Mosaicism Gatekeepers Conference

To Transfer or Not to Transfer – Consequences and Risks Surrounding Mosaic Embryos.

January 26th, 2018
8:30 am to 3:00pm
Hilton DoubleTree Hotel, Downtown Toronto
108 Chestnut St, Toronto, ON M5G 1R3


There is considerable controversy over the shortcomings of Preimplantation Genetic Screening (PGS) or Comprehensive Chromosomal Screening (CCS). This symposium will address the controversies and questions that arise when considering the question of what all stakeholders should do with the mosaic embryo. We examine the technology and the frequency with which technology provides inaccurate information concerning euploid embryos, whether the technology is simply “not good enough” and whether or not it should be offered or used at all until it is improved. In addition, we consider, with audience anticipation, potential improvements to the technology.

On a clinical level, we consider the worst case scenario in which a mosaic embryo is actually an aneuploid embryo and is transferred.  In light of this, we consider how to prepare patients for such a transfer. Finally, we examine ethical and legal considerations regarding transfer of the mosaic embryo.

The speakers will address these areas as appropriate. Audience views will be expressed in the two panel discussions incorporated into the Symposium as well as question and answer periods after each talk.


Upon completion of this conference, participants will be able to:

  1. Summarize the principles of PGS/CCS technology
  2. Describe how mosaic embryos develop and how are maintained in the embryology lab
  3. Discuss the ethical considerations surrounding the transfer of a mosaic embryo
  4. Assess the potential emotional impact on patients faced with the possibility of transferring a mosaic embryo
  5. Analyze the science, ethics and patient perspectives in formulating a clinic policy regarding the transfer/disposition of mosaic embryos


[product_category category=”mosaic-embryos-member”]
[product_category category=”mosaic-embryos-non-member”]

The presentation will open with a brief discussion of the history of pre-implantation genetic screening (PGS) and its evolution to Complete Chromosomal Screening (CCS). This will be more a discussion of the science behind the technology including a description of NGS or Next Generation Screening. Mosaic embryos will still exist with the current technology. A discussion of the science behind mosaics as well as the frequency and degrees of mosaicism will be presented. I will present some outcome data available to me based upon the transfer of mosaic embryos. Lastly, I will discuss future options to improve the reliability of CCS such as inner cell mass biopsy as one example.

Learning Objectives:

  1. Review PGS/CCS technology principles
  2. Discuss the science behind mosaicism
  3. Assess outcomes after the transfer of mosaic embryos
  4. Summarize potential future directions of PGS/CCS technology

It is now recognized that the majority of human embryos on day 3 (6 to 8 cell stage) are mosaic, i.e. they contain cells with different chromosomal complements. It is also believed, based on both animal and human studies, that many of these embryos may go on to implant and develop into normal live births. This presentation will discuss possible problems with the ability of day 5 or 6 trophectoderm biopsies to accurately screen for aneuploidy in human embryos and will review the published data concerning the pregnancy outcomes with transfer of mosaic embryos.

Learning Objectives

  1. Discuss why day 3 embryo biopsies for PGS may be inaccurate and actually detrimental to pregnancy outcome.
  2. Describe options to the present use of trophectoderm biopsy for determination of chromosomal aneuploidy
  3. Assess comfort level with the transfer of mosaic (or aneuploid) embryos.

The embryologist is the penultimate step in transferring an embryo. The decision to do so involves a discussion with the clinician who then will discuss the decision with the patient/s. in the case of embryos that have not undergone genetic testing or those that have been tested and found to be euploid, there is little concern regarding the consequences of transferring the embryo. However, where an embryo has been tested with CCS/PGS and found to be mosaic with some cells euploid and others aneuploid, there are potential concerns. The major question remains whether this embryo is truly aneuploid and therefore should not be transferred or are we deciding to discard a normal embryo owing to the presence of aneuploid cells? We need to have insight into what degree of mosaicism is “acceptable”. This is not an easy decision and one that must be decided by a clinic policy in consultation with clinicians, nurses, ethicists and lawyers. If there is a possibility of exposing the patient to risk, embryologists in general have reservations regarding such participation. However, we also have concerns in deciding that a mosaic embryo may be sufficiently euploid that no risk to transfer is present and the embryo should not be discarded. I will discuss the embryologist’s view of mosaicism and highlight the questions and concerns that face our profession.

Learning Objectives

  1. Identify the issues and concerns facing the embryologist when confronted by the prospect of transferring a mosaic embryo
  2. Discuss some specifics of the embryologists’ view into the development of a clinic policy regarding the transfer of mosaic embryos
  3. Consider the contrast in the personal and professional views of an individual embryologist when faced with the prospect of participating in the transfer of a mosaic embryo

A panel discussion with the morning speakers; Tony Gordon, Bob Casper, Scot Hamilton

Lunch will be served in the Mandarin Foyer

It is common knowledge that infertility and reproductive loss impacts patients’ emotional wellbeing significantly. What is not as commonly discussed, is how significantly other aspects of patients’ lives are impacted and how this links to decision-making around treatment. Gaining a deeper understanding of patients’ emotional experience, along with a more comprehensive understanding of patients’ outcome expectations can put their choice to transfer a mosaic/abnormal embryo into a fuller and more realistic context. And in doing so, set a foundation for improved care, in partnering with patients to make thoughtful choices that are best for them.

Learning Objectives

  1. Describe the profound emotional factors underlying patients’ decisions to transfer mosaic/abnormal embryos
  2. Consider expectations regarding outcomes when transferring a mosaic/abnormal embryo
  3. Consider various short and long-term potential ramifications of transferring a mosaic/abnormal embryo

This presentation will provide an overview of key ethical issues identified in the literature about the implantation of embryos identified through preimplantation genetic screening (PGS) as having chromosomal mosaicism. The presentation will use a case example to apply an established ethics-based decision-making tool for clinicians to use in considering cases that arise in their practice.

Learning Objectives

  1. Discuss ethical issues identified in the literature about the implantation of chromosomally mosaic embryos
  2. Identify and describe ethics-based decision-making tools
  3. Utilize an ethics-based decision tool in a practice scenario

Learning Objectives

  1. Describe the potential legal implications of transferring mosaic embryos
  2. Identify what is necessary to meet the requirements of informed consent for transferring mosaic embryos
  3. Identify the legal implications of engaging in experimental medicine
  4. Summarize various opportunities to minimize legal liability
Panel Discussion with all the conference speakers: Shawn Winsor, Sara Cohen, Tony Gordon, Bob Casper, Scot Hamilton

Accreditation Statement

UBCThe University of British Columbia Division of Continuing Professional Development (UBC CPD) is fully accredited by the Committee on Accreditation of Continuing Medical Education (CACME) to provide study credits for continuing medical education for physicians. This event is an Accredited Group Learning Activity (Section 1) as defined by the Maintenance of Certification Program of the Royal College of Physicians and Surgeons of Canada, and approved by UBC CPD. You may claim a maximum of 5.75 hours (credits are automatically calculated). Each physician should claim only those credits he/she actually spent in the activity.