The human first cell cycle: impact on implantation

Automated Single-Sperm Selection Software (SiD) during ICSI: A Prospective Sibling Oocyte Evaluation

The computer-assisted program SiD was developed to assess and select sperm in real time based on motility characteristics. To date, there are limited studies examining the correlation between AI-assisted sperm selection and ICSI outcomes. To address this limit, a total of 646 sibling MII oocytes were randomly divided into two groups as follows: the ICSI group (n = 320): ICSI performed with sperm selected by the embryologist and the ICSI-SiD group (n = 326): ICSI performed with sperm selected using SiD software. Our results show a non-significant trend towards improved outcomes in the ICSI-SiD group across various biological parameters, including fertilization, cleavage, day 3 embryo development, blastocyst development, and quality on day 5. Similarly, we observed a non-significant increase in these outcomes when comparing both groups with sperm selection performed by a junior embryologist. Embryo development was monitored using a timelapse system. Some fertilization events happen significantly earlier when SiD is used for ICSI, but no significant difference was observed in the ICSI-SiD group for other timepoints. We observed comparable cumulative early and clinical pregnancy rates after ICSI-SiD. This preliminary investigation illustrated that employing the automated sperm selection software SiD leads to comparable biological outcomes, suggesting its efficacy in sperm selection.

Blastulation time measured with time-lapse system can predict in vitro viability of bovine blastocysts

The objective of this study was to evaluate the time of blastulation monitored by time-lapse technology to predict in vitro viability of bovine blastocysts. This technology can be a powerful tool for bovine embryos selection with higher implantation capacity and competence. Also, in humans an early blastulation is associated with higher quality and pregnancy rate. Cumulus oocyte complexes (COCs) were matured for 20 to 22 h and then fertilized by co-incubation of COCs and spermatozoa (10,000 sperm per oocyte) for 18 h. Presumptive zygotes were placed individually in microwells, in droplets of commercial culture medium. The Primo Vision TL system (EVO+; Vitrolife) captured digital images of developing embryos every 15 minutes. The time frame from IVF to the start of blastulation (tSB) and to blastocyst development (tB) was recorded. After day 7.5, the blastocysts were in vitro culture for 48 h until day 9.5 after IVF to evaluate post hatching development. In vitro viability was evaluated at day 9.5: those with a diameter greater than 200 μm and a total cell count greater than 180 were classified as viable (value 1), while the rest were classified as non in vitro viable (value 0). The area under the ROC curve (AUC) was estimated to determine the predictive power of in vitro viability through blastulation time. In addition, binary logistic regression analysis was used to generate a mathematical model with morphokinetic variables that allow the best prediction of in vitro viability. In 13 sessions, the blastocyst production rate was 46.2% (96/208). The cut-off time to discriminate early or late blastulation was 149.8 h. The post-hatching development of the embryos with early blastulation was 63.3% (31/49), being statistically superior (p = 0.001) than the late blastulation group 14.9% (7/47). Likewise, the time of blastulation showed an accuracy of 90.8% (p < 0.001) in predicting in vitro viability of bovine blastocysts. In conclusion, the selection of blastocysts based on blastulation time (< 155 h) and blastocyst diameter measured on day 7.5 after IVF (> 180 μm) maximizes the in vitro viability.

Sperm Chromatin Condensation Defect Accelerates the Kinetics of Early Embryonic Development but Does Not Modify ICSI Outcome

The origin and quality of gametes are likely to influence the kinetics of embryonic development. The purpose of the study was to assess the impact of sperm nuclear quality, and in particular sperm chromatin condensation, on the kinetics of early embryo development after intracytoplasmic sperm injection (ICSI). Our study included 157 couples who benefitted from ICSI for male factor infertility. Chromatin condensation and DNA fragmentation were assessed in spermatozoa prior to ICSI. Above the 20% threshold of sperm condensation defect, patients were included in the abnormal sperm chromatin condensation (ASCC) group; below the 20% threshold, patients were included in the normal sperm chromatin condensation (NSCC) group. After ICSI, the oocytes were placed in the time-lapse incubator. The kinetics of the cohort's embryonic development have been modeled. The fading times of pronuclei and the time to two blastomeres (t2, first cleavage) and four blastomeres (t4, third cleavage) differed significantly between the NSCC and ASCC groups, with earlier events occurring in the ASCC group. On the other hand, the state of sperm chromatin condensation did not seem to have an impact on live birth rates or the occurrence of miscarriages. The kinetics of early embryonic development was accelerated in males with a sperm chromatin condensation defect without compromising the chances of pregnancy or promoting miscarriage. However, our study highlights the paternal contribution to early embryonic events and potentially to the future health of the conceptus.

Non-invasive evaluation of embryo quality for the selection of transferable embryos in human in vitro fertilization-embryo transfer

The ultimate goal of human assisted reproductive technology is to achieve a healthy pregnancy and birth, ideally from the selection and transfer of a single competent embryo. Recently, techniques for efficiently evaluating the state and quality of preimplantation embryos using time-lapse imaging systems have been applied. Artificial intelligence programs based on deep learning technology and big data analysis of time-lapse monitoring system during in vitro culture of preimplantation embryos have also been rapidly developed. In addition, several molecular markers of the secretome have been successfully analyzed in spent embryo culture media, which could easily be obtained during in vitro embryo culture. It is also possible to analyze small amounts of cell-free nucleic acids, mitochondrial nucleic acids, miRNA, and long non-coding RNA derived from embryos using real-time polymerase chain reaction (PCR) or digital PCR, as well as next-generation sequencing. Various efforts are being made to use non-invasive evaluation of embryo quality (NiEEQ) to select the embryo with the best developmental competence. However, each NiEEQ method has some limitations that should be evaluated case by case. Therefore, an integrated analysis strategy fusing several NiEEQ methods should be urgently developed and confirmed by proper clinical trials.

Common dysmorphic oocytes and embryos in assisted reproductive technology laboratory in association with gene alternations

Amorphic or defected oocytes and embryos are commonly observed in assisted reproductive technology (ART) laboratories. It is believed that a proper gene expression at each stage of embryo development contributes to the possibility of a decent-quality embryo leading to successful implantation. Many studies reported that several defects in embryo morphology are associated with gene expressions during in vitro fertilization (IVF) treatment. There is lacking literature review on summarizing common morphological defects about gene alternations. In this review, we summarized the current literature. We selected 64 genes that have been reported to be involved in embryo morphological abnormalities in animals and humans, 30 of which were identified in humans and might be the causes of embryonic changes. Five papers focusing on associations of multiple gene expressions and embryo abnormalities using RNA transcriptomes were also included during the search. We have also reviewed our time-lapse image database with over 3000 oocytes/embryos to show morphological defects possibly related to gene alternations reported previously in the literature. This holistic review can better understand the associations between gene alternations and morphological changes. It is also beneficial to select important biomarkers with strong evidence in IVF practice and reveal their potential application in embryo selection. Also, identifying genes may help patients with genetic disorders avoid unnecessary treatments by providing preimplantation genetic testing for monogenic/single gene defects (PGT-M), reduce embryo replacements by less potential, and help scientists develop new methods for oocyte/embryo research in the near future.

Replication stress impairs chromosome segregation and preimplantation development in human embryos

Human cleavage-stage embryos frequently acquire chromosomal aneuploidies during mitosis due to unknown mechanisms. Here, we show that S phase at the 1-cell stage shows replication fork stalling, low fork speed, and DNA synthesis extending into G2 phase. DNA damage foci consistent with collapsed replication forks, DSBs, and incomplete replication form in G2 in an ATR- and MRE11-dependent manner, followed by spontaneous chromosome breakage and segmental aneuploidies. Entry into mitosis with incomplete replication results in chromosome breakage, whole and segmental chromosome errors, micronucleation, chromosome fragmentation, and poor embryo quality. Sites of spontaneous chromosome breakage are concordant with sites of DNA synthesis in G2 phase, locating to gene-poor regions with long neural genes, which are transcriptionally silent at this stage of development. Thus, DNA replication stress in mammalian preimplantation embryos predisposes gene-poor regions to fragility, and in particular in the human embryo, to the formation of aneuploidies, impairing developmental potential.

