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Istanbul consensus workshop on embryo assessment: proceedings of an expert meeting,

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Abstract

This paper reports the proceedings of an international consensus meeting on oocyte and embryo morphology assessment. Following background presentations about current practice, the expert panel developed a set of consensus points to define the minimum criteria for oocyte and embryo morphology assessment. It is expected that the definition of common terminology and standardization of laboratory practice related to embryo morphology assessment will result in more effective comparisons of treatment outcomes. This document is intended to be referenced as a global consensus to allow standardized reporting of the minimum dataset required for the accurate description of embryo development.

This paper reports the proceedings and outcomes of an international consensus meeting on human oocyte and embryo morphology assessment. An expert panel developed a series of consensus points to define the minimum criteria for such assessments. The definition of common terminology, and standardization of laboratory practices related to these morphological assessments, will permit more effective comparisons of treatment outcomes around the world. This report is intended to be referenced as a global consensus to allow standardized reporting of the minimum descriptive criteria required for routine clinical evaluations of human embryo development in vitro.

Introduction

Although the advent of ‘-omics’-based technologies may ultimately enhance the non-invasive assessment of human embryos in vitro, there are still no routinely applicable techniques or analytical devices available. Hence, IVF clinics worldwide continue to select embryos for transfer based on their development rate and morphological features as assessed by light microscopy. However, the many variations in embryo grading schemes applied by different clinics make inter-clinic comparisons extremely difficult, if not impossible. Although national consensus schemes exist in some countries, e.g. Spain and the UK, these are relatively few. Having an international consensus on embryo assessment would also help to validate the use of embryo morphology as an endpoint in clinical trials and other studies to assess new technologies and products in IVF, if it were shown to act as at least a partial surrogate for clinical pregnancy outcome – one example might be registration of new drugs for approval by the US Food and Drug Administration. Therefore, it has been suggested that if common primary endpoints based on embryo quality could be defined and validated, it might be possible to develop and register new fertility products and technologies more readily. This is also an extremely important element of the continual drive to improve the safety and efficacy of clinical IVF treatments.

The Alpha Executive, and European Society of Human Reproduction and Embryology (ESHRE) Special Interest Group of Embryology, in response to suggestions and requests from members of both international societies concerning the need for international consensus in the morphological assessment of embryos, convened a 2-day workshop to address this need. The workshop was held on 26–27 February 2010 in Istanbul, Turkey. In order to realize an effective consensus, the meeting had to be sufficiently small to allow consensus to be reached, while at the same time involving enough recognized experts to support the credibility of the consensus. The ultimate goal of the workshop was to establish common criteria and terminology for grading oocytes, zygotes and embryos that would be amenable to routine application in any IVF laboratory.

This report presents the proceedings of this Expert Meeting, incorporating the text of the presentations as well as the consensus points developed.

Section snippets

ESHRE Embryology SIG Atlas project (Cristina Magli)

It is recognized that embryology is the central reference point for all of the Special Interest Groups and Taskforces of ESHRE, and therefore that there is a need for consensus in the way embryos are assessed and described. To work towards this consensus, an Atlas of Embryology was published in 2000 (Gianaroli et al., 2000) using images of oocyte and embryo development submitted by members of the ESHRE Special Interest Group of Embryology.

The next step in this project will be to design an

Spain: the ASEBIR consensus scheme (Gloria Calderón)

Asociación Española para el estudio de la Biología Reproductiva (ASEBIR) is the Spanish society for every professional working in the IVF laboratory. Since embryo morphology is currently the most important factor for the prediction of pregnancy, ASEBIR agreed that a dynamic system of embryo scoring was required that included all stages from gamete to blastocyst. A consensus was reached for scoring, which was then tested in a multicentre trial of IVF laboratories across Spain, with each

Molecular and cellular anatomy of a cytoplasmic dysmorphism in the mature human oocyte: physiological implications for normal development (Jonathan van Blerkom)

It is largely recognized in clinical IVF that the developmental competence of the human embryo is directly influenced by the normality of nuclear (meiotic) and cytoplasmic maturation during the preovulatory period. The detection of certain cytoplasmic irregularities or defects, first termed ‘cytoplasmic dysmorphisms’ by Van Blerkom and Henry (1992), have since been used to select oocytes for insemination or assess the relative developmental competence of early embryos. However, while certain

Assessing fertilization (James Catt)

Assessment of fertilization should be straightforward, as a fertilized oocyte should have two pronuclei and two polar bodies. However, this definition of fertilization is a snapshot from a continuum of events, as has been illustrated through time-lapse photography (Payne et al., 1997). In the time course leading to the initiation of pronuclear formation, zygotes arising from IVF are observed to be approximately 1 h behind those arising from ICSI, provided that the spermatozoa used for IVF have

Fragmentation (Kersti Lundin)

A fragment can be defined as an anuclear, membrane-bound extracellular cytoplasmic structure. The incidence of fragmentation is difficult to evaluate, as it is first necessary to differentiate fragments from cells, and then estimate the relative proportion of the embryo that is fragmented. Johansson et al. (2003) defined fragments as cells that were <45 μm in diameter for day-2 embryos- and <40 μm in diameter for day-3 embryos.

