Morphokinetics of human blastocyst expansion in vitro

Reproductive aging, preimplantation genetic testing for aneuploidy, and the diameter of blastocysts: does size matter?

There is no doubt that maternal aging, also known as reproductive aging, can contribute to the increased rates of aneuploidy observed in blastocysts generated from women of advanced age who undergo in vitro fertilization (IVF). Additionally, the hatching process of the blastocyst, which is crucial for successful implantation, may be impaired in aneuploid embryos. Aneuploid embryos often exhibit abnormal cell division and chromosomal distribution, which can lead to disruptions in the hatching process. Due to ethical restrictions, preimplantation genetic testing for aneuploidy (PGT-A) is unavailable in all countries. Therefore, our retrospective study of 502 couples who underwent intracytoplasmic sperm injection (ICSI) aimed to elucidate if embryonic features, such as the ability to hatch and embryonic diameter, could be a reliable estimator for the success rate after embryo transfer, especially for women aged 26-45 years, and for IVF clinics which do not have access to PGT-A. The small hatching blastocysts (Bl. 5) group had a significant (p < 0.001) higher percentage of euploid embryos (≤35 Y- 73%, >35Y- 51%) compared to large (Bl. 4) counterparts (≤35 Y-58%, >35 Y- 38%). In patients aged 34-38 years, we detected 10% more euploid blastocysts in the hatching group than the expanding ones, which was a significant difference (p < 0.05). In conclusion, when selecting non-PGT-A tested embryos for embryo transfer (ET) or frozen embryo transfer (FET), a small hatching blastocyst seems to be a better choice than a large expanded one, especially for advanced-age patients for whom the risk of aneuploidy is higher.

Quantitative Standardized Expansion Assay: An Artificial Intelligence-Powered Morphometric Description of Blastocyst Expansion and Zona Thinning Dynamics

Artificial intelligence applied to time-lapse microscopy may revolutionize embryo selection in IVF by automating data collection and standardizing the assessments. In this context, blastocyst expansion dynamics, although being associated with reproductive fitness, have been poorly studied. This retrospective study (N = 2184 blastocysts from 786 cycles) exploited both technologies to picture the association between embryo and inner-cell-mass (ICM) area in µm2, the ICM/Trophectoderm ratio, and the zona pellucida thickness in µm (zp-T) at sequential blastocyst expansion stages, with (i) euploidy and (ii) live-birth per transfer (N = 548 transfers). A quantitative-standardized-expansion-assay (qSEA) was also set-up; a novel approach involving automatic annotations of all expansion metrics every 30 min across 5 h following blastulation. Multivariate regressions and ROC curve analyses were conducted. Aneuploid blastocysts were slower, expanded less and showed thicker zp. The qSEA outlined faster and more consistent zp thinning processes among euploid blastocysts, being more or as effective as the embryologists in ranking euploid embryo as top-quality of their cohorts in 69% of the cases. The qSEA also outlined faster and more consistent blastocyst expansion and zp thinning dynamics among euploid implanted versus not implanted blastocysts, disagreeing with embryologists' priority choice in about 50% of the cases. In conclusion, qSEA is a promising objective, quantitative, and user-friendly strategy to predict embryo competence that now deserves prospective validations.

Environmental Stress-Induced Alterations in Embryo Developmental Morphokinetics

The association between embryo morphokinetics and its developmental competence is well documented. For instance, early cleaved embryos are more competent in developing to blastocysts, whereas the proportion of abnormally cleaved embryos that further developed to blastocysts is low. Numerous factors, such as the parental age, lifestyle, health, and smoking habits have been reported to affect the embryo morphokinetics and, consequently, its development. However, less is known about the effect of environmental stressors on embryo morphokinetics. The current review discusses the effect of the most concerning environmental stressors on embryo morphokinetics. These stresses include heat stress and human-made chemicals such as phthalates (e.g., bis-(2-ethylhexyl phthalate, dibutyl phthalate, dimethyl phthalate, and their primary metabolites), herbicides (e.g., diaminochlorotriazine, the primary metabolite of atrazine), pharmaceutical compounds (e.g., carbamazepine, nocodazole) and pro-oxidant agents (cumene hydroperoxide, Triton X-100), as well as naturally occurring toxins such as mycotoxin (e.g., aflatoxin B1 and its metabolite, and ochratoxin A). In addition, this review discusses the effect of ionizing or non-ionizing radiation and viral infections (e.g., SARS-CoV-2, papillomavirus). Finally, it points out some potential mechanisms that underlie the impairment of embryo morphokinetics, and it suggests protective compounds, mainly the supplementation of antioxidants to improve the morphokinetics, and consequently, the embryo developmental competence.

Multiple collapses of blastocysts after full blastocyst formation is an independent risk factor for aneuploidy - a study based on AI and manual validation

BACKGROUND

The occurrence of blastocyst collapse may become an indicator of preimplantation embryo quality assessment. It has been reported that collapsing blastocysts can lead to higher rates of aneuploidy and poorer clinical outcomes, but more large-scale studies are needed to explore this relationship. This study explored the characteristics of blastocyst collapse identified and quantified by artificial intelligence and explored the associations between blastocyst collapse and embryo ploidy, morphological quality, and clinical outcomes.