Fertilization signatures as biomarkers of embryo quality

Fertilization underpins the vital transition from gametic meiosis to embryonic mitosis. For decades, in human IVF, microscopic observation at a single time point has limited our appreciation of the morphokinetic complexity of this process. More recently, the introduction of time lapse technology-also enhanced by combination with artificial intelligence-has revealed the finest morphokinetic details of the beginning of human development. Overall, a picture has finally emerged in which the precise timing, morphology and geometry of several fertilization events offer clues to predict the fate of the embryo-a key aspect of assisted reproduction. In this scenario, correct unfolding of intra- and interpronuclear rearrangements emerge as a crucial factor to create a platform able to preserve genetic and cellular integrity at the first mitotic cleavage.

Pseudo contrastive labeling for predicting IVF embryo developmental potential

In vitro fertilization is typically associated with high failure rates per transfer, leading to an acute need for the identification of embryos with high developmental potential. Current methods are tailored to specific times after fertilization, often require expert inspection, and have low predictive power. Automatic methods are challenged by ambiguous labels, clinical heterogeneity, and the inability to utilize multiple developmental points. In this work, we propose a novel method that trains a classifier conditioned on the time since fertilization. This classifier is then integrated over time and its output is used to assign soft labels to pairs of samples. The classifier obtained by training on these soft labels presents a significant improvement in accuracy, even as early as 30 h post-fertilization. By integrating the classification scores, the predictive power is further improved. Our results are superior to previously reported methods, including the commercial KIDScore-D3 system, and a group of eight senior professionals, in classifying multiple groups of favorable embryos into groups defined as less favorable based on implantation outcomes, expert decisions based on developmental trajectories, and/or genetic tests.

Time-Lapse Systems: A Comprehensive Analysis on Effectiveness

Time-lapse systems have quickly become a common feature of in vitro fertilization laboratories all over the world. Since being introduced over a decade ago, the alleged benefits of time-lapse technology have continued to grow, from undisturbed culture conditions and round the clock, noninvasive observations to more recent computer-assisted selection of embryos through the development of algorithms. Despite the global uptake of time-lapse technology, its real impact on clinical outcomes is still controversial. This review aims to explore the different features offered by time-lapse technology, discussing incubation, algorithms, artificial intelligence and the regulation of nonessential treatment interventions, while assessing evidence on whether any benefit is offered over conventional technology.

Morphometric and morphokinetic differences in the sperm- and oocyte-originated pronuclei of male and female human zygotes: a time-lapse study

PURPOSE

To study the morphometric and morphokinetic profiles of pronuclei (PN) between male and female human zygotes.

METHOD(S)

This retrospective cohort study included 94 consecutive autologous single day 5 transfer cycles leading to a singleton live birth. All oocytes were placed in the EmbryoScope + incubator post-sperm injection with all annotations performed retrospectively by one embryologist (L-SO). Timing parameters included 2nd polar body extrusion (tPB2), sperm-originated PN (tSPNa) or oocyte-originated PN (tOPNa) appearance, and PN fading (tPNF). Morphometrics were evaluated at 8 (stage 1), 4 (stage 2), and 0 h before PNF (stage 3), measuring PN area (um²), PN juxtaposition, and nucleolar precursor bodies (NPB) arrangement.

RESULTS

Male zygotes had longer time intervals of tPB2_tSPNa than female zygotes (4.8 ± 0.2 vs 4.2 ± 0.1 h, OR = 1.442, 95% CI 1.009-2.061, p = 0.044). SPN increased in size from stage 1 through 2 to 3 (435.3 ± 7.2, 506.7 ± 8.0, and 556.3 ± 8.9 um², p = 0.000) and OPN did similarly (399.0 ± 6.1, 464.3 ± 6.7, and 513.8 ± 6.5 um², p = 0.000), with SPN being significantly larger than OPN at each stage (p < 0.05 respectively). More male than female zygotes reached central PN juxtaposition at stage 1 (76.7% vs 51.0%, p = 0.010), stage 2 (97.7% vs 86.3%, p = 0.048), and stage 3 (97.7% vs 86.3%, p = 0.048). More OPN showed aligned NPBs than in SPN at stage 1 only (44.7% vs 28.7%, p = 0.023).

CONCLUSION(S)

Embryos with different sexes display different morphokinetic and morphometric features at the zygotic stage. Embryo selection using such parameters may lead to unbalanced sex ratio in resulting offspring.

Spatiotemporal perturbations of pronuclear breakdown preceding syngamy affect early human embryo development: a retrospective observational study

PURPOSE

During fertilisation, female and male pronuclei (PNs) migrate to the centre of the ooplasm, juxtapose, and break down synchronously in preparation for the first mitosis. While PN non-juxtaposition and PN breakdown (PNBD) asynchrony are occasionally observed, their developmental implications remain uncertain. This study investigated the possible relationships among the two phenomena, preimplantation development patterns, and live birth rates in single blastocyst transfers.

METHODS

A total of 1455 fertilised oocytes cultured in a time-lapse incubator were retrospectively analysed. Fertilised oocytes were divided into four groups according to the presence of PN juxtaposition and breakdown synchrony. The relationships of abnormal PN behaviour with embryo morphokinetics, blastocyst formation, and live birth were evaluated.

RESULTS

PN non-juxtaposition and asynchrony were observed in 1.9% and 1.0% of fertilised oocytes, respectively. The blastocyst cryopreservation rates in the synchronous-non-juxtaposed and asynchronous-non-juxtaposed groups were significantly lower than that in the synchronous-juxtaposed group. The rates of clinical pregnancy, ongoing pregnancy, and live birth were comparable among the groups. Non-juxtaposition was significantly associated with increased trichotomous cleavage at the first cytokinesis (P < 0.0001) and an increase in the time interval from PNBD to first cleavage (P < 0.0001). Furthermore, asynchronous PNBD was significantly correlated with increased rapid cleavage at the first cytokinesis (P = 0.0100).

CONCLUSION

Non-juxtaposition and asynchronous PNBD is associated with abnormal mitosis at the first cleavage and impaired preimplantation development. However, embryos displaying abnormal PNBD may develop to blastocyst stage and produce live births, suggesting blastocyst transfer as a more appropriate culture strategy.

Characteristics of the cytoplasmic halo during fertilisation correlate with the live birth rate after fresh cleaved embryo transfer on day 2 in minimal ovarian stimulation cycles: a retrospective observational study

BACKGROUND

Information regarding the influence of cytoplasmic events during fertilisation on the clinical outcome remains limited. The cytoplasmic halo is one of these events. A previous study that used time-lapse technology found an association of the presence and morphokinetics of the cytoplasmic halo with cleavage patterns, development to the blastocyst stage, and the ongoing pregnancy rate after blastocyst transfer. Therefore, the cytoplasmic halo may be a useful predictor of the pregnancy outcome after cleaved embryo transfer. This study evaluated the ability of the cytoplasmic halo to predict a live birth after fresh cleaved embryo transfer on day 2, and sought to identify factors potentially influencing the presence and morphokinetics of the halo.

METHODS

A total of 902 embryos cultured in the EmbryoScope+® time-lapse system and subjected to single fresh cleaved embryo transfer were retrospectively analysed. The presence and duration of a cytoplasmic halo were annotated. The initial positions of the pronuclei were also observed. The correlation between the cytoplasmic halo and live birth was evaluated and the association of the cytoplasmic halo with patient, cycle, and embryonic characteristics was determined.

RESULTS

Absence of a cytoplasmic halo was associated with a significant decrease in the likelihood of a live birth after fresh cleaved embryo transfer. Prolongation of the halo, especially the duration of central repositioning of cytoplasmic granules, had an adverse impact on the live birth rate. The characteristics of the cytoplasmic halo were not affected by the ovarian stimulation method used, female age, the serum steroid hormone level on the day of trigger, or semen quality. However, the cytoplasmic halo was significantly affected by male age, oocyte diameter, and the initial position of the male pronucleus.

