blastocyst.

Impact of recurrent pregnancy loss history on reproductive outcomes in women undergoing fertility treatment

BACKGROUND

Recurrent pregnancy loss negatively affects the reproductive outcomes of natural conception. Preimplantation genetic testing for aneuploidies has been the focus of interventions in women with recurrent pregnancy loss. However, the risk of no embryos being available, high costs, and uncertainties surrounding its effectiveness limit its use. Factors beyond euploidy, such as an appropriate intrauterine environment, are also important for improving the reproductive outcomes in women with recurrent pregnancy loss. It remains unknown whether a history of recurrent pregnancy loss can affect reproductive outcomes after fertility treatment.

OBJECTIVE

This study aimed to investigate the impact of history of recurrent pregnancy loss on the reproductive outcomes of women undergoing fertility treatment.

STUDY DESIGN

This was a retrospective cohort study of women who underwent their first frozen embryo transfer cycle or intrauterine insemination cycle between January 2014 and July 2020 in Shanghai, China. We excluded couples with known karyotypic abnormalities (eg, balanced translocation) or uterine malformation. We performed multivariate binary logistic regressions for biochemical pregnancy, miscarriage, and live birth rates to investigate the associations between recurrent pregnancy loss history and reproductive outcomes.

RESULTS

A total of 29,825 women who underwent frozen embryo transfer cycles and 5476 women who underwent intrauterine insemination cycles were included in this study. In those who underwent frozen embryo transfer, history of recurrent pregnancy loss was not significantly associated with biochemical pregnancy (adjusted odds ratio, 1.19; 95% confidence interval, 0.87-1.63), miscarriage (adjusted odds ratio, 0.99; 95% confidence interval, 0.78-1.26), or live birth rates (adjusted odds ratio, 0.91; 95% confidence interval, 0.79-1.06). Similarly, in frozen embryo transfer cycles that led to clinical pregnancy, recurrent pregnancy loss history was not significantly associated with live birth (adjusted odds ratio, 0.99; 95% confidence interval, 0.76-1.28) or miscarriage rates (adjusted odds ratio, 1.04; 95% confidence interval, 0.81-1.35). In women with intrauterine insemination, history of recurrent pregnancy loss showed no significant associations with fertility outcomes in all cycles ([adjusted odds ratio, 1.36; 95% confidence interval, 0.88-2.10] for live birth rate and [adjusted odds ratio, 1.74; 95% confidence interval, 0.75-4.01], for miscarriage rate) and in cycles that led to clinical pregnancy ([adjusted odds ratio, 0.70; 95% confidence interval, 0.31-1.63] for live birth rate and [adjusted odds ratio, 1.45; 95% confidence interval, 0.58-3.63] for miscarriage rate).

CONCLUSION

In women without obvious chromosome abnormality and uterine malformation who undergo fertility treatment, recurrent pregnancy loss history was not significantly associated with miscarriage and live birth rates, suggesting that it has little or no prognostic value in predicting the reproductive outcomes of frozen embryo transfer or intrauterine insemination cycles.

What to advise to patients with only one good quality blastocyst, PGT-A or not? Outcomes of 2064 cycles

PURPOSE

To evaluate whether preimplantation genetic testing for aneuploidy (PGT-A) is beneficial for patients who have only one blastocyst available for biopsy or transfer.

METHODS

This retrospective study was based on 1126 single blastocyst PGT-A and 938 non-PGT-A cycles, a total of 2064 ART cycles which resulted in a single good quality blastocyst in women between 20 and 45 years old. The PGT-A group had 225 single euploid embryo transfer cycles and the non-PGT-A group had 938 single blastocyst embryo transfer cycles.

RESULTS

In the generalized linear mixed model (GLMM), female age and PGT-A variables were found to be significant variables on pregnancy outcomes. In the PGT-A cases, regardless of the effect of other variables, the probabilities of clinical pregnancy and live birth were found to be 3.907 and 3.448 fold higher respectively than in the non-PGT-A cases (p < 0.001). In non PGT-A cases, the probability of a total pregnancy loss was found to be 1.943 fold higher (p = 0.013).

CONCLUSION

PGT-A in the presence of a single blastocyst significantly increases clinical pregnancy and live birth rates and decreases total pregnancy losses regardless of age. In addition, aneuploid embryo transfer cancelations prevent ineffective and potentially risky transfers.

Evaluating the application value of NGS-based PGT-A by screening cryopreserved MDA products of embryos from PGT-M cycles with known transfer outcomes

PURPOSE

To determine the application value of next-generation sequencing (NGS)-based preimplantation genetic testing for aneuploidies (PGT-A).