METHODS

This observational study included data from 3288 biopsied blastocysts in 1071 time-lapse preimplantation genetic testing cycles performed between January 2019 and February 2023 at a single academic fertility center. All transferred blastocysts are euploid blastocysts. The artificial intelligence recognized blastocyst collapse in time-lapse microscopy videos and then registered the collapsing times, and the start time, the recovery duration, the shrinkage percentage of each collapse. The effects of blastocyst collapse and embryo ploidy, pregnancy, live birth, miscarriage, and embryo quality were studied using available data from 1196 euploid embryos and 1300 aneuploid embryos.

RESULTS

5.6% of blastocysts collapsed at least once only before the full blastocyst formation (tB), 19.4% collapsed at least once only after tB, and 3.1% collapsed both before and after tB. Multiple collapses of blastocysts after tB (times ≥ 2) are associated with higher aneuploid rates (54.6%, P > 0.05; 70.5%, P < 0.001; 72.5%, P = 0.004; and 71.4%, P = 0.049 in blastocysts collapsed 1, 2, 3 or ≥ 4 times), which remained significant after adjustment for confounders (OR = 2.597, 95% CI 1.464-4.607, P = 0.001). Analysis of the aneuploid embryos showed a higher ratio of collapses and multiple collapses after tB in monosomies and embryos with subchromosomal deletion of segmental nature (P < 0.001). Blastocyst collapse was associated with delayed embryonic development and declined blastocyst quality. There is no significant difference in pregnancy and live birth rates between collapsing and non-collapsing blastocysts.

CONCLUSIONS

Blastocyst collapse is common during blastocyst development. This study underlined that multiple blastocyst collapses after tB may be an independent risk factor for aneuploidy which should be taken into account by clinicians and embryologists when selecting blastocysts for transfer.

How great thou ART: biomechanical properties of oocytes and embryos as indicators of quality in assisted reproductive technologies

Assisted Reproductive Technologies (ART) have revolutionized infertility treatment and animal breeding, but their success largely depends on selecting high-quality oocytes for fertilization and embryos for transfer. During preimplantation development, embryos undergo complex morphogenetic processes, such as compaction and cavitation, driven by cellular forces dependent on cytoskeletal dynamics and cell-cell interactions. These processes are pivotal in dictating an embryo's capacity to implant and progress to full-term development. Hence, a comprehensive grasp of the biomechanical attributes characterizing healthy oocytes and embryos is essential for selecting those with higher developmental potential. Various noninvasive techniques have emerged as valuable tools for assessing biomechanical properties without disturbing the oocyte or embryo physiological state, including morphokinetics, analysis of cytoplasmic movement velocity, or quantification of cortical tension and elasticity using microaspiration. By shedding light on the cytoskeletal processes involved in chromosome segregation, cytokinesis, cellular trafficking, and cell adhesion, underlying oogenesis, and embryonic development, this review explores the significance of embryo biomechanics in ART and its potential implications for improving clinical IVF outcomes, offering valuable insights and research directions to enhance oocyte and embryo selection procedures.

Using blastocyst re-expansion rate for deciding when to warm a new blastocyst for single vitrified-warmed blastocyst transfer

RESEARCH QUESTION

Can predictive post-warm parameters that support the decision to transfer a warmed blastocyst or to warm another blastocyst be identified in women with multiple frozen-vitrified blastocysts?

DESIGN

Retrospective single-centre observational cohort analysis. A total of 1092 single vitrified-warmed blastocyst transfers (SVBT) with known Gardner score, maternal age and live birth were used to develop live birth prediction models based on logistic regression, including post-warm re-expansion parameters. Time-lapse incubation was used for pre-vitrification and post-warm embryo culture. A dataset of 558 SVBT with the same inclusion criteria was used to validate the model, but with known clinical pregnancy outcome instead of live birth outcome.

RESULTS

Three different logistic regression models were developed for predicting live birth based on post-warm blastocyst re-expansion. Different post-warm assessment times indicated that a 2-h post-warm culture period was optimal for live birth prediction (model 1). Adjusting for pre-vitrification Gardner score (model 2) and in combination with maternal age (model 3) further increased predictability (area under the curve [AUC] = 0.623, 0.633, 0.666, respectively). Model validation gave an AUC of 0.617, 0.609 and 0.624, respectively. The false negative rate and true negative rate for model 3 were 2.0 and 10.1 in the development dataset and 3.5 and 8.0 in the validation dataset.

CONCLUSIONS

Clinical application of a simple model based on 2 h of post-warm re-expansion data, pre-vitrification Gardner score and maternal age can support a standardized approach for deciding if warming another blastocyst may increase the likelihood of live birth in SVBT.

Pre-Vitrification and Post-Warming Variables of Vitrified-Warmed Blastocysts That Are Predictable for Implantation

Human IVF embryos that are not used for fresh transfer are cryopreserved by vitrification for later embryo transfers. This study evaluates pre-vitrification and post-warming embryo characteristics that are suitable to predict the chance of clinical pregnancy in single vitrified blastocyst transfer (SVBT) cycles. In a multicenter observational trial (IMBOS trial), embryos were cultured in a time-lapse system before and after vitrification. Associations between clinical pregnancy, morphokinetic parameters, blastocyst collapse, KIDScore D5, pre-vitrification and post-warming Gardner scores, post-warming blastocyst size and re-expansion rates before SVBT were analyzed in 182 SVBTs which resulted in 89 clinical pregnancies. No association was found between clinical pregnancy after SVBT and the number of collapses or the maximal collapse size before vitrification. The multifactorial analysis of pre-vitrification Gardner scores showed a significant association with clinical pregnancy for trophectoderm grading but not for expansion/hatching status and inner cell mass grading. A significant association with clinical pregnancy was found for the time to reach a blastocyst after pronuclear fading (tB-tPNf), KIDScore D5 and post-warming size but not the rate of expansion or maximal expansion size. The selection of blastocysts for SVBT could benefit from using pre-vitrification parameters like tB-tPNf, trophectoderm grading and post-warming blastocyst size.

