Correlation between aneuploidy, standard morphology evaluation and morphokinetic development in 1730 biopsied blastocysts: a consecutive case series study

STUDY QUESTION

Are there correlations among human blastocyst ploidy status, standard morphology evaluation and time-lapse kinetics?

SUMMARY ANSWER

Correlations were observed, in that euploid human blastocysts showed a higher percentage with top quality inner cell mass (ICM) and trophectoderm (TE), higher expansion grades and shorter time to start of blastulation, expansion and hatching, compared to aneuploid ones.

WHAT IS KNOWN ALREADY

Embryo quality has always been considered an important predictor of successful implantation and pregnancy. Nevertheless, knowledge of the relative impact of each morphological parameter at the blastocyst stage needs to be increased. Recently, with the introduction of time-lapse technology, morphokinetic parameters can also be evaluated. However, a large number of studies has reported conflicting outcomes.

STUDY DESIGN, SIZE, DURATION

This was a consecutive case series study. The morphology of 1730 blastocysts obtained in 530 PGS cycles performed from September 2012 to April 2014 that underwent TE biopsy and array comparative genomic hybridization was analyzed retrospectively. A total of 928 blastocysts were cultured in a time-lapse incubator allowing morphokinetic parameters to be analyzed.

PARTCIPANTS/MATERIALS, SETTING, METHOD

Mean female age was 36.8 ± 4.24 years. Four hunderd fifty-four couples were enrolled in the study: 384, 64 and 6 of them performed single, double or triple PGS cycles, respectively. In standard morphology evaluation, the expansion grade, and quality of the ICM and TE were analyzed. The morphokinetic parameters observed were second polar body extrusion, appearance of two pronuclei, pronuclear fading, onset of two- to eight-cell divisions, time between the two- and three-cell (cc2) and three- and four-cell (s2) stages, morulae formation time, starting blastulation, full blastocyst stage, expansion and hatching timing.

MAIN RESULTS AND THE ROLE OF CHANCE

Of the 1730 biopsied blastocysts, 603 were euploid and 1127 aneuploid. We observed that 47.2% of euploid and 32.8% of aneuploid blastocysts showed top quality ICM (P < 0.001), and 17.1% of euploid and 28.5% of aneuploid blastocysts showed poor quality ICM (P < 0.001). Top quality TE was present in 46.5% of euploid and 31.1% of aneuploid blastocysts (P < 0.001), while 26.6% of euploid and 38.1% of aneuploid blastocysts showed poor quality TE (P < 0.001). Regarding expansion grade, 81.1% of euploid and 72.4% of aneuploid blastocysts were fully expanded (Grade 5-6; P < 0.001). The timing of cleavage from the three- to four-cell stage, of reaching four-cell stage, of starting blastulation, reaching full blastocyst stage, blastocyst expansion and hatching were 2.6 (95% confidence interval (CI): 1.7-3.5), 40.0 (95% CI: 39.3-40.6), 103.4 (95% CI: 102.2-104.6), 110.2 (95% CI: 108.8-111.5), 118.7 (95% CI: 117.0-120.5) and 133.2 (95% CI: 131.2-135.2) hours in euploid blastocysts, and 4.2 (95% CI: 3.6-4.8), 41.1 (95% CI: 40.6-41.6), 105.0 (95% CI: 104.0-106.0), 112.8 (95% CI: 111.7-113.9), 122.1 (95% CI: 120.7-123.4) and 137.4 (95% CI: 135.7-139.1) hours in aneuploid blastocysts (P < 0.05 for early and P < 0.0001 for later stages of development), respectively. No statistically significant differences were found between euploid and aneuploid blastocysts for the remaining morphokinetic parameters.A total of 407 embryo transfers were performed (155 fresh, 252 frozen-thawed blastocysts). Higher clinical pregnancy, implantation and live birth rates were obtained in frozen-thawed compared to fresh embryo transfers (P = 0.0104, 0.0091 and 0.0148, respectively). The miscarriage rate was 16.1% and 19.6% in cryopreserved and fresh embryo transfer, respectively. The mean female age was lower in the euploid compared to aneuploid groups (35.0 ± 3.78 versus 36.7 ± 4.13 years, respectively), We found an increasing probability for aneuploidy with female age of 10% per year (odds ratio (OR) = 1.1, 95% CI: 1.1-1.2, P < 0.001).

LIMITATIONS, REASONS FOR CAUTION

The main limitation of morphology assessment is that it is a static system and can be operator-dependent. In this study, eight embryologists performed morphology assessments. The main limitation of the time-lapse technology is that it is impossible to rotate the embryos making it very difficult to observe them in case of blastomere overlapping or increased cytoplasmic fragmentation.

WIDER IMPLICATIONS OF THE FINDINGS

Although there seems to be a relationship between the ploidy status and blastocyst morphology/development dynamics, the evaluation of morphological and morphokinetic parameters cannot currently be improved upon, and therefore replace, PGS. Our results on ongoing pregnancy and miscarriage rates suggest that embryo evaluation by PGS or time-lapse imaging may not improve IVF outcome. However, time-lapse monitoring could be used in conjunction with PGS to choose, within a cohort, the blastocysts to analyze or, when more than one euploid blastocyst is available, to select which one should be transferred.

STUDY FUNDING/COMPETING INTERESTS

No specific funding was obtained for this study. None of the authors have any competing interests to declare.

Different effectiveness of closed embryo culture system with time-lapse imaging (EmbryoScope(TM)) in comparison to standard manual embryology in good and poor prognosis patients: a prospectively randomized pilot study

BACKGROUND

Previously manual human embryology in many in vitro fertilization (IVF) centers is rapidly being replaced by closed embryo incubation systems with time-lapse imaging. Whether such systems perform comparably to manual embryology in different IVF patient populations has, however, never before been investigated. We, therefore, prospectively compared embryo quality following closed system culture with time-lapse photography (EmbryoScope™) and standard embryology. We performed a two-part prospectively randomized study in IVF (clinical trial # NCT92256309). Part A involved 31 infertile poor prognosis patients prospectively randomized to EmbryoScope™ and standard embryology. Part B involved embryos from 17 egg donor-recipient cycles resulting in large egg/embryo numbers, thus permitting prospectively alternative embryo assignments to EmbryoScope™ and standard embryology. We then compared pregnancy rates and embryo quality on day-3 after fertilization and embryologist time utilized per processed embryo.