CONCLUSIONS

Absence or prolongation of the cytoplasmic halo was negatively correlated with the live birth rate after fresh cleaved embryo transfer. The characteristics of the cytoplasmic halo were strongly associated with oocyte diameter, male age, and the initial position of the male pronucleus. These findings indicate that the characteristics of the cytoplasmic halo can be used to select more competent embryos for transfer at the cleavage stage.

Optimisation of the timing of fertilisation assessment for oocytes cultured in standard incubation: lessons learnt from time-lapse imaging of 78 348 embryos

STUDY QUESTION

Using time-lapse data, can the current consensus for the timing of fertilisation assessment of oocytes, cultured in standard incubation, be optimised?

SUMMARY ANSWER

The optimum time to perform fertilisation assessment for oocytes cultured in standard incubation is 16.5 ± 0.5 h post-insemination (hpi), and the current consensus requires modification in order to minimise the chance of fertilisation being missed.

WHAT IS KNOWN ALREADY

Time-lapse incubation allows the embryologist to retrospectively review collated images of oocytes and embryos to capture important embryological observations that may otherwise be missed in standard incubation. According to expert consensus, the optimum time to perform the assessment of fertilisation is 17 ± 1 hpi.

STUDY DESIGN, SIZE, DURATION

A retrospective, multicentre analysis utilised data obtained from 54 746 ICSI-derived embryos and 23 602 IVF-derived embryos cultured in time-lapse incubation between January 2011 and November 2019.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Using time-lapse imaging (TLI), the precise time of pronuclei appearance and disappearance was recorded, where applicable, and the number of oocytes with two pronuclei observable during 10 30-min intervals from 15 hpi to 20 hpi was determined.

MAIN RESULTS AND THE ROLE OF CHANCE

Between 15 and 17.5 hpi, the average number of oocytes exhibiting normal fertilisation, elicited as two pronuclei, was 98.19% with the highest proportion of oocytes having visible pronuclei at 16-16.5 hpi (98.32%). At 18-18.5 hpi, the number of visible pronuclei reduced to 95.53% and continued to fall to 87.02% at 19.5-20 hpi.

LIMITATIONS, REASONS FOR CAUTION

The authors' expectation is that these findings are transferable to other settings, however it is possible that, with alternative culture media and incubation environments, calibration of this timing may be required. As data cannot readily be recorded for pronuclear appearance for IVF-derived embryos, it is not possible to determine the optimum time to perform the fertilisation assessment for IVF-derived embryos.

WIDER IMPLICATIONS OF THE FINDINGS

By fine-tuning the time at which fertilisation assessment takes place the accuracy of the assessment can be increased to maximise the number of fertilised oocytes identified, thereby increasing the number of usable embryos for the patient. Without TLI and following current consensus guidelines, over 11% (n = 3000) of oocytes would have been marked as unfertilised within this cohort. Further to this, depending on the time of a standard fertilisation assessment, up to 300 embryos which resulted in live births could have been categorised as unfertilised, as they presented no visible pronuclei at the conventional assessment time-point.

STUDY FUNDING/COMPETING INTEREST(S)

A.C. is a minor shareholder in CARE Fertility Limited. Validated algorithmic time-lapse embryo selection is offered to patients at CARE Fertility at an additional charge as an adjuvant treatment option.

TRIAL REGISTRATION NUMBER

N/A.

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.

Time-lapse monitoring of fertilized human oocytes focused on the incidence of 0PN embryos in conventional in vitro fertilization cycles

We aimed to investigate why the incidence of embryos derived from oocytes with no pronuclei (0PN) decreases using time-lapse monitoring (TLM) versus fixed-point assessment in conventional IVF cycles. We analyzed 514 embryos monitored with TLM 6–9 h after insemination and 144 embryos monitored using microscopic assessment 18–21 h after insemination. The primary endpoint of this study was the incidence of 0PN-derived embryos in short insemination followed by TLM. The secondary endpoint was the duration of insemination. As exploratory endpoints, we analyzed the blastulation rate and cryo-warmed blastocyst transfer outcome of embryos with early PN fading, whereby PN disappeared within < 20 h following the initiation of insemination. The incidence of 0PN-derived embryo reduced more significantly through TLM than through fixed-point observation. The microscopic assessment time was more significantly delayed in the 0PN-derived embryo than that in the 2PN-derived embryo. The embryo with early PN fading formed good-quality blastocysts, and their pregnancy outcomes were similar to those of other embryos. Most 0PN-derived embryos in the fixed-point assessment might have resulted from missed observation of PN appearance in the early-cleaved embryos. TLM or strict laboratory schedule management may reduce 0PN-derived embryos by reducing missed PN observations.

Melatonin improves the first cleavage of parthenogenetic embryos from vitrified-warmed mouse oocytes potentially by promoting cell cycle progression

Background

This study investigated the effect of melatonin (MT) on cell cycle (G1/S/G2/M) of parthenogenetic zygotes developed from vitrified-warmed mouse metaphase II (MII) oocytes and elucidated the potential mechanism of MT action in the first cleavage of embryos.

Results

After vitrification and warming, oocytes were parthenogenetically activated (PA) and in vitro cultured (IVC). Then the spindle morphology and chromosome segregation in oocytes, the maternal mRNA levels of genes including Miss, Doc1r, Setd2 and Ythdf2 in activated oocytes, pronuclear formation, the S phase duration in zygotes, mitochondrial function at G1 phase, reactive oxygen species (ROS) level at S phase, DNA damage at G2 phase, early apoptosis in 2-cell embryos, cleavage and blastocyst formation rates were evaluated. The results indicated that the vitrification/warming procedures led to following perturbations 1) spindle abnormalities and chromosome misalignment, alteration of maternal mRNAs and delay in pronucleus formation, 2) decreased mitochondrial membrane potential (MMP) and lower adenosine triphosphate (ATP) levels, increased ROS production and DNA damage, G1/S and S/G2 phase transition delay, and delayed first cleavage, and 3) increased early apoptosis and lower levels of cleavage and blastocyst formation. Our results further revealed that such negative impacts of oocyte cryopreservation could be alleviated by supplementation of warming, recovery, PA and IVC media with 10^− 9 mol/L MT before the embryos moved into the 2-cell stage of development.

Conclusions

MT might promote cell cycle progression via regulation of MMP, ATP, ROS and maternal mRNA levels, potentially increasing the first cleavage of parthenogenetic zygotes developed from vitrified–warmed mouse oocytes and their subsequent development.

Plasticity of the human preimplantation embryo: developmental dogmas, variations on themes and self-correction

BACKGROUND

IVF for the treatment of infertility offers unique opportunities to observe human preimplantation development. Progress in time-lapse technology (TLT) and preimplantation genetic testing (PGT) has greatly expanded our knowledge of developmental patterns leading to a healthy pregnancy or developmental failure. These technologies have also revealed unsuspected plastic properties of the preimplantation embryo, at macromolecular, cellular and multicellular levels.

OBJECTIVE AND RATIONALE

This review focuses on the emerging concept of plasticity of the human embryo as revealed by recent evidence derived from TLT and PGT, calling for an updated and more precise redefinition of the boundaries between normal and abnormal development.

SEARCH METHODS

PubMed was used to search the MEDLINE database for peer-reviewed English-language original articles and reviews concerning human preimplantation development. Cross-searches were performed by adopting 'fertilisation', 'pronucleus', 'cleavage', 'multinucleation', 'compaction', 'embryo', 'preimplantation genetic testing', 'aneuploidy', mosaicism', 'micromanipulation', 'time-lapse microscopy' and 'IVF/assisted reproduction' as main terms. The most relevant publications, i.e. those concerning major phenomena occurring during normal and abnormal development-with a focus on the human species-were assessed and discussed critically.

OUTCOMES

Advances in TLT and PGT have revealed an astonishing plasticity and self-correction ability of the human preimplantation embryo in vitro. At fertilisation, an abnormal number of pronuclei do not always result in the formation of an aneuploid blastocyst. Animal studies and preliminary human observations indicate that combining of parental genomes may occur at the early cleavage stage, if not at fertilisation. Multinucleation occurs with much higher prevalence than previously thought and may be corrected at later cleavage stages. Irregular cleavage (multichotomous, direct, rapid and reverse cleavages) can generate chromosome segregation abnormalities that often lead to developmental arrest, but that sporadically may be confined to cells excluded from the blastocyst, and may sometimes result in viable pregnancy. Mitotic errors can generate mosaic blastocysts, but alternatively normal embryos may form from selective death or clonal depletion of aneuploid cells.