Comparison of euploid blastocyst expansion with subgroups of single chromosome, multiple chromosome, and segmental aneuploids using an AI platform from donor egg embryos

PURPOSE

This retrospective observational study compares how different classes of blastocyst genotypes from egg donor cycles differentially blastulate and expand using a standard assay.

METHODS

Quantitative measurements of expansion utilized a customized neural network that segments all sequential time-lapse images during the first 10 h of expansion.

RESULTS

Analyses were performed using two developmental time perspectives using time-lapse imaging. The first was the time to blastocyst formation (tB), which broadly reflects variations in developmental rate. Euploidy peaked at 100-115 h from fertilization. In contrast, aneuploidy peaks flanked this interval bi-modally. These distributions limit ploidy discrimination based upon traditional standard grading features when assessed in real time. In contrast, from the second perspective of progressive blastocyst expansion that is normalized to each individual blastocyst's tB time, euploidy was significantly increased at expansion values > 20,000µ2 across all tB intervals studied. A Cartesian coordinate plot graphically summarizes information useful to rank order blastocysts within cohorts for transfer. Defined aneuploidy subgroups, distinguished by the number and complexity of chromosomes involved, also showed distributive differences from both euploids and from each other. A small subset of clinically significant trisomies did not show discriminating features separating them from other euploids.

CONCLUSION

A standard assay of blastocyst expansion normalized to each individual blastocyst's time of blastocyst formation more usefully discriminates euploidy from aneuploidy than real-time expansion comparisons using absolute developmental time from fertilization.

Human blastocyst spontaneous collapse is associated with worse morphological quality and higher degeneration and aneuploidy rates: a comprehensive analysis standardized through artificial intelligence

STUDY QUESTION

What are the factors associated with human blastocyst spontaneous collapse and the consequences of this event?

SUMMARY ANSWER

Approximately 50% of blastocysts collapsed, especially when non-viable, morphologically poor and/or aneuploid.

WHAT IS KNOWN ALREADY

Time-lapse microscopy (TLM) is a powerful tool to observe preimplantation development dynamics. Lately, artificial intelligence (AI) has been harnessed to automate and standardize such observations. Here, we adopted AI to comprehensively portray blastocyst spontaneous collapse, namely the phenomenon of reduction in size of the embryo accompanied by efflux of blastocoel fluid and the detachment of the trophectoderm (TE) from the zona pellucida (ZP). Although the underlying causes are unknown, blastocyst spontaneous collapse deserves attention as a possible marker of reduced competence.

STUDY DESIGN, SIZE, DURATION

An observational study was carried out, including 2348 TLM videos recorded during preimplantation genetic testing for aneuploidies (PGT-A, n = 720) cycles performed between January 2013 and December 2020. All embryos in the analysis at least reached the time of starting blastulation (tSB), 1943 of them reached full expansion, and were biopsied and then vitrified.

PARTICIPANTS/MATERIALS, SETTING, METHODS

ICSI, blastocyst culture, TE biopsy without Day 3 ZP drilling, comprehensive chromosome testing and vitrification were performed. The AI software automatically registered tSB and time of expanding blastocyst (tEB), start and end time of each collapse, time between consecutive collapses, embryo proper area, percentage of shrinkage, embryo:ZP ratio at embryo collapse, time of biopsy (t-biopsy) and related area of the fully (re-)expanded blastocyst before biopsy, time between the last collapse and biopsy. Blastocyst morphological quality was defined according to both Gardner's criteria and an AI-generated implantation score. Euploidy rate per biopsied blastocyst and live birth rate (LBR) per euploid single embryo transfer (SET) were the main outcomes. All significant associations were confirmed through regression analyses. All couple, cycle and embryo main features were also investigated for possible associations with blastocyst spontaneous collapse.

MAIN RESULTS AND THE ROLE OF CHANCE

At least one collapsing embryo (either viable or subsequently undergoing degeneration) was recorded in 559 cycles (77.6%) and in 498 cycles (69.2%) if considering only viable blastocysts. The prevalence of blastocyst spontaneous collapse after the tSB, but before the achievement of full expansion, was 50% (N = 1168/2348), irrespective of cycle and/or couple characteristics. Blastocyst degeneration was 13% among non-collapsing embryos, while it was 18%, 20%, 26% and 39% among embryos collapsing once, twice, three times or ≥4 times, respectively. The results showed that 47.3% (N = 918/1943) of the viable blastocysts experienced at least one spontaneous collapse (ranging from 1 up to 9). Although starting from similar tSB, the number of spontaneous collapses was associated with a delay in both tEB and time of biopsy. Of note, the worse the quality of a blastocyst, the more and the longer its spontaneous collapses. Blastocyst spontaneous collapse was significantly associated with lower euploidy rates (47% in non-collapsing and 38%, 32%, 31% and 20% in blastocysts collapsing once, twice, three times or ≥4 times, respectively; multivariate odds ratio 0.78, 95%CI 0.62-0.98, adjusted P = 0.03). The difference in the LBR after euploid vitrified-warmed SET was not significant (46% and 39% in non-collapsing and collapsing blastocysts, respectively).