RESULTS

Part A revealed in poor prognosis patients no differences in day-3 embryo scores, implantation and clinical pregnancy rates between EmbryoScope™ and standard embryology. The EmbryoScope™, however, more than doubled embryology staff time (P < 0.0001). In Part B, embryos grown in the EmbyoScope™ demonstrated significantly poorer day-3 quality (depending on embryo parameter between P = 0.005 and P = 0.01). Suspicion that conical culture dishes of the EmbryoScope™ (EmbryoSlide™) may be the cause was disproven when standard culture dishes demonstrated no outcome difference in standard incubation.

CONCLUSIONS

Though due to small patient numbers preliminary, this study raises concerns about the mostly uncontrolled introduction of closed incubation systems with time lapse imaging into routine clinical embryology. Appropriately designed and powered prospectively randomized studies appear urgently needed in well-defined patient populations before the uncontrolled utilization of these instruments further expands.

TRIAL REGISTRATION

NCT02246309 Registered September 18, 2014.

Live birth rate and number of blastomeres on day 2 transfer

PURPOSE

To investigate whether the presence of large fragment (LF) and abnormal cell divisions (ACDs) has influenced the correlation between live birth rate and number of blastomeres detected on day 2 by conventional scoring.

METHODS

This study included 578 embryos cultured in time lapse and selected for transfer by conventional scoring on day 2. By time-lapse recordings, embryos were reassessed to identify ACDs and/or LFs mistaken as blastomeres. The latter identifications were used to recalculate fragmentation rate and the number of blastomeres. Life birth rate according to number of blastomeres was compared in (a) embryos selected by conventional scoring and (b) embryos reassessed by time lapse.

RESULTS

After conventional scoring, embryos with four cells had a significantly higher pregnancy rate than embryos with less than four cells and embryos with more than four cells. By time-lapse assessment, ACDs and/or recalculated fragmentation >25 % was recognized in 106/578 (18.3 %) of transferred embryos. None of them resulted in a live birth. After exclusion of these embryos, the number of blastomeres on the day of transfer did not have any impact on life birth rate.

CONCLUSION

Conventional scoring on day 2 did not detect ACDs and LFs mistaken as blastomeres. LFs can lead to a recalculated fragmentation rate to >25 %. No significant correlation between live birth rate and number of blastomeres in day 2 embryos was observed when embryos with ACDs and fragmentation >25 % were excluded. Recognition of ACDs and fragmentation >25 % is more predictive of live birth than number of blastomeres.

Time-lapse variables and embryo gender: a retrospective analysis of 81 live births obtained following minimal stimulation and single embryo transfer

PURPOSE

The purpose of this study was to determine which morphokinetic variables are related to embryo gender in a cohort of consecutive live births obtained through single blastocyst transfer following mild ovarian stimulation.

METHODS

Eighty-one live births (49 % of them females) from successfully treated, consecutive infertile patients (maternal age 36.9 ± 3.8 years, range 28-46) who underwent minimal ovarian stimulation, prolonged embryo culture in a time-lapse monitoring (TLM) incubator and elective single blastocyst transfers during 2012-2014. Early (PNf, t2-t9, cc2a, b, s2, s3) and late (tM, tSB, tfullB, texpB1, and texpB2) morphokinetic variables were scored according to published consensus criteria and were normalized to the time of pronuclear fading. For each variable, the ranges with the highest proportion of female embryos (optimal range) were determined by detailed examination of histograms.

RESULTS

Female embryo gender was associated both with late cleavage (t8), morula (tM), and blastocyst stage morphokinetic variables. The strongest associations (adjusted ORs, 7.0-7.8) were found for late, expanded stage blastocyst parameters; tfullB, texpB1, and texpB2. The proportion of female embryos was 69-71 and 25-26 % inside and outside of the optimal ranges, respectively. This allowed to predict 74-78 % of them, increasing their proportion by 57 % compared to the average.

CONCLUSIONS

Although the sample size of our cohort was limited, our findings suggest that several expanded blastocyst stage morphokinetic parameters are associated with female embryo gender. If confirmed on a larger sample these could be potentially used to increase the proportion of female embryos among non-invasively selected blastocysts following single embryo transfer.

Morphokinetic Evaluation of Embryo Development in a Mouse Model: Functional and Molecular Correlates

Although time-lapse analysis of early embryo cleavage parameters (morphokinetics) predicts blastocyst development, it has not been definitively linked to establishing pregnancy and live birth. For example, a direct comparison of the developmental potential of embryos with optimal kinetic parameters compared to suboptimal kinetics has not been performed with human embryos. To ascertain whether such a linkage exists, we developed a mouse model of morphokinetic analysis of early embryo cleavage using time-lapse microscopy to predict blastocyst formation and tested whether cleavage parameters predict pregnancy outcome by transferring morphokinetically optimal and suboptimal embryos into a single host. Using classification and regression trees, we established that the timing of the second and third mitotic divisions (division from two to three and three to four cells, respectively) predicts blastocyst development in the mouse. Using this prediction model, we found that the incidence of sustained implantation at mid-gestation was significantly higher for the optimal compared to suboptimal embryos. In addition, the incidence of resorption among implanted embryos was significantly higher in the suboptimal compared to the optimal group. Transcript profiling of optimal and suboptimal embryos revealed minimal differences between the two groups, suggesting that time-lapse imaging of early embryo cleavage events provides additional information regarding developmental competence apart from gene expression.

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.

Chromosomal instability in mammalian pre-implantation embryos: potential causes, detection methods, and clinical consequences

Formation of a totipotent blastocyst capable of implantation is one of the first major milestones in early mammalian embryogenesis, but less than half of in vitro fertilized embryos from most mammals will progress to this stage of development. Whole chromosomal abnormalities, or aneuploidy, are key determinants of whether human embryos will arrest or reach the blastocyst stage. Depending on the type of chromosomal abnormality, however, certain embryos still form blastocysts and may be morphologically indistinguishable from chromosomally normal embryos. Despite the implementation of pre-implantation genetic screening and other advanced in vitro fertilization (IVF) techniques, the identification of aneuploid embryos remains complicated by high rates of mosaicism, atypical cell division, cellular fragmentation, sub-chromosomal instability, and micro-/multi-nucleation. Moreover, several of these processes occur in vivo following natural human conception, suggesting that they are not simply a consequence of culture conditions. Recent technological achievements in genetic, epigenetic, chromosomal, and non-invasive imaging have provided additional embryo assessment approaches, particularly at the single-cell level, and clinical trials investigating their efficacy are continuing to emerge. In this review, we summarize the potential mechanisms by which aneuploidy may arise, the various detection methods, and the technical advances (such as time-lapse imaging, "-omic" profiling, and next-generation sequencing) that have assisted in obtaining this data. We also discuss the possibility of aneuploidy resolution in embryos via various corrective mechanisms, including multi-polar divisions, fragment resorption, endoreduplication, and blastomere exclusion, and conclude by examining the potential implications of these findings for IVF success and human fecundity.

