• PGD is offered to carriers of single-gene disorders such a cystic fibrosis, patients with a family or personal history of inheritable disorders, and carriers of abnormal chromosomes
  

• It may also be used to detect or diagnose genetic disorders causing recurrent pregnancy loss (RPL) or disorders associated with increased reproductive age of the female partner, repeated implantation failure (i.e. multiple failed IVF cycles) and HLA matching
  

• Always used together with IVF
  

• PGD involves removal of a single cell from a 6-8 cell embryo to analyze for genetic abnormalities 
  

• Biopsied embryos are allowed to grow to blastocyst stage
  

• Those embryos that are genetically "normal" can be selected for transfer back into the uterus
  

Limitations of PGD

• Requires large enough numbers of embryos to allow transfer at the blastocyst stage
  

• Often, no additional embryos are available for freezing
  

• Risk of no embryos for transfer
  

• Misdiagnosis 
  

• Low risk of damage to the embryo during biopsy