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

Abstract

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.

Morphokinetic features in human embryos: Analysis by our original high‐resolution time‐lapse cinematography—Summary of the past two decades

“…To date, there are few studies showing the benefits of using AI in the observation and evaluation of human embryo preimplantation dynamics. 48 , 75 , 76 , 77 By establishing valid and effective algorithms for time‐lapse incubators, we will be able to set stronger criteria that will qualify the prediction of normal growth and development potential of embryos, as well as the detection of aneuploidies, in order to avoid the application of invasive techniques such as preimplantation genetic testing.…”

“…However, spontaneous blastocoel collapse is generally considered to have a negative effect on embryonic development by the observation of hR‐TLC. 4 , 48 It has been confirmed that blastocysts with repeated major collapses have a high probability of poor subsequent development, failure to reach hatching and a lower live birth rate. Nevertheless, the blastocyst multiple collapse pattern is not recommended to be evaluated alone as a predictor of the reproductive outcome, but the morphokinetic variables should also be taken into account.…”

A brief history of artificial intelligence embryo selection: from black-box to glass-box

“…There are, however, alternative paths to address the transferability issue by utilizing more transferable qualitative TLV measures, such as abnormal cleavage ( Liu et al , 2020a ) or spontaneous blastocyst collapse ( Bickendorf et al , 2023 ). Annotation for embryo abnormal cleavage patterns is still mostly performed manually by an embryologist, while newer reports, such as on blastocyst spontaneous collapse ( Cimadomo et al , 2022 ), are starting to engage AI-powered tools to enable automated annotation. In fact, automated annotation is worth further attention considering its important role in both improvement of consistency and accuracy in annotating time-lapse images and maintaining better interpretability of embryo selection.…”

“…This progress, however, has purely focused on the annotation aspect without involving any ranking step. More recently, Cimadomo et al (2022) investigated blastocyst collapsing events in much detail by annotating start/end times of blastocyst collapse as well as the degree of blastocoel shrinkage. This study underlined blastocyst collapsing as a potential viability marker.…”

Y chromosome AZFc microdeletion may have negative effect on embryo euploidy: a retrospective cohort study

“…It is well known that the rate of aneuploid embryos increases dramatically with maternal age [ 3 ]. Several studies have assessed the relationship between embryo euploidy rates and ovarian stimulation process, culture conditions or the morphological features of blastocyst [ 4 – 6 ]. Although entire chromosomal aneuploidy in embryo originates mainly from meiotic errors during oocyte generation, approximately 8.1% of aneuploid embryos are still paternal in origin [ 7 ].…”