Myoinositol Improves Embryo Development in PCOS Patients Undergoing ICSI

The aim of this study was to investigate the activity of myoinositol, in a court of 217 PCOS women undergoing intracytoplasmic sperm injection (ICSI), on pregnancy rate, embryo development, estradiol, and progesterone concentration in blood serum, superoxide dismutase (SOD), and catalase (CAT) in follicular fluid. Concerning the court of patient, 112 (groups I and II) out of 217 were PCOS women, whereas group III consisted of healthy subjects (not PCOS). Group I patients were treated with 400 μg of folic acid per day for 3 months before ICSI, whereas group II patients received 4000 mg of myoinositol and 400 μg of folic acid per day for 3 months before ICSI. Group II revealed a shorter embryo/blastocyst development period between microinjection and 5-cell stage compared to group I. The difference in SOD concentration between groups I and II and between groups II and III was statistically significant. In group II, 34.62% of pregnancies were obtained, whereas in group I this number reached 20% (NS). Myoinositol increased embryo development dynamics and accelerated blastocyst stage reaching time; however, no effect was shown on clinical pregnancy. Furthermore, it restored SOD concentration, lowered in PCOS women, but did not exert any effect on CAT concentration.

Ovarian stimulation with human and recombinant gonadotropin - comparison of in vitro fertilization efficiency with use of time-lapse monitoring

Background

Achieving pregnancy by in vitro fertilization (IVF) treatment depends on many factors, including the ovaries’ capacity and the efficiency of ovarian stimulation. The aim of this study was to assess the influence of ovarian stimulation with human and recombinant gonadotropin, as well as specific hormonal parameters, on the effectiveness of IVF and the dynamics of embryonic development.

Methods

The study involved 221 women aged 25–35 years in whom intracytoplasmic sperm injection was performed. The ovarian stimulation was carried out according to the short protocol: injections of gonadotropin-releasing hormone analogue were followed by human (hFSH) and recombinant (rFSH) follicle-stimulating hormone administration. The growth of embryos was monitored with a time-lapse system. Levels of follicle-stimulating hormone (FSH), luteinizing hormone (LH), and anti-Müllerian hormone (AMH) were measured before ovarian stimulation, and levels of estradiol were assessed on the day of administration of recombinant chorionic gonadotropin.

Results

Pregnancy was achieved in 77 women (group A) – 42 (54.55 %) of them were stimulated with hFSH and 35 (45.45 %) were stimulated with rFSH. Among the 144 women in whom pregnancy was not achieved (group B), hFSH was administered to 73 (50.69 %) women and rFSH to 71 (49.31 %) women. In both groups subsequent embryo development stages were usually noted earlier after hFSH stimulation than after rFSH stimulation. The average values of AMH, estradiol, and estradiol per >17 mm follicle were higher in group A; in turn, FSH and LH mean levels were higher in group B. ROC curve analysis showed no statistically significant differences between accuracy of using FSH and AMH levels to predict pregnancy after IVF.

Conclusions

The kind of gonadotropin applied to stimulate ovaries impacts the dynamics of embryo development - in women stimulated with hFSH, subsequent development stages were usually observed earlier than in women treated with rFSH; however, there was no statistically significant difference in pregnancy rates between women who were hFSH stimulated and those who were rFSH stimulated. The mean estradiol level was higher in women who achieved pregnancy than in women in whom pregnancy was not achieved AMH and FSH have the greater impact on achieving pregnancy than other hormones, and the value of AMH and FSH in predicting pregnancy is similar.

Timing of human preimplantation embryonic development is confounded by embryo origin

STUDY QUESTION

To what extent do patient- and treatment-related factors explain the variation in morphokinetic parameters proposed as embryo viability markers?

SUMMARY ANSWER

Up to 31% of the observed variation in timing of embryo development can be explained by embryo origin, but no single factor elicits a systematic influence.

WHAT IS KNOWN ALREADY

Several studies report that culture conditions, patient characteristics and treatment influence timing of embryo development, which have promoted the perception that each clinic must develop individual models. Most of the studies have, however, treated embryos from one patient as independent observations, and only very few studies that evaluate the influence from patient- and treatment-related factors on timing of development or time-lapse parameters as predictors of viability have controlled for confounding, which implies a high risk of overestimating the statistical significance of potential correlations.

STUDY DESIGN, SIZE, DURATION

Infertile patients were prospectively recruited to a cohort study at a hospital fertility clinic from February 2011 to May 2013. Patients aged <38 years without endometriosis were eligible if ≥8 oocytes were retrieved. Patients were included only once. All embryos were monitored for 6 days in a time-lapse incubator.

PARTICIPANTS/MATERIALS, SETTING, METHODS

A total of 1507 embryos from 243 patients were included. The influence of fertilization method, BMI, maternal age, FSH dose and number of previous cycles on timing of t2-t5, duration of the 2- and 3-cell stage, and development of a blastocoel (tEB) and full blastocoel (tFB) was tested in multivariate, multilevel linear regression analysis. Predictive parameters for live birth were tested in a logistic regression analysis for 223 single transferred blastocysts, where time-lapse parameters were investigated along with patient and embryo characteristics.