LIMITATIONS, REASONS FOR CAUTION

An association between chromosomal mosaicism and blastocyst collapse cannot be reliably assessed on a single TE biopsy. Gestational and perinatal outcomes were not evaluated. Other culture strategies and media should be tested for their association with blastocyst spontaneous collapse. Future studies with a larger sample size are needed to investigate putative impacts on clinical outcomes after euploid transfers.

WIDER IMPLICATIONS OF THE FINDINGS

These results demonstrate the synergistic power of TLM and AI to increase the throughput of embryo preimplantation development observation. They also highlight the transition from compaction to full blastocyst as a delicate morphogenetic process. Blastocyst spontaneous collapse is common and associates with inherently lower competence, but additional data are required to deepen our knowledge on its causes and consequences.

STUDY FUNDING/COMPETING INTEREST(S)

There is no external funding to report. I.E., A.B.-M., I.H.-V. and B.K. are Fairtility employees. I.E. and B.K. also have stock or stock options of Fairtility.

TRIAL REGISTRATION NUMBER

N/A.

Longitudinal surface measurements of human blastocysts show that the dynamics of blastocoel expansion are associated with fertilization method and ongoing pregnancy

BACKGROUND

Despite all research efforts during this era of novel time-lapse morphokinetic parameters, a morphological grading system is still routinely being used for embryo selection at the blastocyst stage. The blastocyst expansion grade, as evaluated during morphological assessment, is associated with clinical pregnancy. However, this assessment is performed without taking the dynamics of blastocoel expansion into account. Here, we studied the dynamics of blastocoel expansion by comparing longitudinal blastocoel surface measurements using time-lapse embryo culture. Our aim was to first assess if this is impacted by fertilization method and second, to study if an association exists between these measurement and ongoing pregnancy.

METHODS

This was a retrospective cohort study including 225 couples undergoing 225 cycles of in vitro fertilization (IVF) treatment with time-lapse embryo culture. The fertilization method was either conventional IVF, intracytoplasmic sperm injection (ICSI) with ejaculated sperm or ICSI with sperm derived from testicular sperm extraction (TESE-ICSI). This resulted in 289 IVF embryos, 218 ICSI embryos and 259 TESE-ICSI embryos that reached at least the full blastocyst stage. Blastocoel surface measurements were performed on time-lapse images every hour, starting from full blastocyst formation (tB). Linear mixed model analysis was performed to study the association between blastocoel expansion, the calculated expansion rate (µm²/hour) and both fertilization method and ongoing pregnancy.

RESULTS

The blastocoel of both ICSI embryos and TESE-ICSI embryos was significantly smaller than the blastocoel of IVF embryos (beta -1121.6 µm²; 95% CI: -1606.1 to -637.1, beta -646.8 µm²; 95% CI: -1118.7 to 174.8, respectively). Still, the blastocoel of transferred embryos resulting in an ongoing pregnancy was significantly larger (beta 795.4 µm²; 95% CI: 15.4 to 1575.4) and expanded significantly faster (beta 100.9 µm²/hour; 95% CI: 5.7 to 196.2) than the blastocoel of transferred embryos that did not, regardless of the fertilization method.

CONCLUSION

Longitudinal blastocyst surface measurements and expansion rates are promising non-invasive quantitative markers that can aid embryo selection for transfer and cryopreservation.

TRIAL REGISTRATION

Our study is a retrospective observational study, therefore trial registration is not applicable.

Focus on time-lapse analysis: blastocyst collapse and morphometric assessment as new features of embryo viability

The main goal of assisted reproductive technology (ART) is to achieve a healthy singleton live birth after the transfer of one embryo. A major objective of IVF scientists has always been to use adequate criteria for selecting the embryo for transfer according to its implantation potential. Indeed, embryo quality is usually assessed by evaluating visual morphology, which relies on the removal of the embryo from the incubator and might include inter- and intra-evaluator variation among embryologists. Recently, an advancement in embryo culture has taken place with the introduction of a new type of incubator with an integrated time-lapse monitoring system, which enables embryologists to analyse the dynamic events of embryo development from fertilization to blastocyst formation. This novel practice is rapidly growing and has been used in many IVF centres worldwide. Therefore, the main aim of this review is to present the benefits of time-lapse monitoring in a modern embryology laboratory; in particular, we discuss blastocyst collapse and morphometric blastocyst assessment, and analyse their association with embryo viability and implantation potential. In addition, we highlight preliminary studies involving artificial intelligence and machine learning models as non-invasive markers of clinical pregnancy.

Pregnancy prediction performance of an annotation-free embryo scoring system on the basis of deep learning after single vitrified-warmed blastocyst transfer: a single-center large cohort retrospective study

OBJECTIVE

To analyze the performance of an annotation-free embryo scoring system on the basis of deep learning for pregnancy prediction after single vitrified blastocyst transfer (SVBT) compared with the performance of other blastocyst grading systems dependent on annotation or morphology scores.

DESIGN

A single-center large cohort retrospective study from an independent validation test.

SETTING

Infertility clinic.

PATIENT(S)

Patients who underwent SVBT cycles (3,018 cycles, mean ± SD patient age 39.3 ± 4.0 years).

INTERVENTION(S)

None.

MAIN OUTCOME MEASURE(S)

The pregnancy prediction performances of each embryo scoring model were compared using the area under curve (AUC) for predicting the fetal heartbeat status for each maternal age group.

