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New Methods For Chromosome Screening Of Embryos And Oocytes

Dagan Wells, PhD

 

NEEDS ASSESSMENT

LECTURE DESCRIPTION

      Many factors negatively influence human embryo survival, but chromosome abnormality is believed to be one of the most important. Embryos derived from aneuploid oocytes may arrest during preimplantation development, fail to implant, or spontaneously abort. For this reason some fertility clinics have advocated the use of chromosomal screening to assist in the identification and preferential transfer of chromosomally normal embryos.

       Typical screening strategies involve biopsy of a single blastomere, followed by fluorescent in situ hybridization (FISH) analysis. However, this approach only permits a limited cytogenetic examination and accuracy is reduced by chromosomal mosaicism and problems related to cell-fixation.

      New techniques, such as comparative genomic hybridization (CGH) and microarray analysis, enable screening of every chromosome and avoid fixation of cells onto slides. These advanced cytogenetic methods may improve the accuracy and efficacy of preimplantation genetic screening and expand the range of patients that benefit from this approach.

 

  
   
LECTURE OBJECTIVES

At the end of this presentation the participant should be able to:

  • Recognize chromosome abnormality rates in human oocytes and embryos and be familiar with the theory underlying the use of PGD to screen for aneuploidy.
  • Interpret the current controversy surrounding the use of chromosome screening to assist embryo selection
  • Compare clinical studies that illustrate the benefits of chromosome screening and those studies that have shown no advantage to chromosome screening.
  • Determine the limitations of traditional methods of chromosome screening and be aware of recent advances in methodology that overcome these limitations (e.g. CGH and microarrays).