MAIN RESULTS AND THE ROLE OF CHANCE

Moderate intra-class correlation coefficients (0.16-0.31) were observed for all parameters except duration of the 3-cell stage, which demonstrates that embryos from one patient elicit clustering at a patient level. No single patient- and treatment-related factor was found to systematically influence the timing from cleavage to blastocyst stage, which indicates that no individual patient-related factor can be identified that separately explains the clustering throughout the entire developmental stages. The blastocyst parameters were more affected by patient-related factors than cleavage stage parameters, as tEB occurred significantly later with older age (0.29 h/year (95% confidence interval: CI 0.03; 0.56)), while both tEB and tFB occurred significantly later with increasing dose of FSH (tEB: 0.12 h/100 IU FSH (95% CI 0.01;0.24); tFB 0.14 h/100 IU FSH (95% CI 0.03;0.27)) and with more previous attempts (tEB: 1.2 h/attempt (95% CI 0.01;2.5); tFB 1.4 h/attempt (0.10;2.7)). Fertilization method affected timing of the first division, with ICSI embryos cleaving significantly faster than IVF embryos (-3.6% (95% CI -6.4; -0.77)), whereas no difference was found in the subsequent divisions. The univariable regression analysis identified female age, cumulative FSH dose, degree of blastocyst expansion, score of the inner cell mass and timing of full blastocyst formation as predictors of live birth. The timing of full blastocyst formation (tFB) did not remain significant when adjusting for age, number of previous cycles and cumulative FSH dose, which were the parameters shown to influence tFB in the mixed regression model.

LIMITATIONS, REASONS FOR CAUTION

Only good prognosis patients were enrolled, so these results may not be generalized to all infertile women. Not all patient-related factors were investigated.

WIDER IMPLICATIONS OF THE FINDINGS

Our findings underline the importance of treating embryos as dependent observations and suggest a high risk of patient-based confounding in retrospective studies. The impact of confounders and the embryo origin needs to be addressed in order to apply appropriate statistical models in observational studies. Furthermore, this observation emphasizes the need for RCTs for evaluating use of time-lapse parameters for embryo selection.

STUDY FUNDING/COMPETING INTERESTS

Funding for the cohort study was provided by the Lippert Foundation, the Toyota Foundation, the Aase og Einar Danielsen foundation and NordicInfu Care research grant. Research at the Fertility Clinic, Aarhus University Hospital is supported by an unrestricted grant from MSD and Ferring. K.K. is funded by a grant from the Danish Council for Independent Research Medical Sciences. The authors declare no competing interest.

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.

Mammalian pre-implantation chromosomal instability: species comparison, evolutionary considerations, and pathological correlations

Pre-implantation embryo development in mammals begins at fertilization with the migration and fusion of the maternal and paternal pro-nuclei, followed by the degradation of inherited factors involved in germ cell specification and the activation of embryonic genes required for subsequent cell divisions, compaction, and blastulation. The majority of studies on early embryogenesis have been conducted in the mouse or non-mammalian species, often requiring extrapolation of the findings to human development. Given both conserved similarities and species-specific differences, however, even comparison between closely related mammalian species may be challenging as certain aspects, including susceptibility to chromosomal aberrations, varies considerably across mammals. Moreover, most human embryo studies are limited to patient samples obtained from in vitro fertilization (IVF) clinics and donated for research, which are generally of poorer quality and produced with germ cells that may be sub-optimal. Recent technical advances in genetic, epigenetic, chromosomal, and time-lapse imaging analyses of high quality whole human embryos have greatly improved our understanding of early human embryogenesis, particularly at the single embryo and cell level. This review summarizes the major characteristics of mammalian pre-implantation development from a chromosomal perspective, in addition to discussing the technological achievements that have recently been developed to obtain this data. We also discuss potential translation to clinical applications in reproductive medicine and conclude by examining the broader implications of these findings for the evolution of mammalian species and cancer pathology in somatic cells.

The impact of paternal factors on cleavage stage and blastocyst development analyzed by time-lapse imaging-a retrospective observational study

PURPOSE

Various time-lapse studies have postulated embryo selection criteria based on early morphokinetic markers. However, late paternal effects are mostly not visible before embryonic genome activation. The primary objective of this retrospective study was to investigate whether those early morphokinetic algorithms investigated by time-lapse imaging are reliable enough to allow for the accurate selection of those embryos that develop into blastocysts, while of course taking into account the correlation with the type of injected spermatozoa.

METHODS

During a period of 18 months, a total of 461 MII oocytes from 43 couples with severe male factor infertility and previous "external" IVF failures after cleavage-stage embryo transfer (ET) were fertilized by intracytoplasmic morphologically selected sperm injection (IMSI). Thereof, 373 embryos were monitored in a time-lapse incubator until ET on day 5. Blastocyst outcome in combination with three previously postulated MKc (cc2: t3-t2, 5-12 h; t3, 35-40 h; t5, 48-56 h) and the morphology of the selected sperm were analyzed.

RESULTS

A significant increase in the rate of blastocysts (54.0 vs. 36.3 %; P < 0.01) and top blastocysts (25.3 vs. 10.8 %; P < 0.001) was observed in the group of those meeting all three morphokinetic criteria (MKc3). However, MKc3 were only met in 23.3 % of all embryos. Moreover, TBR was influenced by the type of injected spermatozoa. In both groups, TBR decreased dramatically (MKc3, 35.0 vs. 17.0 %; MKc < 3, 14.2 vs. 8.4 %) when class II/III sperm instead of class I were injected.

CONCLUSION

Early morphokinetic parameters might give some predictive information but fail to serve as a feasible selective tool for the prediction of blastocyst development given the influence of the type of spermatozoa injected.

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.

Morphokinetic parameters using time-lapse technology and day 5 embryo quality: a prospective cohort study

PURPOSE

The aims of this prospective study were to evaluate whether time-lapse parameters can aid in the prediction of day 5 embryo quality and also to assess their discriminatory capacity.

METHODS

In this prospective cohort study, we used time-lapse technology to record specific timings of key events for 380 day 5 blastocysts (originating from 108 patients). Generalized estimating equation regression models were used to evaluate the capacity of these markers to identify a top-quality blastocyst. Multivariable regression models were also constructed, aiming to identify the model with the highest capacity to predict a top-quality blastocyst. The discriminatory capacity of single predictors or composite models was assessed with the use of receiver operating characteristic (ROC) analyses.

RESULTS

Eight significant predictive parameters of a top-quality blastocyst were identified: s3, t6, t7, t8, tM, tSB, tB and tEB. A ROC analysis of the identified parameters found s3 (area under the curve--AUC 0.585, 95 % CI 0.534-0.635) to have the best individual discriminatory capacity to predict a top-quality blastocyst prior to embryo compaction. The parameter tEB (AUC 0.727, 95 % CI 0.675-0.775) was the best predictor regardless of embryo stage. A model containing s3, t8 and tEB showed a slightly increased discriminatory capacity for top-quality blastocyst prediction (AUC 0.748, 95 % CI 0.697-0.794).

