High Implantation Potential Research Articles

Novel embryo selection techniques to increase embryo implantation in IVF attempts.

The final success of an IVF attempt depends on several steps and decisions taken during the ovarian stimulation, the oocyte retrieval, the embryo culture and the embryo transfer. The final selection of the embryos most likely to implant is the final step in this process and the responsibility of the lab. Apart from strict morphologic criteria that historically have been used in embryo selection, additional information on genetic, metabolomic and morphokinetic characteristics of the embryo is recently combined to morphology to select the embryo most likely to produce a pregnancy. In this manuscript, we review the most recent information on the current methods used for embryo selection presenting the predictive capability of each one. A literature search was performed on Pubmed, Medline and Cochrane Database of Systematic Reviews for published studies using appropriate key words and phrases with no limits placed on time. It seems that the combination of morphologic criteria in conjunction to embryo kinetics as documented by time-lapse technology provides the most reliable information on embryo quality. Blastocyst biopsy with subsequent comprehensive chromosome analysis allows the selection of the euploid embryos with the higher implantation potential. Embryo time-lapse imaging and blastocyst biopsy combined to comprehensive chromosome analysis are the most promising technologies to increase pregnancy rates and reduce the possibility of multiple pregnancies. However, further studies will demonstrate the capability of routinely using these technologies to significantly improve IVF outcomes.

A comparison between fresh euploid embryo transfer at late day 5 versus day 6

Comprehensive chromosome screening (CCS) allows for selection of euploid blastocysts with high implantation potential. While there are multiple CCS platforms available, qPCR is the only method that can be completed within 4 hours from the time of biopsy. Recently, frozen euploid single embryo transfer was found to significantly improve clinical pregnancy compared to a fresh transfer. It has been proposed that high estrogen levels during ovarian stimulation can be detrimental to the endometrial environment.

Effects of early cleavage patterns of human embryos on subsequent in vitro development and implantation

To establish a noninvasive selection system of human embryos with a high implantation potential before transferring. Cohort study. Independent IVF clinics. One hundred sixty-four patients, with 791 embryos fertilized, checked, and recorded. Embryos were divided into nine groups according to the number of cells they contained and the extent of their fragmentation during the first and second divisions. We examined the effects of the cell division pattern and division time of embryos on subsequent development invitro and invivo using a time-lapse incubator. Rates of blastocyst formation, high-quality blastocyst formation, and pregnancy. The rates of embryos developed into blastocysts and blastocysts in which both the inner cell mass and trophectoderm grades were scored B or higher (good-quality blastocysts) were high in groups that formed two cells during the first division and four cells during the second division, regardless of the presence or absence of fragmentation. In these groups the first and second division times (25.90 and 37.88hours after culture, respectively) of embryos developed into good-quality blastocysts were significantly shorter than those of other embryos. Although embryo selection based on the first and second division times did not affect the pregnancy rates after transfer at day 2 or 3 of culture, it improved the pregnancy rates after blastocyst transfer at day5. Transfer of blastocysts derived from embryos that completed first and second divisions within 25.90 and 37.88hours after culture, respectively, brings about high pregnancy rates.

Selecting the embryo with the highest implantation potential using a data mining based prediction model.

BackgroundEmbryo selection has been based on developmental and morphological characteristics. However, the presence of an important intra-and inter-observer variability of standard scoring system (SSS) has been reported. A computer-assisted scoring system (CASS) has the potential to overcome most of these disadvantages associated with the SSS. The aims of this study were to construct a prediction model, with data mining approaches, and compare the predictive performance of models in SSS and CASS and to evaluate whether using the prediction model would impact the selection of the embryo for transfer.MethodsA total of 871 single transferred embryos between 2008 and 2013 were included and evaluated with two scoring systems: SSS and CASS. Prediction models were developed using multivariable logistic regression (LR) and multivariate adaptive regression splines (MARS). The prediction models were externally validated with a test set of 109 single transfers between January and June 2014. Area under the curve (AUC) in training data and validation data was compared to determine the utility of the models.ResultsIn SSS models, the AUC declined significantly from training data to validation data (p < 0.05). No significant difference was detected in CASS derived models. Two final prediction models derived from CASS were obtained using LR and MARS, which showed moderate discriminative capacity (c-statistic 0.64 and 0.69 respectively) on validation data.ConclusionsThe study showed that the introduction of CASS improved the generalizability of the prediction models, and the combination of computer-assisted scoring system with data mining based predictive modeling is a promising approach to improve the selection of embryo with the highest implantation potential.Electronic supplementary materialThe online version of this article (doi:10.1186/s12958-016-0145-1) contains supplementary material, which is available to authorized users.