WIDER IMPLICATIONS

Deviations from developmental dogmas and the increasing evidence of plasticity of the human embryo challenge current embryological notions and suggest the need to write new rules governing cell cycle, cell determination and chromosome segregation during preimplantation development.

Migration speed of nucleolus precursor bodies in human male pronuclei: a novel parameter for predicting live birth

PURPOSE

To study the relationship between the migration speed of nucleolus precursor bodies (NPBs) in male and female pronuclei (mPN; fPN) and human embryo development during assisted reproduction.

METHODS

The migration speed of 263 NPBs from 47 zygotes was quantitated, and embryonic development was observed until the blastocyst stage. The central coordinates of mPN, fPN, and NPBs were noted at multiple timepoints. Then, the distance traveled by the NPBs between two sequential images was measured, and migration speed was calculated. Additionally, we investigated the relationship between NPB migration speed and ploidy status (N = 33) or live birth/ongoing pregnancy (LB/OP) (N = 60) after assisted reproduction.

RESULTS

The NPB migration speed in both mPN and fPN was significantly faster in the zygotes that developed into blastocysts (N = 25) than that in the zygotes that arrested (N = 22). The timing of blastulation was negatively correlated with NPB migration speed in the mPN. Faster NPB migration was significantly correlated with LB/OP. In multivariate logistic analysis, NPB migration speed in the mPN was the only morphokinetic parameter associated with LB/OP. In a receiver-operating characteristic curve analysis of LB/OP by the NPB migration speed in the mPN, the cut-off value was 4.56 μm/h. When this cut-off value was applied to blastocysts with preimplantation genetic testing for aneuploidy, 100% of the blastocysts faster than or equal to the cut-off value were euploid.

CONCLUSION

The NPBs migrated faster in zygotes having the potential to develop into a blastocyst, and eventually into a baby. This predictor could be an attractive marker for non-invasive embryo selection.

Morphokinetic analysis of pronuclei using time-lapse cinematography in bovine zygotes

The morphokinetics of pronuclei (PN) are considered crucial factors affecting embryogenesis in mammals. Whereas, since bovine zygotes contain a large number of cytosolic lipid droplets, detailed observation of PN has not been performed. In this study, we visualized PN using time-lapse cinematography (TLC) with light microscopy for the first time in delipidated bovine zygotes. The proportions of 0 PN, 1PN, 2PN, and multi-PN in delipidated bovine zygotes were 10.1%, 6.5%, 72.7%, and 10.8%, respectively. Abnormal fertilization, including 1 PN and multi-PN, was observed in 15.6% of blastocysts. The times from IVF to PN appearance, PN fading, and first cleavage in 2 PN bovine zygotes that developed into blastocysts were 10.4, 25.5, and 27.6 h, respectively, which were similar to PN morphokinetics in humans. The 2 PN zygotes showed that the prolonged time from IVF to the appearance of PN and from the fading of PN to the first cleavage negatively affected blastocyst formation. The time from appearance to fading of PN in multi-PN zygotes that developed into blastocysts was longer than that in multi-PN zygotes that did not develop into blastocysts. Besides, among zygotes that developed into blastocysts, the time from appearance to fading of PN in multi-PN zygotes was longer than that in 2 PN and 1 PN zygotes. These results suggest that PN morphokinetic abnormalities are associated with subsequent embryonic development. Observation of PN in bovine zygotes by using non-invasive visible light TLC by delipidation could be a powerful tool to clarify the relationship between PN morphokinetics and developmental competence.

Use of time-lapse monitoring in medically assisted reproduction treatments: a mini-review

During human in vitro culture, a morphological microscope analysis is normally performed to select the best embryo to transfer, with the hope of obtaining a successful pregnancy. The morphological evaluation may combine number and size of blastomeres, fragmentation, multinucleation, blastocyst expansion, inner-cell mass and trophectoderm appearance. However, standard microscopy evaluation involves the removal of the embryos from the incubator, exposing them to changes in pH, temperature, and oxygen level. Additionally, morphological assessments might include high inter-observer variability. Recently, continuous embryo culture using time-lapse monitoring (TLM) has allowed embryologists to analyse the dynamic and morphokinetic events of embryo development and, based on that, the embryologist is able to scrutinize the complete sequence of embryonic evolution, from fertilization to the blastocyst formation. Therefore, TLM allows an uninterrupted culture condition, reducing the need to remove embryos from the incubator. The monitoring system is normally composed of a standard incubator with an integrated microscope coupled to a digital camera, which is able to collect images at regular times, and subsequently processed into video. These data can be annotated and analyzed using an integrated software, therefore this allows embryologists to facilitate the process of embryo selection for transfer. The main aim of this paper is to discuss the potential benefits and uses of the TLM in the embryology laboratory.

Time-lapse imaging derived morphokinetic variables reveal association with implantation and live birth following in vitro fertilization: A retrospective study using data from transferred human embryos

The purpose of this retrospective time-lapse data analysis from transferred preimplantation human embryos was to identify early morphokinetic cleavage variables that are related to implantation and live birth following in vitro fertilization (IVF). All embryos were monitored from fertilization check until embryo transfer for a minimum of 44 hours. The study was designed to assess the association between day 2 embryo morphokinetic variables with implantation and live birth based on Known Implantation Data (KID). The kinetic variables were subjected to quartile-based analysis. The predictive ability for implantation and live birth was studied using receiver operator characteristic (ROC) curves. Three morphokinetic variables, time to 2-cells (t2), duration of second cell cycle (cc2) below one threshold and cc2 above another threshold had the highest predictive value with regards to implantation and live birth following IVF treatment. The predictive pre-transfer information has little divergence between fetal heartbeat and live birth data and therefore, at least for early morphokinetic variables up to the four-cell stage (t4), conclusions and models based on fetal heartbeat data can be expected to be valid for live birth datasets as well. The three above mentioned variables (t2, cc2 below one threshold and cc2 above another threshold) may supplement morphological evaluation in embryo selection and thereby improve the outcome of in vitro fertilization treatments.

Novel and conventional embryo parameters as input data for artificial neural networks: an artificial intelligence model applied for prediction of the implantation potential

OBJECTIVE

To describe novel embryo features capable of predicting implantation potential as input data for an artificial neural network (ANN) model.

DESIGN

Retrospective cohort study.

SETTING

University-affiliated private IVF center.

PATIENT(S)

This study included 637 patients from the oocyte donation program who underwent single-blastocyst transfer during two consecutive years.

INTERVENTION(S)

None.

MAIN OUTCOME MEASURE(S)

The research was divided into two phases. Phase 1 consisted of the description and analysis of the following embryo features in implanted and nonimplanted embryos: distance and speed of pronuclear migration, blastocyst expanded diameter, inner cell mass area, and trophectoderm cell cycle length. Phase 2 consisted of the development of an ANN algorithm for implantation prediction. Results were obtained for four models fed with different input data. The predictive power was measured with the use of the area under the receiver operating characteristic curve (AUC).

RESULT(S)

Out of the five novel described parameters, blastocyst expanded diameter and trophectoderm cell cycle length had statistically different values in implanted and nonimplanted embryos. After the ANN models were trained and validated using fivefold cross-validation, they were capable of predicting implantation on testing data with AUCs of 0.64 for ANN1 (conventional morphokinetics), 0.73 for ANN2 (novel morphodynamics), 0.77 for ANN3 (conventional morphokinetics + novel morphodynamics), and 0.68 for ANN4 (discriminatory variables from statistical test).

CONCLUSION(S)

The novel proposed embryo features affect the implantation potential, and their combination with conventional morphokinetic parameters is effective as input data for a predictive model based on artificial intelligence.

Can novel early non-invasive biomarkers of embryo quality be identified with time-lapse imaging to predict live birth?

STUDY QUESTION

Can time-lapse imaging systems make it possible to identify novel early non-invasive biomarkers to predict live birth?

