Preimplantation Genetic Diagnosis

What is PGD?

Preimplantation Genetic Diagnosis (PGD) is a procedure involving the removal of one or two cells from an embryo and subsequent genetic testing of these cells for specific genetic conditions or chromosomal disorders. Embryos created by IVF can be tested for serious genetic disorders and chromosomal abnormalities using this technology and unaffected embryos can be selected and transferred into the woman’s uterus or frozen for future use.
 

What can we test for?

Some inherited conditions we currently test for include:

  • Haemophilia
  • Cystic Fibrosis
  • ß-Thalassaemia
  • Huntington’s disease
  • Fragile-x
  • Spinal Muscular Atrophy
  • Myotonic Dystrophy

We can also test for chromosomal abnormalities including:

  • Translocations
  • Aneuploidy (chromosome additions or deletions)

 

Who can have PGD?

In New Zealand PGD is permitted for:

  • Serious conditions where a child has at least a 1 in 4 chance of inheriting the condition.
  • Chromosome abnormalities associated with recurrent miscarriage or advanced maternal age.

Ethics Committee approval is required for other reasons, such as ‘saviour siblings’.

PGD cannot be used for social reasons such as gender selection in New Zealand.

 

The Guidelines on Preimplantation Genetic Diagnosis can be found on the Ethics Committee of Assisted Reproductive Technology (ECART) website.

 

The process

Fertility Associates offers ‘Transport Preimplantation Genetic Diagnosis' in partnership with Monash IVF in Melbourne Australia and Canterbury Health Laboratories in Christchurch. Egg collection, in vitro fertilisation and embryo culture all take place in Fertility Associates in Auckland. On day 3 or 5 of embryo development, cells are removed from each viable embryo and sent to Monash IVF or Canterbury Health Laboratories. There the genetic screening and diagnosis is made and the results and recommendations are sent back to Fertility Associates. Our embryologists then select the appropriate embryo(s) for fresh replacement and possible cryopreservation.

 

The techniques used

  • PCR (Polymerase Chain Reaction) is a technique using an enzyme to make millions of copies of a single gene so it can be easily detected.
  • FISH (Fluorescence In Situ Hybridisation) involves staining of selected chromosomes or parts of chromosomes after the cell has been put on a microscope slide. The number of copies of each chromosome or re-arrangements of selected chromosomes can be determined.
  • Microarray CGH (Comparative Genomic Hybridisation) uses enzymes to make millions of copies of small pieces of each chromosome. This makes it possible to count all chromosome copies in an embryo and detect many translocations.

It is also possible to combine microarray CGH with single gene analysis (PCR) increasing the chance that an unaffected, chromosomally normal embryo is selected for replacement.

To find out more about the process, take a look at our PGD Fertility Facts sheet and the IVF section of our Pathway to a Child magazine.

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