METHODS

We conducted a retrospective case-control study on a cohort of frozen-thawed embryo transfer (FET) cycles following preimplantation genetic testing for monogenic disorders (PGT-M) between 2014 and 2017. Cycles that produced live births or early miscarriages were divided into live birth group (n = 76) or miscarriage group (n = 19), respectively. The NGS-based aneuploidy screening was performed on the multiple displacement amplification (MDA) products of the embryonic trophectoderm biopsy samples that were cryopreserved following PGT-M.

RESULTS

In the live birth group, 75% (57/76) embryos were euploid and 14.5% (11/76) were aneuploid. The remaining 10.5% (8/76) embryos were NGS-classified mosaic with the high- (≥ 50%) and low-level (< 50%) mosaicism rates at 7.9% (6/76) and 2.6% (2/76), respectively. In the miscarriage group, only 23.5% (4/17) embryos were aneuploid, while 58.8% (10/17) were euploid and 17.6% (3/17) were NGS-classified mosaic with the high- and low-level mosaicism rates at 11.8% (2/17) and 5.9% (1/17), respectively. For live birth and miscarriage groups, the transferable rate was 82.9% (63/76) and 70.6% (12/17), respectively, whereas the untransferable rate was 17.1% (13/76) and 29.4% (5/17), respectively.

CONCLUSION

The application of NGS-based PGT-A remains questionable, as it may cause at least one in six embryos with reproductive potential to be discarded and prevent miscarriage in less than one in three embryos in single-gene disease carriers.

Embryo attrition in planned PGT-A: predicting the number of available blastocysts for transfer

PURPOSE

During a typical IVF cycle, there is unavoidable attrition from oocytes retrieved to blastocysts formed. Some patients will not have blastocysts available to biopsy or embryos for transfer. The purpose of this study was to predict the number of transferable blastocysts available for patients based on their age and number of 2pn zygotes.

METHODS

This was a retrospective cohort study of all fresh autologous IVF and ICSI cycles in which PGT-A was planned from 1/2012 to 3/2020. In total, 746 cycles from 571 patients were analyzed. Patient cycles were stratified into two groups: less than four 2pn zygotes (n = 85) and at least four 2pn zygotes (n = 661). Cycles were then stratified by patient age. Cycle outcomes, including number of cleavage-stage embryos, blastocysts, euploid blastocysts, and low level mosaic blastocysts, were determined.

RESULTS

Cleavage-rate was independent of age and number of 2pn zygotes and ranged between 96 and 100%. Blastocyst conversion and euploid blastocyst conversion rates were directly correlated to age, ranging from 52 to 83% for blastocyst conversion and 0-28% for euploid blastocyst conversion. For patients above the age of 40 years with less than four 2pn zygotes, the risk of having no transferable embryos was 99.7%.

CONCLUSION

While the literature demonstrates higher live birth rates with the use of PGT-A in women of advancing age, this is inconsequential if there is no embryo available to transfer. Women over 40 years with less than four 2pn zygotes should consider transfer of one or more untested embryos either on day 3 or on day 5.

Genetic Testing for Aneuploidy in Patients Who Have Had Multiple Miscarriages: A Review of Current Literature

Recurrent pregnancy loss (RPL) is an obstetrical complication that affects about 3% of reproductive age couples. Genetic and non-genetic causes of RPL are multiple; however, aneuploidy is the most common obstetrical complication that can explain single and recurrent pregnancy loss (present in about 60% of recognized clinical pregnancies which result in a miscarriage). Parental karyotyping will only be of potential benefit for 2 to 5 percentage of RPL couples who are translocation carriers. Products of conception (POC) karyotype analysis has been used to direct management in RPL and has been shown to be cost-effective, but the technique has many limitations including high culture failure rate and maternal cell contamination. These limitations can be significantly reduced using POC chromosomal microarray (CMA) technology. We believe that POC genetic testing should be performed after the second and subsequent pregnancy loss using CMA. Although the results will not generally alter the course of treatment, the knowledge of the reason for the loss is of great emotional comfort to many patients. In addition, POC CMA performed in conjunction with a regular complete maternal RPL work-up will identify the group of truly unexplained RPL. Thus, only 10% of patients with RPL will complete an evaluation having a euploid loss and an otherwise normal work-up. This group of "truly unexplained RPL" would be ideal for new research trials and therapies. Pre-implantation genetic testing (PGT) technology has improved recently with day 5 trophectoderm biopsy as compared to biopsy on day 3 as well as with the addition of CMA and next-generation sequencing technologies. The most recent studies on PGT-SR (PGT-Structural rearrangement) show improved clinical and live birth rates per pregnancy, as well as decreased miscarriage rate for translocation carriers. PGT-A (PGT-aneuploidy) may have a limited role in RPL in cases with documented recurrent POC aneuploidy.