SUMMARY ANSWER

From mostly high-grade embryos, out of 35 morphometric, morphologic and morphokinetic variables, only pronuclei (PN) position at time of PN juxtaposition and the absence of multinucleated blastomeres at the 2-cell stage (MNB2cell), were potentially associated with live birth.

WHAT IS KNOWN ALREADY

Previous studies indicate that some kinetic markers may be predictive of blastocyst development and embryonic implantation. Certain teams have suggested including some of them in decisional algorithms for embryo transfers.

STUDY DESIGN, SIZE, DURATION

Using a time-lapse incubator (EmbryoScope, Unisense FertiliTech), we retrospectively explored the associations between the morphometric, morphologic and morphokinetic parameters of oocytes, zygotes and embryos, and their associations with live birth. This study assessed 232 embryos from single embryo transfers after ICSI cycles performed between January 2014 and December 2017.

PARTICIPANTS/MATERIALS, SETTING, METHODS

The morphometric, morphologic and morphokinetic parameters (18, 4 and 13, respectively) of oocytes, zygotes and early embryos were studied retrospectively. The associations between these parameters were examined using a Spearman's correlation, Mann-Whitney or chi-squared test as appropriate. We examined whether these parameters were associated with outcomes in univariate and multivariate logistic regression analyses.

MAIN RESULTS AND THE ROLE OF CHANCE

Central PN juxtaposition was associated with a 2-fold increase in the odds of live birth (OR = 2.20; 95% CI, [1.26-3.89]; P = 0.006), while the presence of MNB2cell was associated with half the odds of live birth (OR = 0.51; 95% CI, [0.27-0.95]; P = 0.035). These two parameters were independent of embryo kinetics. The 33 remaining parameters had no significant association with the capacity of transferred embryos to develop to term.

LIMITATIONS, REASONS FOR CAUTION

Even though the population size was relatively small, our analyses were based on homogeneous cycles, i.e. young women whose transferred embryos were found to be high-grade according to conventional morphology evaluation. In addition, our conclusions were established from a specific, highly selected population, so other study populations, such as women in an older age bracket, may yield different results. Finally, because we assessed day 2/3 transfers, our findings cannot be generalized to embryos cultured up to the blastocyst stage.

WIDER IMPLICATIONS OF THE FINDINGS

It would be interesting to explore, prospectively, whether PN localisation is a relevant measure to predict embryo development when added into further algorithms and whether this parameter could be suitable for use in other IVF clinics. Further studies are needed, notably to explore the added value of timing evaluation in cohorts of embryos with low or intermediate morphology grade, as well as in other maternal populations (i.e. older women).

STUDY FUNDING/COMPETING INTEREST(S)

No external funding was used for this study. P. Sagot received funding from the following commercial companies: Merck Serono, Finox Biotech, Ferring, MSD France SAS, Teva Sante ́ SAS, Allergan France, Gedeon Richter France, Effik S.A., Karl Storz Endoscopie France, GE Medical Systems SCS, Laboratoires Genevrier, H.A.C. Pharma and Ipsen.All the authors confirm that none of this funding was used to support the research in this study. There are no patents, products in development or marketed products to declare. This does not alter the authors' adherence to all the journal policies on sharing data and materials.

Morphokinetics and in vitro developmental potential of monopronucleated ICSI zygotes until the blastocyst stage

The aim of this study was to provide a more comprehensive understanding of 1PN intracytoplasmic sperm injection (ICSI) zygotes. To achieve this objective, we assessed whether all 1PN-derived embryos showed a similar morphokinetic pattern, and if the morphokinetic behaviour of 1PN-derived embryos was comparable with that of 2PN-derived embryos. In total, 149 1PN ICSI zygotes (study group) and 195 2PN ICSI zygotes (control group) were included in the study. Embryo development potential was evaluated in terms of blastocyst rate. Morphokinetic parameters, including the pronucleus diameter and kinetics of in vitro development, were also analyzed. Embryos derived from 1PN ICSI zygotes showed impaired development compared with 2PN-derived embryos, with blastocyst rates of 28.9% and 67.2%, respectively. The diameter of the pronucleus of 1PN zygotes was larger than that of 2PN zygotes. When compared with 2PN-derived embryos, those derived from 1PN zygotes had a visible pronucleus for a shorter time, in addition to a longer syngamy time and slower kinetic behaviour from two to nine cells. When 1PN-derived blastocysts and 2PN-derived blastocysts were compared, the developmental kinetics were similar in both groups, except for a delayed and longer duration of the compaction phase in 1PN-derived embryos. In conclusion, monopronucleated ICSI zygotes present differences in developmental capacity and morphokinetic behaviour compared with 2PN ICSI zygotes, showing particular morphokinetic parameters related to pronucleus formation. Only the 1PN ICSI-derived embryos that reached the blastocyst stage have similar morphokinetic development to blastocysts from 2PN zygotes.

Fertilization and Cleavage Axes Differ In Primates Conceived By Conventional (IVF) Versus Intracytoplasmic Sperm Injection (ICSI)

With nearly ten million babies conceived globally, using assisted reproductive technologies, fundamental questions remain; e.g., How do the sperm and egg DNA unite? Does ICSI have consequences that IVF does not? Here, pronuclear and mitotic events in nonhuman primate zygotes leading to the establishment of polarity are investigated by multidimensional time-lapse video microscopy and immunocytochemistry. Multiplane videos after ICSI show atypical sperm head displacement beneath the oocyte cortex and eccentric para-tangential pronuclear alignment compared to IVF zygotes. Neither fertilization procedure generates incorporation cones. At first interphase, apposed pronuclei align obliquely to the animal-vegetal axis after ICSI, with asymmetric furrows assembling from the male pronucleus. Furrows form within 30° of the animal pole, but typically, not through the ICSI injection site. Membrane flow drives polar bodies and the ICSI site into the furrow. Mitotic spindle imaging suggests para-tangential pronuclear orientation, which initiates random spindle axes and minimal spindle:cortex interactions. Parthenogenetic pronuclei drift centripetally and assemble astral spindles lacking cortical interactions, leading to random furrows through the animal pole. Conversely, androgenotes display cortex-only pronuclear interactions mimicking ICSI. First cleavage axis determination in primates involves dynamic cortex-microtubule interactions among male pronuclei, centrosomal microtubules, and the animal pole, but not the ICSI site.

Adverse effects of paternal obesity on the motile spermatozoa quality

Growing evidence suggests that paternal obesity may decrease male fertility potential. During infertility treatment with intra-cytoplasmic sperm injection (ICSI), a morphologically normal motile spermatozoon is injected into a mature egg, when possible. However, sperm motility and morphology per se do not reflect the sperm molecular composition. In this study, we aimed to assess the quality of motile spermatozoa in the context of obesity by analysing their conventional and molecular characteristics as well as their ability to promote early embryonic development. A prospective study was conducted on 128 infertile men divided into three groups: 40 lean, 42 overweight, and 46 obese men. Conventional sperm parameters (concentration, motility and morphology) and sperm molecular status (chromatin composition and integrity, 5-methycytosine (5-mC) and 5-hydroxycytosine (5-hmC) contents and oxidative stress level) were analysed on raw semen and/or on motile spermatozoa selected by density gradient or swim-up techniques. Morphokinetic analysis of the embryos derived from ICSI was performed using the Embryoviewer software. Our results showed that the motile sperm-enriched fraction from obese men exhibited higher levels of retained histones (p<0.001), elevated percentage of altered chromatin integrity (p<0.001), and decreased contents of 5-hmC (p<0.001), and 5-mC (p<0.05) levels as compared to that from lean men. Importantly, there were no statistically significant correlations between these molecular parameters and the percentages of morphologically normal motile spermatozoa. Regarding embryo morphokinetics, the CC1 (p<0.05) and CC3 (p<0.05) embryonic cell cycles were significantly delayed in the cleavage embryos of the obese group as compared to the embryos of the lean group. Our data is of particular interest because, besides demonstrating the negative impacts of obesity on motile spermatozoa molecular composition, it also highlights the possible risk of disturbing early embryonic cell cycles kinetics in the context of paternal obesity.