Stimulation and aneuploidy: Why are milder stimulation protocols better?

There is an ever-increasing trend in assisted reproductive techniques to reduce the intensity of ovarian stimulation for in vitro fertilization (IVF) and to restrict the number of embryos that are transferred into the uterine cavity. Recent findings suggest that the magnitude of ovarian stimulation affects the proportion of euploid embryos. Ovarian stimulation regimens for IVF seem to have a deleterious effect on oocyte quality and embryo aneuploidy in a dose-dependent manner. We are moving to a global era of single embryo transfers and now it becomes more important than ever before to ensure that this single embryo has the highest implantation potential. Strategies are being adopted to improve the accuracy for selecting euploid, viable embryos for transfer. One such strategy involves further refinement of morphological criteria associated with improved viability by considering, for example, pronuclei disposition, nucleolar organization, and identification of the fast-cleaving embryos, with only mononucleate blastomeres and trying to correlate morphokinetics with cytogenetics. Another strategy employs preimplantation genetic diagnosis whereby a biopsied blastomere is tested for ploidy using next-generation sequencing. Even in older patients, lower oocyte yields may represent a more appropriate response to ovarian stimulation, allowing the most competent follicles and oocytes to develop and thereby reducing the occurrence of embryo aneuploidy. IVF Lite plus ACCUVIT by repeated mild stimulation cycles with subsequent vitrification of blastocysts, combined with preimplantation genetic screening, is a promising new approach for poor responders as well as women of advanced maternal age.

Limitations and controversies in determining the predictive value of oocyte and embryo morphology criteria

In order to increase the success rate of in vitro fertilization cycles, several studies have focused on the identification of the embryo with higher implantation potential. Despite recent advances in the reproductive medicine, based on the OMICs technology, routinely applicable methodologies are still needed. Thus, in most fertilization centers embryo selection for transfer is still based on morphological parameters evaluated under light microscopy. Several morphological parameters may be evaluated, ranging from the pronuclear to blastocyst stage. In general, despite the day of transfer, some criteria are suggested to present a predictive value for embryo viability when analyzed independently or combined. However, the subjectivity of morphological evaluation, as well as the wide diversity of embryo classification systems used by different fertilization centers shows contrasting results, making the implementation of a consensus regarding different morphological criteria and their predictive value a difficult task. The optimization of embryo selection represents a large potential to increase treatment success rates, allowing the transfer of a reduced number of embryos and minimizing the risks of multiple pregnancy.

CUMULUS CELL GENES AS POTENTIAL BIOMARKERS OF OOCYTE AND EMBRYO DEVELOPMENTAL COMPETENCE.

Bogomoletz Institute of Physiology NASU, Ukraine, Kiev. The selection of embryos with high implantation potential is the most important task in assisted reproductive technology. Today, this selection is based on subjective morphological criteria such as growth rate, early cleavage, the degree of fragmentation, blastocyst formation. However, the morphological assessment alone does not accurately predict oocyte/early stage embryo competence. Thus, the development of an objective, accurate, fast and affordable tests to determine oocyte quality and embryo viability could increase the chance of a successful pregnancy and reduce the number of embryos to transfer. The advent of new technologies, the so-called OMIKS, has allowed to identify novel biomarkers that can be used in cycle of in vitro fertilization (IVF) for oocyte and / or embryo selection. During folliculogenesis oocyte plays a dominant role in regulation of cumulus (CC) and granulosa cell (GC) functions, and it is consequently believed that functions of GC and CC indirectly reflect oocyte’s competence. Cell functions and active cell processes are regulated through gene expression therefore, gene expression analysis in GC and/or CC could provide a non-invasive method for identification of the most competent oocytes and embryos. In cumulus cells, genes have been identified that characterize the oocyte ability to undergo meiotic maturation, successful fertilization and early embryonic development. Among them cyclooxygenase 2, gremlin 1 and hyaluronan synthase-2, which play an important roles during oocyte development, ovulation and fertilization. This article reviews the recent data regarding these genes as potential biomarkers for selection of oocytes and embryos in the IVF program.