CONCLUSIONS

The identified morphokinetic parameters and their cutoffs, albeit of limited clinical value, add to the increasing knowledge concerning the potential predictive markers of a top-quality blastocyst. Additional evidence is necessary before validated time-lapse parameters can be used for embryo selection in IVF laboratories.

A critical appraisal of time-lapse imaging for embryo selection: where are we and where do we need to go?

PURPOSE

The aim of this study was to undertake a critical appraisal of the available evidence for the use of time-lapse imaging for embryo selection in clinical IVF.

METHODS

A literature search in PubMed, Scopus, Cochrane Central, ClinicalTrials.gov, Current Controlled Trials, and WHO International Clinical Trials Registry Platform was performed to identify randomized controlled trials that investigated the effect of time-lapse embryo selection and/or the time-lapse incubation system on ongoing pregnancy rate. We then performed a systematic review and assessed the relative risks (RRs) and 95 % confidence intervals (CIs) for ongoing pregnancy rates and the risk of bias of the eligible studies.

RESULTS

We identified four eligible randomized studies, three of which investigated the effect of both time-lapse incubation system and selection on ongoing pregnancy rate; the pooled result revealed a benefit of this intervention (relative risk (RR) 1.20; 95 % CI 1.05-1.37). However, the evidence was judged to be of low quality due to study limitations; a beneficial effect was observed in only one study deemed to be at high risk of bias. The single study assessing the effect of only the time-lapse incubation system revealed a non-significant negative effect (RR 0.71; 95 % CI 0.49-1.03).

CONCLUSIONS

The findings from this systematic review of the current evidence do not support routine use of time-lapse technology in clinical IVF. We therefore believe that the use of time-lapse imaging for embryo selection should remain experimental and that couples should not be subject to a surcharge for having their embryos cultured in a time-lapse imaging system. Future studies evaluating this technology in well-designed trials should be performed.

Distinct differences in global gene expression profiles in non-implanted blastocysts and blastocysts resulting in live birth

Results from animal models points towards the existence of a gene expression profile that is distinguishably different in viable embryos compared with non-viable embryos. Knowledge of human embryo transcripts is however limited, in particular with regard to how gene expression is related to clinical outcome. The purpose of the present study was therefore to determine the global gene expression profiles of human blastocysts. Next Generation Sequencing was used to identify genes that were differentially expressed in non-implanted embryos and embryos resulting in live birth. Three trophectoderm biopsies were obtained from morphologically high quality blastocysts resulting in live birth and three biopsies were obtained from non-implanting blastocysts of a comparable morphology. Total RNA was extracted from all samples followed by complete transcriptome sequencing. Using a set of filtering criteria, we obtained a list of 181 genes that were differentially expressed between trophectoderm biopsies from embryos resulting in either live birth or no implantation (negative hCG), respectively. We found that 37 of the 181 genes displayed significantly differential expression (p<0.05), e.g. EFNB1, CYTL1 and TEX26 and TESK1, MSL1 and EVI5 in trophectoderm biopsies associated with live birth and non-implanting, respectively. Out of the 181 genes, almost 80% (145 genes) were up-regulated in biopsies from un-implanted embryos, whereas only 20% (36 genes) showed an up-regulation in the samples from embryos resulting in live birth. Our findings suggest the presence of molecular differences visually undetectable between implanted and non-implanted embryos, and represent a proof of principle study.

Assessing embryo quality by combining non-invasive markers: early time-lapse parameters reflect gene expression in associated cumulus cells

STUDY QUESTION

Are there associations between early time-lapse parameters, expression of candidate embryo viability genes in cumulus cells and embryo quality on Day 5?

SUMMARY ANSWER

Early time-lapse parameters correlate to the expression levels of candidate embryo viability genes in cumulus cells but a combined analysis including both time-lapse and candidate gene expression did not identify significant predictors of embryo quality on Day 5.

WHAT IS KNOWN ALREADY

Recent evidence suggests that early time-lapse parameters are predictive of blastocyst development. Similarly, a number of candidate genes in cumulus cells have been identified as potential markers of embryo viability. Relationships between time-lapse parameters and candidate gene expression in cumulus cells have not been investigated, and a combined analysis of these markers has not been attempted in relation to embryo quality.

STUDY DESIGN, SIZE, DURATION

A total of 78 embryos obtained by ICSI from 22 patients were studied by time-lapse and measurement of cumulus cell gene expression of known markers of embryo viability. Time-lapse and cumulus cell gene expression data were assessed in relation to embryo quality on Day 5.

PARTICIPANTS/MATERIALS, SETTING, METHODS

All women, aged 32-40 years, underwent ICSI treatment for male infertility. Embryos with annotatable time to pronuclear breakdown (tPNB), division to two cells (t2C), three cells (t3C), four cells (t4C) and five cells (t5C) were included in the study. Expression levels of 27 candidate genes for embryo viability were measured in 78 associated cumulus cell masses using quantitative real-time PCR.

MAIN RESULTS AND THE ROLE OF CHANCE

Cumulus cell expression of 11 candidate genes involved in energy metabolism (ATPase, H+ transporting, lysosomal 70 kDa, V1 subunit A (ATP6V1A), NADH dehydrogenase (ubiquinone) 1 alpha subcomplex, 1, 7.5 kDa (NDUFA1), lactate dehydrogenase A (LDHA), phosphofructokinase platelet (PFKP) and solute carrier family 2 member 4 (SLC2A4), mitochondrial biogenesis (DNA directed RNA polymerase, mitochondrial (POLRMT) and transcription factor A, mitochondrial (TFAM), signalling (prostaglandin-endoperoxide synthase 2), steroidogenesis (cytochrome P450, family 11, subfamily A, polypeptide 1 (CYP11A1) and cell stress (heat shock 70 kDa protein 5 (HSPA5) and peroxiredoxin 3 (PRDX3)) correlated to time-lapse parameters of the developing embryo, largely for t3C onwards (all P < 0.05). Expression of ATP synthase, H+ transporting, mitochondrial Fo complex, subunit E (ATP51), HSPA5, PFKP, PRDX3 and versican (VCAN) and the parameter t4C were also related to embryo quality on Day 5 (all P < 0.05). Ordinal logistic regression, where gene expression and time-lapse parameters were combined, did not identify any significant predictors of embryo quality on Day 5.