Focused time-lapse analysis reveals novel aspects of human fertilization and suggests new parameters of embryo viability

STUDY QUESTION

Can focused application of time-lapse microscopy (TLM) lead to a more detailed map of the morphokinetics of human fertilization, revealing novel or neglected aspects of this process?

SUMMARY ANSWER

Intensive harnessing of TLM reveals novel or previously poorly characterised phenomena of fertilization, such as a cytoplasmic wave (CW) preceding pronuclear formation and kinetics of pronuclear chromatin polarization, thereby suggesting novel non-invasive biomarkers of embryo quality.

WHAT IS KNOWN ALREADY

In recent years, human preimplantation development has been the object of TLM studies with the intent to develop morphokinetic algorithms able to predict blastocyst formation and implantation. Regardless, our appreciation of the morphokinetics of fertilization remains rather scarce, currently including only times of polar body II (PBII) emission, pronuclear appearance and fading, and first cleavage. This is not consistent with the complexity and importance of this process, calling for further TLM studies aimed at describing previously unrecognized or undetected morphokinetic events and identifying novel developmental biomarkers.

STUDY DESIGN, SIZE, DURATION

The study involved a retrospective observation by TLM of the fertilization process in 500 oocytes utilized in consecutive ICSI cycles carried out in 2016. A maximum of five fertilized oocytes per patients were included in the analysis to reduce possible patient-specific biases. Oocytes of patients with different diagnoses of infertility where included in the analysis, while cases involving cryopreserved gametes or surgically retrieved sperm were excluded.

PARTICIPANTS/MATERIALS, SETTINGS, METHODS

Microinjected oocytes where assessed by a combined TLM-culture system (Embryoscope). Oocytes that were not amenable to TLM assessment, due to excess of residual corona cells or inadequate orientation for the observation of PBII emission, were not analysed. We identified and monitored 28 parameters relevant to meiotic resumption, pronuclear dynamics, chromatin organization, and cytoplasmic/cortical modifications. Times (T) were expressed as mean ± SD hours post-insemination (p.i.) and analysed, where appropriate, by Paired T Student or Fisher's exact tests.

MAIN RESULTS AND ROLE OF CHANCE

PBII emission was occasionally followed (4.3% of cases) by the transient appearance of a protrusion of the cell surface, the fertilization cone (FC), probably resulting from interaction of the male chromatin with the oocyte cortex. Pronuclear formation was always preceded by a radial CW originating from the initial position of the male pronucleus (PN) and extending towards the oocyte periphery. The appearance of the CW followed a precise sequence, occurring always 2-3 h after PBII emission and shortly before PN appearance. Male and female PN appeared virtually simultaneously at approximately 6.2 h p.i. However, while the female PN always formed cortically and near the site of emission of the PBII, the initial position of the male PN was cortical, intermediate, or central (15.2%, 31.2% and 53.6%, respectively). PN juxtaposition involved rapid and straight movement of the female PN towards the male PN. In addition, the initial position of male PN formation was predictive of the position of PN juxtaposition. It was also observed that nucleolar precursor bodies (NPBs) aligned along the juxtaposition area and this happened considerably earlier for the female PN (8.2 ± 2.6 vs.11.2 ± 4.1 h, P = 0.0001). Although it occurred rarely, displacement of juxtaposed PN to the cortex was strongly associated (P < 0.0001) with direct cleavage into three blastomeres at the first cell division. The times of PN breakdown and first cleavage showed a very consistent trend, occurring earlier or progressively later depending on whether initial male PN positioning was central, intermediate or cortical, respectively. Finally, time intervals between discrete fertilization events were strongly associated with embryo quality on Day 3. For example, longer intervals between disappearance of the cytoplasmic halo and PN breakdown were highly predictive of reduced blastomere number and increased fragmentation (P = 0.0001).

LARGE SCALE DATA

N/A.

LIMITATIONS, REASON FOR CAUTION

Some of the morphokinetic parameters assessed in this study may require better definition to reduce inter-operator annotation variability.

WIDER IMPLICATIONS OF THE FINDINGS

To our knowledge, overall, these data represent the most detailed morphokinetic description of human fertilization. Many of the illustrated parameters are novel and may be amenable to further elaboration into algorithms able to predict embryo quality, as suggested by the findings presented in this study.

STUDY FUNDING/COMPETING INTERESTS

None.

Time-lapse imaging reveals delayed development of embryos carrying unbalanced chromosomal translocations

PURPOSE

The purpose of the study was to compare the morphokinetic parameters of embryos carrying balanced chromosomal translocations with those carrying unbalanced chromosomal translocations using time-lapse microscopy.

METHODS

The study group included 270 embryos that underwent biopsies on day 3 for preimplantation genetic diagnosis (PGD) for chromosomal translocations in our unit between 2013 and 2015. All embryos were incubated under time-lapse microscopy and evaluated for timing of developmental events up to day 5. The timing of these events was compared between balanced and unbalanced embryos, potentially viable and nonviable variants, and maternal versus paternal inheritance of the translocation.

RESULTS

The PGD analysis found that 209 (77%) of the 270 biopsied embryos carried an unbalanced translocation. Embryos carrying unbalanced translocations, which are expected to lead to implantation failure or miscarriage, cleaved less synchronously and were delayed in time of cleavage to the 4-cell stage (t4) and in time of start of blastulation (tSB) compared with balanced embryos (P < 0.05). Furthermore, embryos carrying nonviable translocations demonstrated a significant delay at the time of pronuclei fading (tPNf) compared with those carrying potentially viable translocations (P < 0.05). Embryos whose unbalanced translocations were of maternal origin were significantly delayed in most of the morphokinetic parameters (including tPNf, t2, t3, t4, t6, t7, t8, cc2, s2, and tSB) compared with embryos carrying balanced translocations (P < 0.05).

CONCLUSIONS

Embryos carrying unbalanced chromosomal translocations mainly of maternal origin undergo delayed development and asynchronous cleavage that may lead to implantation failure or miscarriage.

Time-lapse algorithms and morphological selection of day-5 embryos for transfer: a preclinical validation study

OBJECTIVE

To determine the agreement between published time-lapse algorithms in selecting the best day-5 embryo for transfer, as well as the agreement between these algorithms and embryologists.

DESIGN

Prospective study.

SETTING

Private in vitro fertilization center.

PATIENT(S)

Four hundred and twenty-eight embryos from 100 cycles cultured in the EmbryoScope.

INTERVENTION(S)

None.

MAIN OUTCOME MEASURE(S)

Interalgorithm agreement as assessed by the Fleiss kappa coefficient.

RESULT(S)

Of seven published algorithms analyzed in this study, only one of the 18 possible pairs showed very good agreement (κ = 0.867); one pair showed good agreement (κ = 0.725), four pairs showed fair agreement (κ = 0.226-0.334), and the remaining 12 pairs showed poor agreement (κ = 0.008-0.149). Even in the best-case scenario, the majority of algorithms showed poor to moderate kappa scores (κ = 0.337-0.722) for the assessment of agreement between the embryo(s) selected as "best" by the algorithms and the embryo that was chosen by the majority (>5) of embryologists, as well as with the embryo that was actually selected in the laboratory on the day of transfer (κ = 0.315-0.802).

CONCLUSION(S)

The results of this study raise concerns as to whether the tested algorithms are applicable in different clinical settings, emphasizing the need for proper external validation before clinical use.

Selecting embryos with the highest implantation potential using data mining and decision tree based on classical embryo morphology and morphokinetics

PURPOSE

The objective of this work was to determine which embryonic morphokinetic parameters up to D3 of in vitro development have predictive value for implantation for the selection of embryos for transfer in clinical practice based upon information generated from embryo transfers with known implantation data (KID).

METHODS

A total of 800 KID embryos (100% implantation rate (IR) per transfer and 0% IR per transfer) cultured in an incubator with Time-Lapse system were retrospectively analysed. Of them, 140 embryos implanted, whereas 660 did not.

RESULTS

The analysis of morphokinetic parameters, together with the embryo morphology assessment on D3, enabled us to develop a hierarchical model that places the classical morphological score, the t4 and t8 morphokinetic values, as the variables with the best prognosis of implantation.