Genetic testing of products of conception in recurrent pregnancy loss evaluation

Genetic testing of products of conception (POC) has been proposed as a tool to be used in the evaluation of patients with recurrent pregnancy loss (RPL). Following a complete RPL evaluation, POC results may reveal an aneuploidy and provide an explanation for the miscarriage in more than 55% of cases. When the cytogenetic result of the pregnancy loss reveals a euploid pregnancy, management should be directed towards the identification of treatable abnormalities. Furthermore, the results of POC testing might better define a subgroup of patients with unexplained RPL who may benefit from expectant management versus preimplantation genetics (aneuploid unexplained RPL) or investigational therapy (euploid unexplained RPL).

Noninvasive preimplantation genetic testing for aneuploidy exhibits high rates of deoxyribonucleic acid amplification failure and poor correlation with results obtained using trophectoderm biopsy

OBJECTIVE

To validate a commercially available noninvasive preimplantation genetic testing for aneuploidy (niPGT-A) assay by investigating the following: prevalence of deoxyribonucleic acid (DNA) amplification failure with niPGT-A; factors affecting amplification failure with niPGT-A; and frequency of discordant results between niPGT-A and traditional preimplantation genetic testing for aneuploidy.

DESIGN

Prospective cohort study SETTING: Academic-affiliated private practice PATIENT(S): One hundred sixty-six blastocysts and their surrounding culture media from couples undergoing in vitro fertilization between July 2019 and May 2020 were analyzed.

INTERVENTION(S)

Blastocyst-stage spent culture media samples underwent niPGT-A using a commercially available kit that used whole-genome amplification with a modified multiple annealing and looping-based amplification cycle protocol followed by next-generation sequencing. Preimplantation genetic testing for aneuploidy of trophectoderm (TE) biopsies was performed using targeted next-generation sequencing.

MAIN OUTCOME MEASURE(S)

The primary outcome was failure to achieve an interpretable result with niPGT-A. Factors affecting DNA amplification were also assessed. Discrepancies between niPGT-A and TE biopsy results were analyzed, and clinical outcomes were evaluated.

RESULT(S)

Deoxyribonucleic acid amplification failures with niPGT-A were observed in 37.3% (62/166) of the samples. With TE biopsy, no embryos exhibited DNA amplification failure. Embryos with a shorter duration of exposure to the culture media and no evidence of whole-chromosome aneuploidy on the TE biopsy displayed high rates of DNA amplification failure with niPGT-A. Of 104 embryos with both niPGT-A and TE biopsy results available, whole-chromosome discordance was noted in 42 cases (40.4%). Three embryos classified as aneuploid based on the niPGT-A result progressed to successful delivery.

CONCLUSION(S)

The rates of DNA amplification failure were high among the niPGT-A samples, virtually precluding the clinical applicability of niPGT-A in its current form.

The Conundrum of Poor Ovarian Response: From Diagnosis to Treatment

Despite recent striking advances in assisted reproductive technology (ART), poor ovarian response (POR) diagnosis and treatment is still considered challenging. Poor responders constitute a heterogeneous cohort with the common denominator of under-responding to controlled ovarian stimulation. Inevitably, respective success rates are significantly compromised. As POR pathophysiology entails the elusive factor of compromised ovarian function, both diagnosis and management fuel an ongoing heated debate depicted in the literature. From the criteria employed for diagnosis to the plethora of strategies and adjuvant therapies proposed, the conundrum of POR still puzzles the practitioner. What is more, novel treatment approaches from stem cell therapy and platelet-rich plasma intra-ovarian infusion to mitochondrial replacement therapy have emerged, albeit not claiming clinical routine status yet. The complex and time sensitive nature of this subgroup of infertile patients indicates the demand for a consensus on a horizontally accepted definition, diagnosis and subsequent effective treating strategy. This critical review analyzes the standing criteria employed in order to diagnose and aptly categorize POR patients, while it proceeds to critically evaluate current and novel strategies regarding their management. Discrepancies in diagnosis and respective implications are discussed, while the existing diversity in management options highlights the need for individualized management.