LIMITATIONS AND REASON FOR CAUTION

Data are from a preliminary study, limited by a small sample size and using more than one ovarian stimulation protocol. A possible limitation is that each follicle was treated as an independent observation, although a considerable fraction of embryos were from the same patient.

WIDER IMPLICATIONS OF THE FINDINGS

Results presented in this study suggest that some of the variation of time-lapse parameters may be related to cumulus cell gene expression and thus the ovarian microenvironment in which the oocyte developed. Although the current study did not identify significant predictors of embryo quality on Day 5, investigation in a larger cohort may determine whether cumulus cell gene expression and time-lapse parameters can be combined to predict embryo quality.

STUDY FUNDING/COMPETING INTERESTS

Funding was provided by Fertility Associates Ltd, the Auckland Medical Research Foundation and the University of Auckland. J.C.P. has a 0.5% shareholding in Fertility Associates. All other authors of this manuscript have nothing to declare and no conflict of interest that could be perceived as prejudicing the impartiality of the research reported.

Unaltered timing of embryo development in women with polycystic ovarian syndrome (PCOS): a time-lapse study

PURPOSE

Polycystic ovarian syndrome (PCOS) is a common cause of female infertility. Factors other than anovulation, such as low embryo quality have been suggested to contribute to the infertility in these women. This 2-year retrospective study used timelapse technology to investigate the PCOS-influence on timing of development in the pre-implantation embryo (primary endpoint). The secondary outcome measure was live birth rates after elective single-embryo transfer.

METHODS

In total, 313 embryos from 43 PCOS women, and 1075 embryos from 174 non-PCOS women undergoing assisted reproduction were included. All embryos were monitored until day 6. Differences in embryo kinetics were tested in a covariance regression model to account for potential confounding variables: female age, BMI, fertilization method and male infertility.

RESULTS

Time to initiate compaction and reach the morula stage as well as the duration of the 4th cleavage division was significantly shorter in PCOS embryos compared with non-PCOS embryos. No other kinetic differences were found at any time-points annotated. The proportion of multi-nucleated cells at the 2-cell stage was significantly higher in PCOS embryos compared with non-PCOS embryos. The live birth rates were comparable between the two groups.

CONCLUSION

The findings suggest that the causative factor for subfertility in PCOS is not related to timing of development in the pre-implantation embryo.

Microwells support high-resolution time-lapse imaging and development of preimplanted mouse embryos

A vital aspect affecting the success rate of in vitro fertilization is the culture environment of the embryo. However, what is not yet comprehensively understood is the affect the biochemical, physical, and genetic requirements have over the dynamic development of human or mouse preimplantation embryos. The conventional microdrop technique often cultures embryos in groups, which limits the investigation of the microenvironment of embryos. We report an open microwell platform, which enables micropipette manipulation and culture of embryos in defined sub-microliter volumes without valves. The fluidic environment of each microwell is secluded from others by layering oil on top, allowing for non-invasive, high-resolution time-lapse microscopy, and data collection from each individual embryo without confounding factors. We have successfully cultured mouse embryos from the two-cell stage to completely hatched blastocysts inside microwells with an 89% success rate (n = 64), which is comparable to the success rate of the contemporary practice. Development timings of mouse embryos that developed into blastocysts are statistically different to those of embryos that failed to form blastocysts (p-value < 10(-10), two-tailed Student's t-test) and are robust indicators of the competence of the embryo to form a blastocyst in vitro with 94% sensitivity and 100% specificity. Embryos at the cleavage- or blastocyst-stage following the normal development timings were selected and transferred to the uteri of surrogate female mice. Fifteen of twenty-two (68%) blastocysts and four of ten (40%) embryos successfully developed into normal baby mice following embryo transfer. This microwell platform, which supports the development of preimplanted embryos and is low-cost, easy to fabricate and operate, we believe, opens opportunities for a wide range of applications in reproductive medicine and cell biology.

Morphokinetic parameters of early embryo development via time lapse monitoring and their effect on embryo selection and ICSI outcomes: a prospective cohort study

PURPOSE

To compare the outcomes of embryos selected via time lapse monitoring (TLM) versus those selected with conventional methods of selection in subfertile women undergoing ICSI.

METHODS

The study population (239 women) was classified into two groups, based on the monitoring method used: Group 1 (TLM) and Group 2 (conventional monitoring). Groups were compared according to the clinical and ICSI cycle characteristics and reproductive outcomes, while transfers were performed at day 2 or 3. Subgroup analyses were performed, in women of both groups according to age and clinical parameters, and in embryos of Group 1 based on their cellular events.

RESULTS

There was a statistically significant difference between the two study groups with regard to the outcome parameters, favoring Group 1 and especially in women >40 years of age. No differences were found in subgroup analyses in participants of both groups, regarding the stimulation protocol used, number of the oocytes retrieved and type of subfertility, while in Group 1 the percentages of "in range" cellular events were higher in certain divisions in ages 35-40, non-smokers, and the GnRH-agonist group, and in embryos that resulted in pregnancy.

CONCLUSION

Morphokinetic parameters of early embryo development via TLM are related to the characteristics of subfertile patients and associated with ICSI outcomes.

Trends, fads and ART!

Morphological selection techniques of gametes and embryos are of current interest to clinical practice in ART. Although intracytoplasmic morphologically selected sperm injection (IMSI), time lapse imaging morphometry (TLIM) or quantification of chromosome numbers (PGS) are potentially useful in research, they have not been shown to be of statistically predictive value and, thus, have only limited clinical usefulness. We make the point that morphological markers alone cannot predict the success of the early embryo, which depends on the correct orchestration of a myriad of physiological and biochemical activation events that progress independently of the maternal or zygotic genome. Since previous attempts to identify metabolic markers for embryo quality have failed and there is no evidence that the intrinsic nature of gametes and embryos can be improved in the laboratory, embryologists can only minimize environmental or operator induced damage while these cells are manipulated ex vivo.

Diagnosis of human preimplantation embryo viability

BACKGROUND

Transfer of more than a single embryo in an IVF cycle comes with the finite possibility of a multiple gestation. Even a twin pregnancy confers significant risk to both mother and babies. The move to single-embryo transfer for all patients will be greatly facilitated by the ability to quantify embryo viability. Developments in time-lapse incubation systems have provided new insights into the developmental kinetics of the human preimplantation embryo. Advances in molecular methods of chromosomal analysis have created platforms for highly effective screening of biopsied embryos, while noninvasive analysis of embryo physiology reveals more about the embryo than can be determined by morphology alone.