RESULT(S)

The AUCs of the <35 years age group (n = 389) for pregnancy prediction were 0.72 for iDAScore, 0.66 for KIDScore, and 0.64 for the Gardner criteria. The AUC of iDAScore was significantly greater than those of the other two models. For the 35-37 years age group (n = 514), the AUCs were 0.68, 0.68, and 0.65 for iDAScore, KIDScore, and the Gardner criteria, respectively, and were not significantly different. The AUCs of the 38-40 years age group (n = 796) were 0.67 for iDAScore, 0.65 for KIDScore, and 0.64 for the Gardner criteria, and there were no significant differences. The AUCs of the 41-42 years age group (n = 636) were 0.66, 0.66, and 0.63 for iDAScore, KIDScore, and the Gardner criteria, respectively, and there were no significant differences among the pregnancy prediction models. For the >42 years age group (n = 389), the AUCs were 0.76 for iDAScore, 0.75 for KIDScore, and 0.75 for the Gardner criteria, and there were no significant differences. Thus, iDAScore AUC was either the highest or equal to the highest AUC for all age groups, although a significant difference was observed only in the youngest age group.

CONCLUSION(S)

Our results showed that objective embryo assessment by a completely automatic and annotation-free model, iDAScore, performed as well as or even better than more traditional embryo assessment or annotation-dependent ranking tools. iDAScore could be an optimal pregnancy prediction model after SVBT, especially in young patients.

Expression and function of interleukin-1β is required for hamster blastocyst hatching: Involvement of hatching-associated cathepsin proteases

In mammals, the phenomenon of blastocyst hatching is an essential prerequisite for successful implantation. Blastocyst hatching is regulated by various molecules. Of them, cytokines, expressed by preimplantation embryos, are thought to be functionally important in blastocyst development and hatching, but their mechanistic roles are not clearly understood. Here, we examined the involvement of two cytokines, namely, interleukin-1β (IL-1β) and its natural antagonist, IL-1ra, in blastocyst hatching in the golden hamster. Blastocysts expressed both cytokines and their receptor, IL-1rt1. Supplementation of IL-1β to cultured eight-cell embryos improved blastocyst hatching (84.1% ± 4.2% vs. 66.6% ± 6.8%; treated vs. control). This improvement was diminished by IL-1ra treatment (23.6% ± 12.9% vs. 76.4% ± 12.9%; treated vs. control). Interestingly, IL-1β-treated embryos showed increased messenger RNA expression of zonalytic proteases, that is, cathepsin-L and -B by 1.9 ± 0.5- and 3.5 ± 0.1-folds, respectively. This was accompanied by their increased enzyme activities; cathepsin-L by 2.8 ± 0.7 fold and -B by 2.3 ± 0.7-fold. Strikingly, proteases and IL-1β were intensely colocalized to trophectodermal projections of hatching blastocysts. This is the first report to show the involvement of embryonic IL-1β in regulating hatching-associated proteases required for blastocyst hatching.

Deep learning neural network analysis of human blastocyst expansion from time-lapse image files

RESEARCH QUESTION

Can artificial intelligence (AI) discriminate a blastocyst's cellular area from unedited time-lapse image files using semantic segmentation and a deep learning optimized U-Net architecture for use in selecting single blastocysts for transfer?

DESIGN

This platform was retrospectively applied to time-lapse files from 101 sequentially transferred single blastocysts that were prospectively selected for transfer by their highest expansion ranking within cohorts using a 10 h expansion assay rather than standard grading.

RESULTS

The AI platform provides expansion curves and raw data files to classify and compare blastocyst phenotypes within both cohorts and populations. Of 35 sequential unbiopsied single blastocyst transfers, 23 (65.7%) resulted in a live birth. Of 66 sequential single euploid blastocyst transfers, also selected for their most robust expansion, 49 (74.2%) resulted in live birth. The AI platform revealed that the averaged expansion rate was significantly (P = 0.007) greater in euploid blastocysts that resulted in live births compared with those resulting in failure to give a live birth. The platform further provides a framework to analyse fragmentation phenotypes that can test new hypotheses for developmental regulation during the preimplantation period.

CONCLUSIONS

AI can be used to quantitatively describe blastocyst expansion from unedited time-lapse image files and can be used to quantitatively rank-order blastocysts for transfer. Early clinical results from such single blastocyst selection suggests that live birth rates without biopsy may be comparable to those found using single euploid blastocysts in younger, good responder patients.

Clinical pregnancy is significantly associated with the blastocyst width and area: a time-lapse study

In order to maintain pregnancy rates following single embryo transfer, optimisation of embryo culture and selection is vital. Time-lapse monitoring (TLM) has the potential to play a crucial role by providing sequential images of embryo development and minimal disturbance. Therefore, in this study morphometric assessment of blastocyst area and maximum width was performed in order to evaluate if these parameters are associated with pregnancy outcomes in IVF/ICSI cycles. This is a retrospective study of 664 patients who had elective single blastocyst transfer (eSBT). The EmbryoScope drawing tools were used to measure specific variables such as the maximum blastocyst width and blastocyst area. Our results show that women who were pregnant had significantly (P < 0.01) larger blastocyst width [median (range) μm] 184 (125-239) versus non-pregnant, 160 (120-230)] and area [median (range) μm²] 26099 (12101-45,280) versus non-pregnant women, 22,251 (10992-37,931)]. A univariate logistic regression performed showed that blastocyst width [(OR = 1.026, 95% CI = (1.019, 1.033)] was significant (P < 0.01) and for every μm increase of blastocyst width, the odds of clinical pregnancy increase by 2.6%. A univariate logistic regression performed showed that blastocyst area [(OR = 1.00008, 95% CI = (1.00006, 1.00011)] was significant with P < 0.01. For every μm² increase of blastocyst area, our data showed the odds of clinical pregnancy increase by 0.008%. Hosmer-Lemeshow tests of calibrations were performed to verify calibration. Although our findings show a clear correlation between blastocyst dimensions and the clinical pregnancy rate, further studies are necessary to confirm these observations.