Evaluation of a high implantation potential (HIP) embryo grading system designed to reduce multiple pregnancy

AimsAlthough we have progressed a long way in performing in vitro fertilization, one hurdle that still remains is the assessment of embryos. The aim of the current paper was to evaluate an embryo selection protocol based on the presence of high implantation potential (HIP) embryos on Day 3 embryo transfer outcomes. MethodsThe analysis of cycles from 6573 IVF cycles in a private fertility clinic was done. Patients included IVF couples having day 3 embryos transferred. Rates of clinical pregnancy, twinning, and high order multiples (HOM) were investigated. ResultsWhen one or more HIP embryos were present in the cohort, there were no significant differences in clinical pregnancy rates when the decision was made to reduce the scheduled number of embryos to transfer by 1, that is, when comparing 2 embryos transferred with 2 reduced to 1, 3 with 3 reduced to 2, or 4 with 4 reduced to 3. Twinning rates were the same when at least 2 embryos were transferred and high order multiple rates were not different when at least 3 embryos were transferred. The presence of HIP embryos increases the chance of pregnancy when 1–2 embryos are transferred. With 3–4 embryos, the presence or absence of a HIP embryo becomes less of a factor in establishing pregnancy. ConclusionsSelecting HIP embryos can reduce the number of embryos transferred without adversely affecting pregnancy rates. Their presence is a strong predictor of pregnancy in patients ≤37 years old.

Selecting the embryo with the highest implantation potential using developmental and morphometric scoring.

Embryo selection has been based on developmental and morphological characteristics. However, the presence of an important intra-and inter-observer variability in the microscopic evaluation of standard scoring system (SSS) has been reported. A golden standard for selection of embryos on day 3 is currently lacking. New technology using multilevel images combined with a computer-assisted scoring system (CASS) has the potential to overcome most of these disadvantages associated with the SSS. The aim of this study was to construct a multivariable prediction model, with data mining approaches, and compare the predictive performance of models in SSS and CASS. A total of 871 single embryo transfers between 2008 and 2013 were included. Embryos were evaluated with two scoring systems: SSS and CASS. Prediction models were developed using multivariable logistic regression (LR) and multivariate adaptive regression splines (MARSplines). The prediction models were externally validated with a test set of 109 single transfers between January and June 2014. Results showed that prediction of implantation was superior using CASS when compared with SSS. With CASS, two final prediction model were obtained using LR and MARSplines, which showed moderate discriminative capacity (c-statistic 0.64 and 0.69 respectively) on validation data. The findings of this study show that combination of computer-assisted scoring system and machine learning based prediction method is a promising approach for in the selection of embryo with the highest implantation potential.

Rapid and noninvasive technique to assess the metabolomics profile of bovine embryos produced in vitro by Raman spectroscopy.

Morphological assessments are used to select embryos with the highest implantation potential, however it is still very limited. The development of new technologies, such as Raman spectroscopy have improved quantitative and qualitative analysis, and consequently led to a better characterization of embryos and improvements on the prediction of their potential. Therefore, we propose a method based on the conventional in vitro culture system of bovine embryos, and the subsequent analysis of the culture media drops by Raman spectroscopy. Our results obtained by PCA analysis clearly showed a separation of the spectral profiles from culture media drops with and without embryos.

The Ideal Stimulation Protocol: Is There One?

