THE SECOND PGD TYPE. A BIOPSY OF BLASTOMERES

A biopsy of blastomeres is carried out on day 3 of embyo development for all embryos obtained in the IVF cycle that have 5 or more blastomeres with a degree of fragmentation not higher than 25%.

The ADVANTAGES are:

• The method allows the analysis not only of meiotic errors of the paternal and the maternal genome but also of mitotic ones;
  
• Enough time for genetic diagnosis;
  
• An embryo transfer in the same cycle;
  
• The biopsy can be repeated.
  
  

The LIMITATIONS are:

• Earlier studies claimed there was no harm for an embryo (Hardy et al., 1989), yet the modern ones speak about embryo damage (Mastenbroek et al, 2007, Scott et al, 2012);
  
• A decrease in the potential of implantation (Cohen et al, 2010);
  
• A high level of chromosomal mosaicism of pre-implantation embryos; a possibility that a healthy embryo can be diagnosed with a pathology, which nullifies the efficacy of diagnosis.
  
  

The consequences of a biopsy of blastomeres for an embryo:

• A decrease in the number of ICM and trophectoderm cells;
  
• A decrease in HCG-producing activity of a trophoblast when implanting embryos that have undergone a biopsy (Yeon Jean Cho et al, 2011).
  
  

Mice derived from embryos that had undergone a biopsy demonstrated:

• A change in the expression of 36 genes;
  
• Hypomielinization of nerve fibers in the brain;
  
• An increased risk of developing neurodegenerative diseases.