METHODS

Recent developments in time-lapse microscopy, molecular karyotyping and in proteomics and metabolomics have been assessed and presented here in a descriptive review.

RESULTS AND CONCLUSIONS

New algorithms are being created for embryo selection based on their developmental kinetics in culture, and the impact of factors such as patient etiology and treatment are being clarified. Potential links between morphokinetic data and embryo karyotype are being elucidated. The introduction of new molecular methods of determining embryo chromosomal complement is proving to be accurate and reproducible, with the future trending toward CGH arrays or next generation sequencing as a rapid and reliable means of analysis, that should be suitable for each IVF clinic to adopt. A relationship between embryo metabolism and viability is established and is now being considered together with morphokinetic data to create more robust algorithms for embryo selection. Microfluidic devices have the capacity and potential to be used in human IVF clinics for the routine diagnosis of embryo biomarkers.

Relative kinetic expressions defining cleavage synchronicity are better predictors of blastocyst formation and quality than absolute time points

PURPOSE

Morphology alone is not enough for the selection of the embryo (s) with the highest implantation potential and time-lapse imaging has added embryo development kinetics as another selection criterion. Therefore, a combination of morphology with kinetics has inspired a new field termed "morphokinetics", providing a new way of evaluating and selecting embryos. The aim of the study was to identify a criterion solely based on morphokinetic data and available up to the 8-cell stage (t8) to predict blastocyst formation and quality.

METHODS

The study included 3,354 embryos, with annotations up to t8, and cultured until day 5 from 626 infertile patients. A total of 17 kinetic expressions, either absolute cleavage timings and time intervals or time ratios were tested retrospectively for the prediction of blastocyst formation and quality.

RESULTS

Relative timings (t8-t5, the cleavage synchronicity from 4 to 8 cells and from 2 to 8 cells) were found to be better indicators of blastocyst formation and quality when compared to absolute time-points. Especially, the cleavage synchronicity from 2 to 8 cells (CS2-8) = ((t3-t2) + (t5-t4))/(t8-t2)) was found to be the best predictor available on day 3 for blastocyst formation and quality (AUC:0.786; sensitivity: 83.43; specificity: 62.46).

CONCLUSIONS

Time intervals and relative ratios based on selected cleavage cycles defining synchronicity allowed a specific analysis providing high predictivity of blastocyst formation and quality.

Why we should not select the faster embryo: lessons from mice and cattle

Many studies have shown that in vitro culture can negatively impact preimplantation development. This necessitates some selection criteria for identifying the best-suited embryos for transfer. That said, embryo selection after in vitro culture remains a subjective process in most mammalian species, including cows, mice and humans. General consensus in the field is that embryos that develop in a timely manner have the highest developmental competence and viability after transfer. Herein lies the key question: what is a timely manner? With emerging data in bovine and mouse supporting increased developmental competency in embryos with moderate rates of development, it is time to question whether the fastest developing embryos are the best embryos for transfer in the human clinic. This is especially relevant to epigenetic gene regulation, including genomic imprinting, where faster developing embryos exhibit loss of imprinted methylation, as well as to sex selection bias, where faster developmental rates of male embryos may lead to biased embryo transfer and, in turn, biased sex ratios. In this review, we explore evidence surrounding the question of developmental timing as it relates to bovine embryo quality, mouse embryo quality and genomic imprint maintenance, and embryo sex.

Choosing the best embryo by time lapse versus standard morphology

Within the past few years the morphological evaluation of in vitro fertilized embryos has been extended to include continuous surveillance, enabled by the introduction of time-lapse incubators developed specifically for IVF treatment. As a result time-lapse monitoring has been implemented in many clinics worldwide. The proposed benefits compared with culture in a standard incubator and fixed time-point evaluation are uninterrupted culture, a flexible workflow in the laboratory, and improved embryo selection. The latter is based on the reasonable assumption that more frequent observations will provide substantially more information on the relationship between development, timing, and embryo viability. Several retrospective studies have confirmed a relationship between time-lapse parameters and embryo viability evaluated by developmental competence, aneuploidy, and clinical pregnancy. Furthermore a much anticipated randomized study has shown improved pregnancy rates (PRs) after culture in a time-lapse incubator combined with selection using a hierarchical time-lapse selection model. At present this is the only randomized study on possible benefits of time lapse in human embryology. Strict evidence may still seem too weak to introduce time lapse in routine clinical setting. This aim of this review is therefore to perform a balanced discussion of the evidence for time-lapse monitoring.

Embryo selection: the role of time-lapse monitoring

In vitro fertilization has been available for over 3 decades. Its use is becoming more widespread worldwide, and in the developed world, up to 5% of children have been born following IVF. It is estimated that over 5 million children have been conceived in vitro. In addition to giving hope to infertile couples to have their own family, in vitro fertilization has also introduced risks as well. The risk of multiple gestation and the associated maternal and neonatal morbidity/mortality has increased significantly over the past few decades. While stricter transfer policies have eliminated the majority of the high-order multiples, these changes have not yet had much of an impact on the incidence of twins. A twin pregnancy can be avoided by the transfer of a single embryo only. However, the traditionally used method of morphologic embryo selection is not predictive enough to allow routine single embryo transfer; therefore, new screening tools are needed. Time-lapse embryo monitoring allows continuous, non-invasive embryo observation without the need to remove the embryo from optimal culturing conditions. The extra information on the cleavage pattern, morphologic changes and embryo development dynamics could help us identify embryos with a higher implantation potential. These technologic improvements enable us to objectively select the embryo(s) for transfer based on certain algorithms. In the past 5-6 years, numerous studies have been published that confirmed the safety of time-lapse technology. In addition, various markers have already been identified that are associated with the minimal likelihood of implantation and others that are predictive of blastocyst development, implantation potential, genetic health and pregnancy. Various groups have proposed different algorithms for embryo selection based on mostly retrospective data analysis. However, large prospective trials are needed to study the full benefit of these (and potentially new) algorithms before their introduction into daily practice can be recommended.