The first successful in vitro fertilization (IVF) attempt and most treatment cycles for a while thereafter were conducted in spontaneous menstrual cycles. Nevertheless, realization that availability of a crop of mature oocytes markedly increased chances of success in this therapy prompted most centers to adopt some form of controlled ovarian hyperstimulation (COH). At the outset, clomiphene citrate alone or in combination with human menopausal gonadotropins (hMG) was used, but eventually exogenous gonadotropins emerged as the sole stimulatory drug for COH. Exogenous gonadotropins, and specifically hMG products, have been used in the treatment of infertility since the 1960s, when the first hMG product became available. Subsequently, over the last 25 years, they have become the mainstay of fertility treatment worldwide. The gonadotropins are indicated in isolation as a treatment to induce ovulation, normally in cases where Clomiphene has failed or as a first-line treatment in specific cases of amenorrhea. They are also indicated for Hypogonadotropic hypogonadism in men and women. The most widespread use of gonadotropins is for women undergoing superovulation within a medically assisted reproductive program, like IVF. Superovulation is the stimulation of the ovaries to produce more than one follicle, which enables several embryos to be created. We are still in the search for that “perfect” or “ideal” ovarian stimulation protocol combining both GnRH analogs and gonadotropins that will give us an “adequate” number of oocytes; these oocytes should be of good quality resulting into embryos with a very good morphokinetic score [1] with a high implantation potential and with elimination of ovarian hyperstimulation syndrome (OHSS). The resulting pregnancies should carry to term as a result of the optimal uterine and endocrinological environment that has resulted as a consequence of using that “ideal” stimulation protocol. In the quest for that perfect stimulation protocol, we must imbibe knowledge of the use of GnRH analogs and gonadotropins in different endocrine milieus such as “poor responders” and from natural and artificially stimulated hypogonadotropic hypogonadic states. Newer Gonadotropin preparations are being introduced continuously over the past few years in the quest of that “perfect” but elusive stimulation protocol. Research and practice in the field has led to the era of “Individualized” treatment protocols in the last decade [2, 3].

Preimplantation development of human embryos with numerical chromosome abnormalities in vitro

The study was focused on morphokynetic characteristics of in vitro cultured human embryos that were considered to be aneuploid or euploid according to the preimplantation genetic screening results. Among all the embryos examined only 34.2% were chromosomally balanced, while others possessed isolated or combined chromosome abnormalities. Although morphological features of cleaving pathologic and euploid embryos did not differ significantly, on the fifth day of culture chromosomally balanced specimen formed "expanded" blastocyst twice as frequently as abnormal ones. Moreover, development of 38.4% of aneuploid embryos was compromised before the initiation of cavitation. Thus, prolonged embryo culture advances selection of samples with the highest implantation potential for the transfer on the basis of the morphokynetic characteristics and helps to avoid additional genetic testing.

Microarray Pre-Implantation Genetic Screening Significantly Improves Clinical Outcomes with Vitrified-Thawed Embryo Transfer

Selecting embryos with the highest implantation potential is one of the most important challenges in the field of Assisted Reproduction. Previously, morphologic criteria were the most commonly used standards for embryo selection. The introduction of pre-implantation genetic screening (PGS-24) provides a novel method to determinate embryo competence. Our goal was to evaluate the clinical outcomes in patients using vitrified-thawed blastocysts with and without PGS-24 testing.

Patients Often Ask if They Should Vitrify Grade C/Fair Quality Blastocysts; Tell Them Yes, as They Can Result in Almost a 30% Frozen Embryo Transfer Pregnancy Rate

The advent of effective blastocyst culture and vitrification has allowed significantly increased implantation rates in frozen embryo transfer (FET) cycles. In fact, recent evidence suggests that FET cycles may have high implantation potential due to increased uterine receptivity. However, not all embryos reach the same quality at the time of vitrification (overall grade range: A/Great, B/Good or C/Fair). Embryologists spend years developing and refining the skills necessary to classify blastocysts, allowing for affective decisions about which blastocysts to vitrify.

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

PurposeMorphology 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.MethodsThe 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.ResultsRelative 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).ConclusionsTime intervals and relative ratios based on selected cleavage cycles defining synchronicity allowed a specific analysis providing high predictivity of blastocyst formation and quality.Electronic supplementary materialThe online version of this article (doi:10.1007/s10815-014-0341-x) contains supplementary material, which is available to authorized users.