Extracellular vesicles, microRNA and the preimplantation embryo: non-invasive clues of embryo well-being

Elective single embryo transfer is rapidly becoming the standard of care in assisted reproductive technology for patients under the age of 35 years with a good prognosis. Clinical pregnancy rates have become increasingly dependent on the selection of a single viable embryo for transfer, and diagnostic techniques facilitating this selection continue to develop. Current progress in elucidating the extracellular vesicle and microRNA components of the embryonic secretome is reviewed, and the potential for these findings to improve clinical embryo selection discussed. Key results have shown that extracellular vesicles and microRNAs are rapidly detectable constituents of the embryonic secretome. Evidence suggests that the vesicular population is largely exosomal in nature, secreted at all stages of preimplantation development and capable of traversing the zona pellucida. Both extracellular vesicle and microRNA concentrations within the secretome are elevated for blastocysts with diminished developmental competence, as indicated either by degeneracy or implantation failure, whereas studies have yet to firmly correlate individual microRNA sequences with pregnancy outcome. These emerging correlations support the viability of extracellular vesicles and microRNAs as the basis for a new diagnostic test to supplement or replace morphokinetic assessment.

Blastocyst collapse as an embryo marker of low implantation potential: a time-lapse multicentre study

Spontaneous blastocyst collapse during in vitro embryo development has been suggested as a novel marker of embryo quality. Therefore, the aim of this multicentre study was to carry out a retrospective multicentre analysis to investigate the correlation between blastocyst collapse and pregnancy outcome. Here, 1297 intracytoplasmic sperm injection (ICSI)/in vitro fertilization (IVF) fresh cycles, with an elective single blastocyst transfer (eSET) were included in this study. Embryos were cultured individually in 6.0% CO2, 5.0% O2, 89.0% N2, using single step medium (GTLTM VitroLife, Sweden) or sequential medium (CookTM, Cook Medical, Australia) and selected for transfer using standard morphological criteria. With the use of time-lapse monitoring (TLM), blastocysts were analyzed by measuring the maximum volume reduction and defined as having collapsed, if there was ≥ 50% volume reduction from the expanded blastocyst and the collapse event. Following embryo replacement, each blastocyst was retrospectively allocated to one of two groups (collapsed or not collapsed). Here, 259 blastocysts collapsed once or more during development (19.9%) and the remaining 1038 either contracted minimally or not collapsed (80.1%). A significantly higher ongoing pregnancy rate (OPR) of 51.9% (95% CI 48.9-59.9%) was observed when blastocysts that had not collapsed were replaced compared with cycles in which collapsed blastocysts were transferred 37.5% (95% CI 31.6-43.4%). This study suggests that human blastocysts that collapse spontaneously during development are less likely to implant and generate a pregnancy compared with embryos that do not. Although this is a retrospective study, the results demonstrated the utility of collapse episodes as new marker of embryo selection following eSET at blastocyst stage.

Failure of complete hatching of ICSI-derived human blastocyst by cell herniation via small slit and insufficient expansion despite ongoing cell proliferation

PURPOSE

To assess the effect of intracytoplasmic sperm injection (ICSI) on embryo hatching and visualise the effects of zona thinning (ZT) on the embryo using time-lapse monitoring.

METHODS

In vitro fertilisation (IVF) (n = 178) and ICSI (n = 110)-derived cryopreserved blastocysts were donated by patients who previously had a baby. This study investigated the impacts of IVF, ICSI, laser-assisted hatching by ZT and formation of ICSI penetration trace on zona pellucida of IVF-derived blastocyst on blastcyst diameter, the estimated number of trophectoderm (TE) cells and completed hatching rate.

RESULTS

The completed hatching rate and diameters of the completely hatched blastocysts at hatching commencement and at the maximum expansion were significantly greater in the IVF than in ICSI groups. The completed hatching rate significantly increased with ZT in both groups. The maximum diameters of the completely hatched blastocysts were significantly smaller in the ZT than in non-ZT groups. The estimated TE cell numbers increased from hatching commencement to their maximum expansion points. The incompletely hatched ICSI-derived blastocysts intermittently herniated cells via small slits until degeneration. The completed hatching rate significantly decreased by the formation of ICSI penetration trace on zona pellucida of IVF-derived blastocyst.

CONCLUSION

ICSI-derived blastocysts intermittently release proliferating cells and extracted TE cells and/or inner cell masses via a small slit; thus, blastocyst expansion is not sufficiently increased, leading to a reduced complete hatching rate. Therefore, the ICSI penetration trace potentially has negative effects on blastocyst expansion process in vitro and is a risk factor for the failure of completed hatching.

Early blastocyst expansion in euploid and aneuploid human embryos: evidence for a non-invasive and quantitative marker for embryo selection

RESEARCH QUESTION

How can the kinetics of human blastocyst expansion be used to evaluate an embryo's ploidy identified using preimplantation genetic testing for aneuploidy (PGT-A)?