CONCLUSION

In our decision tree, the classical morphological score is the most predictive parameter. Among embryos with better morphological scores, morphokinetics permits deselection of embryos with the lowest implantation potential.

How much information about embryo implantation potential is included in morphokinetic data? A prediction model based on artificial neural networks and principal component analysis

PURPOSE

The aim of this study was to answer the question of how much information about embryo implantation potential can be obtained from morphokinetic parameters through the creation a predictive model based on morphokinetic information and using advanced data-mining and artificial intelligence methods.

MATERIALS AND METHODS

Time-lapse recordings of 610 embryos were included in the analysis. For each embryo, absolute (t₂, t₃, t₄, t₅) and relative (cc2 and s2) morphokinetic parameters were collected. Additionally, fragmentation levels assessed at t₂, t₃, t₄ and t₅ time-points, presence of multinucleation, evenness of blastomeres after the first and second division and women's age were included in the analysis.

RESULTS

The created predictive model of implantation was constructed on the basis of two advanced data-mining methods: principal component analysis (PCA) and artificial neural networks (ANN). The receiver operating characteristic (ROC) curve constructed for the created model demonstrated its good quality. The area under the ROC curve was AUC=0.75 with a 95% confidence interval (0.70, 0.80). Finally, the model was verified on a validation set and the results were also good, although slightly weaker: AUC=0.71, with a 95% confidence interval (0.59, 0.84).

CONCLUSIONS

The combination of two data-mining algorithms: PCA and ANN may be considered a method which can extract virtually all the available information from data. This methodology is indeed efficient, but models presented in the literature are also effective and close to the limit of the maximal information which can be extracted from morphokinetic data. The limit can be determined at the level of AUC value marginally above 0.7.

The impact of male age on embryo quality: a retrospective study using time-lapse imaging

OBJECTIVE

This study aimed to correlate male age with embryo morphokinetic parameters on D3 considering the timing and the exact moment of embryo cleavage.

METHODS

Time-lapse imaging was used to produce an ideal cleavage curve for the embryos analyzed. The percentage of embryos under the curve was analyzed and correlated with male age.

RESULTS

32.6% of the embryos from patients aged 28-33 years were under the curve; 36.2% of the embryos from patients aged 34-39 years were under the curve; 41.3% of the embryos from patients aged 40-45 years were under the curve; and 26.3% of the embryos fro patients aged 46-57 years were under the curve.

CONCLUSIONS

a statistically non-significant decrease was observed in the percentage of embryos under the optimal cleavage curve on D3 in the group of men aged between 40 and 45 years. Further studies looking into embryos in the blastocyst stage (D5 or D6) are required.

Development of a generally applicable morphokinetic algorithm capable of predicting the implantation potential of embryos transferred on Day 3

STUDY QUESTION

Can a generally applicable morphokinetic algorithm suitable for Day 3 transfers of time-lapse monitored embryos originating from different culture conditions and fertilization methods be developed for the purpose of supporting the embryologist's decision on which embryo to transfer back to the patient in assisted reproduction?

SUMMARY ANSWER

The algorithm presented here can be used independently of culture conditions and fertilization method and provides predictive power not surpassed by other published algorithms for ranking embryos according to their blastocyst formation potential.

WHAT IS KNOWN ALREADY

Generally applicable algorithms have so far been developed only for predicting blastocyst formation. A number of clinics have reported validated implantation prediction algorithms, which have been developed based on clinic-specific culture conditions and clinical environment. However, a generally applicable embryo evaluation algorithm based on actual implantation outcome has not yet been reported.

STUDY DESIGN, SIZE, DURATION

Retrospective evaluation of data extracted from a database of known implantation data (KID) originating from 3275 embryos transferred on Day 3 conducted in 24 clinics between 2009 and 2014. The data represented different culture conditions (reduced and ambient oxygen with various culture medium strategies) and fertilization methods (IVF, ICSI). The capability to predict blastocyst formation was evaluated on an independent set of morphokinetic data from 11 218 embryos which had been cultured to Day 5.

PARTICIPANTS/MATERIALS, SETTING, METHODS

The algorithm was developed by applying automated recursive partitioning to a large number of annotation types and derived equations, progressing to a five-fold cross-validation test of the complete data set and a validation test of different incubation conditions and fertilization methods. The results were expressed as receiver operating characteristics curves using the area under the curve (AUC) to establish the predictive strength of the algorithm.

MAIN RESULTS AND THE ROLE OF CHANCE

By applying the here developed algorithm (KIDScore), which was based on six annotations (the number of pronuclei equals 2 at the 1-cell stage, time from insemination to pronuclei fading at the 1-cell stage, time from insemination to the 2-cell stage, time from insemination to the 3-cell stage, time from insemination to the 5-cell stage and time from insemination to the 8-cell stage) and ranking the embryos in five groups, the implantation potential of the embryos was predicted with an AUC of 0.650. On Day 3 the KIDScore algorithm was capable of predicting blastocyst development with an AUC of 0.745 and blastocyst quality with an AUC of 0.679. In a comparison of blastocyst prediction including six other published algorithms and KIDScore, only KIDScore and one more algorithm surpassed an algorithm constructed on conventional Alpha/ESHRE consensus timings in terms of predictive power.

LIMITATIONS, REASONS FOR CAUTION

Some morphological assessments were not available and consequently three of the algorithms in the comparison were not used in full and may therefore have been put at a disadvantage. Algorithms based on implantation data from Day 3 embryo transfers require adjustments to be capable of predicting the implantation potential of Day 5 embryo transfers. The current study is restricted by its retrospective nature and absence of live birth information. Prospective Randomized Controlled Trials should be used in future studies to establish the value of time-lapse technology and morphokinetic evaluation.

WIDER IMPLICATIONS OF THE FINDINGS

Algorithms applicable to different culture conditions can be developed if based on large data sets of heterogeneous origin.

STUDY FUNDING/COMPETING INTEREST(S)

This study was funded by Vitrolife A/S, Denmark and Vitrolife AB, Sweden. B.M.P.’s company BMP Analytics is performing consultancy for Vitrolife A/S. M.B. is employed at Vitrolife A/S. M.M.’s company ilabcomm GmbH received honorarium for consultancy from Vitrolife AB. D.K.G. received research support from Vitrolife AB.

Assessment of human embryo development using morphological criteria in an era of time-lapse, algorithms and 'OMICS': is looking good still important?

With the worldwide move towards single embryo transfer there has been a renewed focus on the requirement for reliable means of assessing embryo viability. In an era of 'OMICS' technologies, and algorithms created through the use of time-lapse microscopy, the actual appearance of the human embryo as it progresses through each successive developmental stage to the blastocyst appears to have been somewhat neglected in recent years. Here we review the key features of the human preimplantation embryo and consider the relationship between morphological characteristics and developmental potential. Further, the impact of the culture environment on morphological traits, how key morphological qualities reflect aspects of embryo physiology, and how computer-assisted analysis of embryo morphology may facilitate a more quantitative approach to selection are discussed. The clinical introduction of time-lapse systems has reopened our eyes and given us a new vantage point from which to view the beauty of the initial stages of human life. Rather than a future in which the morphology of the embryo is deemed irrelevant, we propose that key features, such as multinucleation, cell size and blastocyst differentiation should be included in future iterations of selection/deselection algorithms.

Conventional morphology performs better than morphokinetics for prediction of live birth after day 2 transfer

Numerous studies have reported on the potential value of time-lapse variables for prediction of embryo viability. However, these variables have not been evaluated in combination with conventional morphological grading and patient characteristics. The aim of this study was to assess the ability of patient characteristics and embryo morphology together with morphokinetic variables to predict live birth after day 2 transfer. This retrospective analysis included 207 transferred embryos from 199 couples cultured in a time-lapse system up to day 2 of development. Good prediction of live birth or ranking of embryos with respect to live birth potential was achieved with early cleavage combined with fragmentation grade at 43-45 h. These variables were selected as the strongest predictors of live birth, as assessed by stepwise logistic regression, and additional inclusion of morphokinetic variables did not improve the model significantly. Also, neither logistic regression models nor classification tree models with morphokinetic variables were able to achieve equally good prediction of live birth, as measured by AUC on an external data set not used for model development. In conclusion, for fresh day 2 transfers early cleavage in combination with fragmentation grade at 43-45 h should be considered when selecting between good quality embryos.