Reply: Clinical outcomes following selection of human preimplantation embryos with time-lapse monitoring: a systematic review

BACKGROUND Time-lapse monitoring (TLM) has emerged as a novel technology to perform semi-quantitative evaluation of embryo morphology and developmental kinetics in assisted reproduction. While this method has already been introduced into clinical practice in many laboratories, it is unclear whether it adds value to conventional morphology. Most studies only report blastocyst formation as the primary end-point. The aim of this systematic review is to provide a critical evaluation of the available studies that report clinical outcomes following embryo selection with TLM. METHODS A literature search in MEDLINE, Cochrane CENTRAL and ISI Web of Knowledge Science Citation Index was performed to identify studies that assess the clinical utility of kinetic markers for non-invasive selection of human embryos with high implantation potential. Only studies published before 31 December 2013 in the English language that report rates of implantation, clinical pregnancy or live birth were included. RESULTS Two hundred and fifty-one studies were identified by database search and reference list review; only 13 met eligibility criteria and were included in this analysis. The following morphokinetic parameters were assessed: pronuclear dynamics and morphology (n = 3), duration of first cytokinesis and reappearance of nuclei after cleavage (n = 3), time to various cleavage stages (n = 5), duration of various cleavage stages (n = 6), duration of cleavage cycles and mitotic synchronicity (n = 6), and time to morula, blastocyst and hatching (n = 4). Five studies used combined parameter grading to generate a cumulative score, and two studies retrospectively compared implantation rates following embryo selection by conventional morphology alone or with the addition of a hierarchal time-lapse classification. While several studies suggest higher implantation rates for fast-cleaving embryos and those with a timely duration (i.e. all time points within the defined ranges) of the 2-cell and 3-cell stages, no single morphokinetic parameter has been consistently shown to predict implantation potential. Furthermore, there was considerable disagreement regarding not only which parameters are useful, but also what constitutes normal and abnormal intervals for these measurements. CONCLUSIONS While TLM has the potential to revolutionize clinical embryology, there are currently no high-quality data to support the clinical use of this technology for selection of human preimplantation embryos. Our recommendations for the adoption of this technique are thus limited by the available literature and the lack of robust prospective studies reporting clinical outcomes. Sparse, often incomplete and largely heterogeneous data suggest that TLM may be able to distinguish between high and low-implantation potential embryos. Only one study demonstrated significantly improved clinical pregnancy rates when embryos were selected by TLM in addition to conventional morphology. Prospective studies are currently underway and hopefully will clarify the role of TLM. As more data become available, it is of the utmost importance that groups using TLM share a common nomenclature for measured time points; herein, we have proposed a standardized system for describing any milestone along the preimplantation developmental timeline. Furthermore, future studies must publish complete datasets in an effort to define patient-specific algorithms with the clinically meaningful end-point of implantation, prior to routine adoption in the assisted reproduction technology laboratory. Until such evidence accumulates, selection of embryos by TLM should remain an experimental strategy subject to institutional review and approval.

Microarray preimplantation genetic screen significantly improves clinical outcomes with vitrified-thawed embryo transfer

Selecting embryos with the highest implantation potential is the most important challenges in the field of Assisted Reproduction. Previously, morphologic criteria were the most commonly used standards for embryo selection. The introduction of preimplantation genetic screen (PGS-24) provides a novel method to determinate embryo competence. Our goal was to evaluate the clinical outcomes in patients with and without PGS-24 testing.

A minimally invasive methodology based on morphometric parameters for day 2 embryo quality assessment

The risk of multiple pregnancy to maternal–fetal health can be minimized by reducing the number of embryos transferred. New tools for selecting embryos with the highest implantation potential should be developed. The aim of this study was to evaluate the ability of morphological and morphometric variables to predict implantation by analysing images of embryos. This was a retrospective study of 135 embryo photographs from 112 IVF–ICSI cycles carried out between January and March 2011. The embryos were photographed immediately before transfer using Cronus 3 software. Their images were analysed using the public program ImageJ. Significant effects (P < 0.05), and higher discriminant power to predict implantation were observed for the morphometric embryo variables compared with morphological ones. The features for successfully implanted embryos were as follows: four cells on day 2 of development; all blastomeres with circular shape (roundness factor greater than 0.9), an average zona pellucida thickness of 13 µm and an average of 17695.1 µm2 for the embryo area. Embryo size, which is described by its area and the average roundness factor for each cell, provides two objective variables to consider when predicting implantation. This approach should be further investigated for its potential ability to improve embryo scoring.