The impact of <10% fragmentation in day-3 embryos on implantation rate

Hierarchy of embryo morphology assessment (Dominique Royère)

While many parameters have been reported to correlate with embryo implantation or blastocyst development, few studies have focused on the interdependence of these parameters, and even fewer have aimed at determining a relative weight for these parameters to predict implantation or developmental potential. However, using this strategy, Sjöblom et al. (2006) identified five parameters (cytoplasmic appearance, pronuclei and nucleoli, cytoplasmic deficit and cell number) as well as the presence of

Historical overview of blastocyst assessment (David Gardner)

The significance of examining the embryo post compaction is the ability to examine it after embryonic genome activation. Furthermore, the obvious benefit of looking at the blastocyst is the ability to examine both of the cell types. The extent to which the TE develops will reflect the embryo’s ability to attach and implant in the endometrium, while development of the ICM is obviously crucial for the development of the fetus itself (Kovacic et al., 2004). There are numerous papers discussing the

Consensus points

Following discussions related to each of the presentations, the following consensus points were developed. It should be noted that these are the first set of consensus recommendations for oocyte and embryo scoring, and will need to be reviewed at regular intervals. In addition, it should be understood that these consensus points represent the ‘minimum standards’ for oocyte and embryo morphology scoring and, as such, do not restrict laboratories from performing additional observations or

Conclusion

It is hoped that these consensus points will form the common language for embryologists worldwide to describe oocyte and embryo morphology. It is understood that some laboratories will continue to score other facets of embryo morphology, and provided that this scoring does not alter the developmental trajectory, these enhancements may provide future prognostic indicators and should be encouraged. However, in the meantime, the use of a common minimum dataset for descriptive scoring system in

Acknowledgements

The Workshop was supported by unrestricted grants from the following (in alphabetical order): IBSA Institut Biochimique SA; Ferring International; Merck Serono SA, and by Alpha and ESHRE. This Proceedings report was compiled by Sharon Mortimer.

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    Alpha Scientists in Reproductive Medicine and ESHRE Special Interest Group of Embryology equally contributed to the document.

    Alpha – Scientists in reproductive medicine – is a non-profit organization which provides an international forum for scientists in reproductive medicine. Alpha’s objectives are to advance the art and science of clinical embryology for the benefit of the public worldwide, through international promotion of education, communication and collaboration. The scope of the Special Interest Group on Embryology (European Society of Human Reproduction and Embryology) is broad, incorporating all from basic scientific advances to laboratory practices and policy influences. This area is the primary interest for many ESHRE members who are interested in the present and future developments of clinical embryology.

    1

    Workshop participants: Başak Balaban∗ (Assisted Reproduction Unit, American Hospital, Istanbul, Turkey), Daniel Brison (Department of Reproductive Medicine, St. Mary’s Hospital, Manchester, UK), Gloria Calderón (IVI-Barcelona, Barcelona, Spain), James Catt (Optimal IVF, Melbourne Vic., Australia), Joe Conaghan (Pacific Fertility Center, San Francisco, CA, USA), Lisa Cowan (Victoria Fertility Centre, Victoria, BC, Canada), Thomas Ebner (Landes- Frauen- und Kinderklinik, IVF-Unit, Linz, Austria), David Gardner (Department of Zoology, University of Melbourne, Melbourne Vic., Australia), Thorir Hardarson (Fertilitetscentrum, Göteborg, Sweden), Kersti Lundin (Sahlgrenska University Hospital, Göteborg, Sweden), M Cristina Magli∗ (SISMER, Bologna, Italy), David Mortimer (Oozoa Biomedical Inc., West Vancouver, BC, Canada), Sharon Mortimer (Oozoa Biomedical Inc., West Vancouver, BC, Canada), Santiago Munné (Reprogenetics, Livingston, NJ, USA), Dominique Royere (Service de Médecine et Biologie de la Reproduction, CHU Bretonneau, Tours, France), Lynette Scott (Fertility Centers of New England, Reading, MA, USA), Johan Smitz (UZBrussel, Vrije Universiteit Brussel, Brussels, Belgium), Alan Thornhill (The London Bridge Fertility, Gynecology and Genetics Centre, London Bridge, UK), Jonathan van Blerkom (Department of Molecular, Cellular and Developmental Biology, University of Colorado, Boulder, CO, USA and Colorado Reproductive Endocrinology, Rose Medical Center, Denver, CO), Etienne Van den Abbeel (University Hospital Gent, Gent, Belgium).

    This consensus document, which has not been subjected to independent peer review by the editors of Reproductive BioMedicine Online, is being published simultaneously by Reproductive BioMedicine Online and Human Reproduction.

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