The Presence of Endometrioma Does Not Impair Time-Lapse Morphokinetic Parameters and Quality of Embryos: A Study On Sibling Oocytes

OBJECTIVE

To see whether the oocytes retrieved from an ovary with an endometrioma would develop into embryos with aberrant timings of cleavage as assessed using time-lapse monitoring (TLM) and poorer morphologic quality compared with sibling oocytes from the contralateral ovary with no endometrioma in the same patient after intracytoplasmic sperm injection.

METHODS

This was an observational prospective study at an in vitro fertilization (IVF) center of a private hospital. It included analysis and comparison of 128 embryos (69 embryos developed from the ovary with endometrioma and 59 embryos from the contralateral ovary without endometrioma serving as controls from a total of 20 women with infertility). Morphology of the embryo was assessed twice (days 3 and 5), again by capturing images with the TLM system. Morphokinetic parameters of embryos and clinical pregnancy rates were recorded separately from ovaries with and without endometrioma and were the primary outcomes of the study. Secondary outcomes included number of retrieved oocytes, number of metaphase II (MII) oocytes, fertilization rates, and conventional morphological classification of embryos.

RESULTS

There were no differences in terms of the following time-lapse morphokinetic parameters of embryos. The mean numbers of oocytes and MII oocytes collected from the ovary with the endometrioma were similar to those collected from the contralateral ovary without endometrioma. Fertilization rates and the percentage of embryos with top morphologic quality were also similar.

CONCLUSIONS

According to the morphokinetic parameters, this study further strengthens the notion that removal of endometriomas before IVF is not a necessity in terms of better oocyte quality and development.

Do morphokinetic data sets inform pregnancy potential?

Purpose

The aim of this study was to create a model to predict the implantation of transferred embryos based on information contained in the morphokinetic parameters of time-lapse monitoring.

Methods

An analysis of time-lapse recordings of 410 embryos transferred in 343 cycles of in vitro fertilization (IVF) treatment was performed. The study was conducted between June 2012 and November 2014. For each embryo, the following data were collected: the duration of time from the intracytoplasmic sperm injection (ICSI) procedure to further division for two, three, four, and five blastomeres, time intervals between successive divisions, and the level of fragmentation assessed in successive time-points. Principal component analysis (PCA) and logistic regression were used to create a predictive model.

Results

Based on the results of principal component analysis and logistic regression analysis, a predictive equation was constructed. Statistically significant differences (p < 0.001) in the size of the created parameter between the implanted group (the median value: Me = −5.18 and quartiles: Q₁ = −5.61; Q₃ = −4.79) and the non-implanted group (Me = −5.69, Q₁ = −6.34; Q₃ = −5.16) were found. A receiver operating characteristic (ROC) curve constructed for the considered model showed the good quality of this predictive equation. The area under the ROC curve was AUC = 0.70 with a 95 % confidence interval (0.64, 0.75). The presented model has been validated on an independent data set, illustrating that the model is reliable and repeatable.

Conclusions

Morphokinetic parameters contain information useful in the process of creating pregnancy prediction models. However, embryo quality is not the only factor responsible for implantation, and, thus, the power of prediction of the considered model is not as high as in models for blastocyst formation. Nevertheless, as illustrated by the results of this study, the application of advanced data-mining methods in reproductive medicine allows one to create more accurate and useful models.

Morphokinetic analysis and embryonic prediction for blastocyst formation through an integrated time-lapse system

OBJECTIVE

To describe the events associated with the blastocyst formation and implantation that occur in embryos during preimplantation development based on the largest sample size ever described with time-lapse monitoring.

DESIGN

Observational, retrospective, single-center clinical study.

SETTING

University-affiliated private IVF center.

PATIENT(S)

A total of 7,483 zygotes from 990 first treatments of intracytoplasmic sperm injection (ICSI; 627 of oocyte donor vs. 363 autologous oocyte cycles), of which 832 blastocysts were transferred.

INTERVENTION(S)

No patient intervention. Embryos were cultured in a time-lapse monitoring system, and the embryos were transferred on day 5 after ICSI. Embryo selection was based on the multivariable model previously developed and on blastocyst morphology.

MAIN OUTCOME MEASURE(S)

Using a time-lapse system, embryo images were acquired every 15 minutes for 120 hours. Embryos cleavage time points up to the 9-cell stage (t2-t9) as well as to the morula stage (tM) and blastocyst formation (tB) were registered in hours after ICSI. Additionally, duration of the cell cycle and synchrony of the second and third cell cycles were defined. As a result, we have monitored the embryonic development of a total of 3,215 blastocysts, of which 832 were transferred. Finally, we analyzed the characteristics of embryonic development of blastocyst (phase 1) and of implanted and not implanted (phase 2) embryos as finally validated in an independent data set (phase 3).

RESULT(S)

A detailed retrospective analysis of cleavage times was made for 7,483 zygotes. We analyzed 17 parameters and found several significantly correlated with subsequent blastocyst formation and implantation. The most predictive parameters for blastocyst formation were time of morula formation, tM (81.28-96.0 hours after ICSI), and t8-t5 (≤8.78 hours) or time of transition of 5-blastomere embryos to 8-blastomere embryos with a receiver operating characteristic curve (ROC) value = 0.849 (95% confidence interval [CI], 0.835-0.854; phase 1). These parameters were less predictive of implantation, with a ROC value = 0.546 (95% CI, 0.507-0.585). We also observed that time for expansion blastocyst, tEB (107.9-112.9 hours after ICSI), and t8-t5 (≤5.67 hours after ICSI) predict blastocyst implantation, with a ROC value = 0.591 (95% CI, 0.552-0.630; phase 2). The model was validated on an independent data set and gave a ROC of 0.596 (0.526-0.666; phase 3).

CONCLUSION(S)

The inclusion of kinetic parameters into score evaluation may improve blastocyst selection criteria and can predict blastocyst formation with high accuracy. We propose two multivariable models based on our findings to classify embryos according to their probabilities of blastocyst stage and implantation in the largest data set ever reported of human blastocysts.

Relationship of polar bodies morphology to embryo quality and pregnancy outcome

The aim of this study was to explore whether the morphology of polar bodies (PBs) estimated at 16-18 h after insemination can be used as an additional marker for predicting human embryo quality or pregnancy outcome. The data from 355 patients who received standard in vitro fertilization (IVF) or intracytoplasmic sperm injection (ICSI) treatment after controlled ovarian hyperstimulation were recruited. Normal fertilized 3048 zygotes from 382 cycles were divided into two groups, PBs intact or fragmented, according to the morphology of PBs assessed at 16-18 h after insemination. Embryo quality and pregnancy outcome were compared between the two groups. It was shown that the day 3 (D3) good embryo rate, good quality blastocyst rate and available embryo rate of the PBs intact group were all significantly higher than that of the corresponding fragmented groups. However, no significant differences in pregnancy rate (PR) or implantation rate (IR) were observed between the intact and fragmented groups. Although PBs morphology estimated at 16-18 h after insemination had little effect on PR or IR in fresh embryo transfer cycles, a better embryo quality can be achieved in the PB-intact group, which is valuable for embryo selection.

Quality control and standardization of embryo morphology scoring and viability markers

A so-called 'good-quality embryo' may be defined as an embryo that has the potential to implant into the uterine endometrium and give rise to the birth of a healthy child. A standardized and objective scoring of embryo 'quality' is therefore crucial in the classification and selection of embryos. However, embryo scoring is still being performed mainly via ocular evaluation, which often results in different interpretations of embryo quality. The addition of viability markers, such as measuring gene expression or the uptake/release of metabolites, proteins or RNA/DNA molecules in the culture media, would increase the possibility of standardized measurements. However, no single biomarker has yet been introduced into standard clinical practice, mainly due to the complexity of the techniques and the influence of biological variations and differences in culture conditions. In this paper different methods for the scoring of embryos and the possibility of standardizing and implementing quality control systems are discussed.