DESIGN

This was a retrospective observational study of 188 autologous blastocysts from 34 sequential treatment cycles using PGT-A and blastocyst biopsy. Using time-lapse imaging, blastocyst expansion was evaluated using a quantitative standardized expansion assay (qSEA). Trophectoderm cell division was examined in selected, unbiopsied embryos (n = 7) to evaluate the contribution of mitosis to the expansion rate.

RESULTS

The averaged euploid blastocyst expansion rate was significantly (52.8%) faster than in aneuploid blastocysts (P = 0.0041). Scatterplots, representing 'expansion maps', revealed that both populations showed a similarly overlapping distribution of blastocyst formation times at 80-140 h from fertilization. Euploidy and aneuploidy were better distinguished in regions of higher and lower expansion, respectively, in expansion maps. Based upon the expansion slopes, rank-ordering of individual embryos within cohorts resulted in more than 90% euploid embryos in the first two ranks in patients less than 35 years of age. Additional detailed time-lapse image analysis provided evidence that rapid expansion was associated with robust, integrative cellular mitosis in trophectoderm cells.

CONCLUSIONS

The kinetics of human blastocyst expansion are related to an embryo's ploidy. These preliminary observations describe a new quantitative, non-invasive approach to embryo assessment that may be useful to identify single blastocysts for transfer, particularly in younger patient groups. However, this approach may also be useful for euploid embryo selection after PGT-A. The results support the hypothesis that aneuploidy universally impairs general cellular processes, including cell division, in differentiated cells.

Human frozen-thawed blastocyst morphokinetics observed using time-lapse cinematography reflects the number of trophectoderm cells

Recent studies reported morphokinetic indices for optimal selection of embryos in assisted reproductive technology (ART). The morphokinetics in blastocyst stage include the collapse and re-expansion rates after thawing. However, evaluation methods using these morphokinetics have not been established, mainly because the underlying molecular mechanisms remain unclarified. In this study, we focused on the relationship between these morphokinetic observation of the blastocyst behaviour and the number of cells constituting the blastocyst. We evaluated 38 surplus human frozen-thawed blastocysts using time-lapse cinematography and recorded their expansion, contraction, and hatching. A total of 28 blastocysts expanded in culture (cross-sectional area ≥ 5,000 π μm²). In comparison to the ones that did not, the expanded group presented significantly more number of inner cell mass (ICM) and trophectoderm (TE) cells, which eventually develop into the fetus and placenta, respectively (ICM: Expanded 10.2 ± 6.3 vs. Non-Expanded 6.0 ± 12.3, p < 0.05; TE: Expanded 165.7 ± 74.8 vs. Non-Expanded 57.0 ± 29.4, p < 0.05). Moreover, a positive correlation was found between the expansion rate (up to 4 h) and the number of TE cells (r = 0.558, p = 0.0021). Additionally, blastocysts that hatched had a significantly higher number of TE cells than those that did not (hatching 225.2 ± 61.2 vs. no hatching 121.1 ± 48.6, p < 0.0001). The number of TE cells per unit of cross-sectional area correlated negatively with the contraction time (r = –0.601, p = 0.0007). No correlation between the number of ICM cells and these morphokinetics was detected. In conclusion, our study demonstrates that different morphokinetics of frozen-thawed blastocysts reflect the number of TE cells. The differentiation of blastocysts containing sufficient TE cells would be beneficial for implantation and prognosis of a subsequent pregnancy. Thus, evaluation of these morphokinetics can be an effective method to screen good embryos for ART.

Overall Blastocyst Quality, Trophectoderm Grade, and Inner Cell Mass Grade Predict Pregnancy Outcome in Euploid Blastocyst Transfer Cycles

Background:

Despite recent advances that have improved the pregnancy success rates that can be achieved via in vitro fertilization (IVF) therapy, it is not yet clear which blastocyst morphological parameters best predict the outcomes of single blastocyst transfer. In addition, most of the previous studies did not exclude the effect of embryo aneuploidy on blastocysts transfer. Thus, the present study investigated the predictive value of various parameters on the pregnancy outcomes achieved via the transfer of frozen euploid blastocysts.

Methods:

The study retrospectively analyzed 914 single euploid blastocyst transfer cycles that were performed at the Peking University Third Hospital Reproductive Medical Center between June 2011 and May 2016. The expansion, trophectoderm (TE), and inner cell mass (ICM) quality of the blastocysts were assessed based on blastocyst parameters, and used to differentiate between “excellent”, “good”, “average”, and “poor”-quality embryos. The relationship between these embryo grades and the achieved pregnancy outcomes was then analyzed via the Chi-square and logistic regression tests.

Results:

For embryo grades of excellent, good, average and poor, the clinical pregnancy rates were 65.0%, 59.3%, 50.3% and 33.3%, respectively; and the live-birth rates were 50.0%, 49.7%, 42.3% and 25.0%, respectively. Both the clinical pregnancy rate (χ² = 21.28, P = 0.001) and live-birth rate (χ² = 13.50, P < 0.001) increased with the overall blastocyst grade. Both rates were significantly higher after the transfer of a blastocyst that exhibited either an A-grade OR B-grade TE, and similarly, an A-grade ICM, than after the transfer of a blastocyst that exhibited a C-grade TE and/or ICM. The degree of blastocyst expansion had no apparent effect on the clinical pregnancy or live-birth rate. All odds ratio were adjusted for patient age, body mass index, length (years) of infertility history, and infertility type.