Clinical outcomes following selection of human preimplantation embryos with time-lapse monitoring: a systematic review.

Time-lapse monitoring (TLM) has emerged as a novel technology to perform semi-quantitative evaluation of embryo morphology and developmental kinetics in assisted reproduction. While this method has already been introduced into clinical practice in many laboratories, it is unclear whether it adds value to conventional morphology. Most studies only report blastocyst formation as the primary end-point. The aim of this systematic review is to provide a critical evaluation of the available studies that report clinical outcomes following embryo selection with TLM. A literature search in MEDLINE, Cochrane CENTRAL and ISI Web of Knowledge Science Citation Index was performed to identify studies that assess the clinical utility of kinetic markers for non-invasive selection of human embryos with high implantation potential. Only studies published before 31 December 2013 in the English language that report rates of implantation, clinical pregnancy or live birth were included. Two hundred and fifty-one studies were identified by database search and reference list review; only 13 met eligibility criteria and were included in this analysis. The following morphokinetic parameters were assessed: pronuclear dynamics and morphology (n = 3), duration of first cytokinesis and reappearance of nuclei after cleavage (n = 3), time to various cleavage stages (n = 5), duration of various cleavage stages (n = 6), duration of cleavage cycles and mitotic synchronicity (n = 6), and time to morula, blastocyst and hatching (n = 4). Five studies used combined parameter grading to generate a cumulative score, and two studies retrospectively compared implantation rates following embryo selection by conventional morphology alone or with the addition of a hierarchal time-lapse classification. While several studies suggest higher implantation rates for fast-cleaving embryos and those with a timely duration (i.e. all time points within the defined ranges) of the 2-cell and 3-cell stages, no single morphokinetic parameter has been consistently shown to predict implantation potential. Furthermore, there was considerable disagreement regarding not only which parameters are useful, but also what constitutes normal and abnormal intervals for these measurements. While TLM has the potential to revolutionize clinical embryology, there are currently no high-quality data to support the clinical use of this technology for selection of human preimplantation embryos. Our recommendations for the adoption of this technique are thus limited by the available literature and the lack of robust prospective studies reporting clinical outcomes. Sparse, often incomplete and largely heterogeneous data suggest that TLM may be able to distinguish between high and low-implantation potential embryos. Only one study demonstrated significantly improved clinical pregnancy rates when embryos were selected by TLM in addition to conventional morphology. Prospective studies are currently underway and hopefully will clarify the role of TLM. As more data become available, it is of the utmost importance that groups using TLM share a common nomenclature for measured time points; herein, we have proposed a standardized system for describing any milestone along the preimplantation developmental timeline. Furthermore, future studies must publish complete datasets in an effort to define patient-specific algorithms with the clinically meaningful end-point of implantation, prior to routine adoption in the assisted reproduction technology laboratory. Until such evidence accumulates, selection of embryos by TLM should remain an experimental strategy subject to institutional review and approval.

Correlation between embryo morphology and development and chromosomal complement

To analyze the correlation between embryo morphology and the chromosomal status using the array comparative genomic hybridization [array comparative genomic hybridization (a-CGH)] technique for screening 23 chromosome pairs in a single blastomere biopsy from Day 3 embryos. One thousand five hundred and fifty seven embryos were included from 203 cycle ICSI patients undergoing preimplantation genetic screening. The 23 chromosome pairs were analyzed by blastomere biopsy from day 3 embryos using a-CGH array method. Embryo development rate, fragmentation rate and chromosome status of the analyzed blastomeres were recorded and correlated with the aCGH results. The incidence of chromosomal abnormalities was significantly higher in slow-and fast cleaving embryos at day 3 after insemination. The incidence of fragmentation and the type of fragmentation was associated with an increased incidence of chromosomal abnormalities. The symmetry of the blastomeres also correlated with the aneuploidy rates. Embryo development rate and morphological parameter such as degree, type of fragmentation and the symmetry of the blastomeres to a large extent reflect the cytogenetic status of the embryo and thus are important in the selection of embryos with the highest implantation potential.