Quantitative single-cell approaches to stem cell research

Understanding the molecular control of cell fates is central to stem cell research. Such insight requires quantification of molecular and cellular behavior at the single-cell level. Recent advances now permit high-throughput molecular readouts from single cells as well as continuous, noninvasive observation of cell behavior over time. Here, we review current state-of-the-art approaches used to query stem cell fate at the single-cell level, including advances in lineage tracing, time-lapse imaging, and molecular profiling. We also offer our perspective on the advantages and drawbacks of available approaches, key technical limitations, considerations for data interpretation, and future innovation.

No evidence of association between blastocyst aneuploidy and morphokinetic assessment in a selected population of poor-prognosis patients: a longitudinal cohort study

Recent studies involving a limited number of patients have indicated a correlation between aneuploidy and various morphokinetic parameters during preimplantation development. The results among different groups, however, have been inconsistent in identifying the parameters that are able to predict chromosomal abnormalities. The aim of this study was to investigate whether aneuploidy of human blastocysts was detectable by specific morphokinetic parameters in patients at increased risk of aneuploidy because of advanced maternal age, history of unsuccessful IVF treatments, or both. A longitudinal cohort study was conducted using 455 blastocysts from 138 patients. Morphokinetic features of preimplantation development were detected in a timelapse incubator. Blastocysts were subjected to trophectodermal biopsy and comprehensive chromosomal screening. Analyses were conducted by means of logistic mixed-effects models, with a subject-specific intercept. No statistical correlation between 16 commonly detected morphokinetic characteristics of in-vitro embryo development and aneuploidy was found. Results suggest that morphokinetic characteristics cannot be used to select euploid blastocysts in poor-prognosis patients regarded as candidates for pre-implantation genetic screening.

Computer-automated time-lapse analysis results correlate with embryo implantation and clinical pregnancy: a blinded, multi-centre study

Computer-automated time-lapse analysis has been shown to improve embryo selection by providing quantitative and objective information to supplement traditional morphology. In this multi-centre study, the relationship between such computer-derived outputs (High, Medium, Low scores), embryo implantation and clinical pregnancy were examined. Data were collected from six clinics, including 205 patients whose embryos were imaged by the Eeva(TM) System. The Eeva scores were blinded and not considered during embryo selection. Embryos with High and Medium scores had significantly higher implantation rates than those with Low scores (37% and 35% versus 15%; P < 0.0001; P = 0.0004). Similar trends in implantation rates were observed in different IVF centres each using their own protocols. Further analysis revealed that patients with at least one High embryo transferred had significantly higher clinical pregnancy rates than those with only Low embryos transferred (51% versus 34%; P = 0.02), although patients' clinical characteristics across groups were comparable. These data, together with previous research and clinical studies, confirm that computer-automated Eeva scores provide valuable information, which may improve the clinical outcome of IVF procedures and ultimately facilitate the trend of single embryo selection.

Mitochondrial DNA in Day 3 embryo culture medium is a novel, non-invasive biomarker of blastocyst potential and implantation outcome

In assisted reproduction technology, embryo competence is routinely evaluated on morphological criteria. Over the last decade, efforts in improving non-invasive embryo assessment have looked into the secretome of embryos. Human embryos release genomic DNA (gDNA) and mitochondrial DNA (mtDNA) into the culture medium, and the mtDNA/gDNA ratio is significantly correlated with embryo fragmentation. Here, we investigate whether mtDNA/gDNA ratio in embryo spent medium is correlated with blastulation potential and implantation. The mtDNA/gDNA ratio was assessed in 699 Day 3 culture media by quantitative polymerase chain reaction (qPCR) to investigate its correlation with embryo morphology, blastocyst development and implantation. A logistic regression model evaluated whether mtDNA/gDNA ratio in the secretome may improve the prediction of blastulation. We found that embryos that successfully developed into blastocysts exhibited a significantly higher mtDNA/gDNA ratio in the culture medium compared with those that arrest (P = 0.0251), and mtDNA/gDNA, combined with morphological grading, has the potential to predict blastulation better than morphology alone (P = 0.02). Moreover, mtDNA/gDNA ratio was higher in the media from good-quality embryos that reached the full blastocyst stage on Day 5 compared with those that developed more slowly (P < 0.0001). With respect to blastocyst morphology, higher trophectoderm quality was associated with a higher mtDNA/gDNA ratio in the culture medium. Finally, a high mtDNA/gDNA ratio in spent medium was associated with successful implantation outcome (P = 0.0452) of good-quality embryos. In summary, the mtDNA/gDNA ratio in the Day 3 embryo secretome, in combination with morphological grading, may be a novel, non-invasive, early biomarker to improve identification of viable embryos with high developmental potential.

Time-lapse videography of human oocytes following intracytoplasmic sperm injection: events up to the first cleavage division

A total of 341 fertilized and 37 unfertilized oocytes from 63 intracytoplasmic sperm injection (ICSI) treatment cycles were included for retrospective assessment using the Embryoscope time-lapse video system. The second polar body (pb2) extrusion occurred at 2.9±0.1 h (range 0.70-10.15 h) relative to sperm injection. All oocytes reduced in size following sperm injection (p<0.05) with shrinkage ceasing after 2h in the unfertilized and at pb2 extrusion in the fertilized oocytes. Pb2 extrusion was significantly delayed for women aged >38 years compared to those <35 years (3.4±0.2 vs. 2.8±0.1, p<0.01) or 35-38 years (3.4±0.2 vs. 2.8±0.1, p<0.01), but timing was not related to the Day 3 morphological grades (1-4) of subsequent embryos (2.9±0.1, 2.9±0.1, 2.8±0.2 and 3.0±0.1; p>0.05 respectively). A shorter time of first cleavage division relative to either sperm injection or pb2 extrusion is associated with both top grade (AUC=0.596 or 0.601, p=0.006 or 0.004) and usable embryos (AUC=0.638 or 0.632, p=0.000 respectively) on Day 3. In summary, (i) pb2 of human oocytes extrudes at various times following sperm injection, (ii) the timing of pb2 extrusion is significantly delayed when female age >38 years, but not related to subsequent embryo development, (iii) all human oocytes reduce in size following sperm injection, (iv) completion of pb2 extrusion in the fertilized oocytes is a pivotal event in terminating shrinkage of the vitellus, and (v) time to first cleavage division either from sperm injection or pb2 extrusion is a significant predictive marker for embryo quality on Day 3.