Conclusions:

A higher overall euploid blastocyst quality is shown to correlate most strongly with optimal pregnancy outcomes. The study thus supports the use of the described TE and ICM morphological grades to augment current embryo selection criteria.

Contraction behaviour reduces embryo competence in high-quality euploid blastocysts

PURPOSE

The aim of the study is to investigate how blastocyst contraction behaviour affects the reproductive competence in high-quality euploid embryos.

METHODS

Eight hundred ninety-six high-quality blastocysts derived from 190 patients (mean age 38.05 (SD = 2.9) years) who underwent preimplantation genetic testing for aneuploidies (PGT-A) from January 2016 to October 2017 were included in this study. PGT-A results were reported as euploid or aneuploid. Aneuploid embryos were sub-classified into three categories: monosomy, trisomy and complex aneuploid. Retrospective studies of time-lapse monitoring (TLM) of those embryos were analysed and reproductive outcome of transferred embryos was collected.

RESULTS

A total of 234/896 were euploid (26.1%) whilst 662/896 (73.9%) blastocysts were proven to be aneuploid from which 116 (17.6%) presented monosomies, 136 (20.5%) trisomies and 410 (61.9%) were complex aneuploid. The most frequent chromosomal complements were trisomies affecting chromosome 21 and monosomies involving chromosomes 16 and 22. Data analysis showed a statistical difference in the number of contractions being reported greater in aneuploid when compared to euploid embryos (0.6 vs 1.57; p < 0.001). Analysis of the aneuploid embryos showed that monosomies present less number of contractions when compared to embryos affected with trisomies or complex aneuploidies (1.23 vs 1.53 and 1.40; p < 0.05). No difference was observed when comparing the latter two groups. Euploid embryos presenting at least one contraction resulted in lower implantation and clinical pregnancy rates when compared to blastocysts that do not display this event (47.6 vs 78.5% and 40.0 vs 59.0% respectively).

CONCLUSIONS

Most aneuploid blastocysts diagnosed by PGT-A have complex aneuploidies, showing that aneuploid embryos can develop after genomic activation and reaching high morphological scores. It becomes clear that embryo contraction, despite being a physiological feature during blastulation, is conditioned by the ploidy status of the embryo. Furthermore, the presence of contractions may compromise implantation rates.

Relative Morphokinetics Assessed by Time-Lapse Imaging Are Altered in Embryos From Patients With Endometriosis

INTRODUCTION

Time-lapse technology allows almost continuous noninvasive assessment of embryonic development. It was shown previously that relative kinetics defining cleavage synchronicity are better predictors of blastocyst quality than absolute time points. This study aims to compare relative kinetics in embryos from patients with and without endometriosis.

METHODS

Time-lapse data were collected retrospectively from 596 patients undergoing infertility treatment for in vitro fertilization from January 2011 to July 2016. Four hundred twenty-eight patients with confounding comorbidities (ie, polycystic ovary syndrome, pathological spermiogram in the included cycle, numerical/structural genetic abnormalities, preimplantation genetic screening performed) or incomplete data sets were excluded. Of the 168 included patients, 72 (42.9%) had endometriosis. Indications for in vitro fertilization of controls were tubal factor, unexplained infertility, or prolonged infertility. Relative kinetics were calculated as defined previously: cleavage synchronicity (CS)2-8=((t3-t2) + (t5-t4))/(t8-t2), CS4-8=(t8-t5)/(t8-t4), CS2-4=(t4-t3)/(t4-t2), DNA replication time ratio (DR)=(t3-t2)/(t5-t3). In women with more than one embryo, the median time was analyzed.

RESULTS

Median age, body mass index, smoking status, and AMH levels were similar in both groups. Embryos from patients with endometriosis showed poorer relative kinetics. The relative time CS2-8 was decreased in embryos from patients with endometriosis (0.7 [0.0-0.93] vs 0.8 [0.0-0.94], P < .05) and CS4-8 was increased (0.4 [0.0-1.0] vs 0.3 [0.0-1.0], P < .05). The less powerful diagnostic relative kinetic parameters (CS2-4 and DR) were not significantly different.

CONCLUSIONS

Embryos from patients with endometriosis presented with altered relative kinetics suggesting poorer embryo quality. These findings support recently published data demonstrating reduced oocyte quality in patients with endometriosis which is one possible explanation for their poor response to fertility treatment.

Artificial blastocoel collapse of human blastocysts before vitrification and its effect on re-expansion after warming - a prospective observational study using time-lapse microscopy

Vitrified human blastocysts show varied re-expansion capacity after warming. This prospective observational study compared behaviour of artificially collapsed blastocysts (study group patients, n = 69) to that of blastocysts that were vitrified without artificial collapse (control group patients, n = 72). Warmed blastocysts were monitored by time-lapse microscopy and blastocoel re-expansion speed and growth patterns compared between study and control groups. These parameters were also retrospectively compared between blastocysts that resulted in live birth and those that failed. Artificially collapsed blastocysts re-expanded on average 15.01 µm²/min faster than control blastocysts (P = 0.0013). Warmed blastocysts expressed four different patterns of blastocoel growth. The pattern showing contractions at the end of culture was observed to have a lower prevalence in control blastocysts, which coincided with the lower incidence of hatching in this group. Re-expansion speed and prevalence of growth patterns were comparable between blastocysts that did and did not result in a live birth. This was seen in the study and control groups. Despite faster re-expansion and different growth patterns of artificially collapsed blastocysts, live birth rate did not differ between groups. However, this result should be interpreted with caution due to the small sample size and high risk of bias.