Fertility treatments | Preimplantation genetic diagnosis

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Preimplantation Genetic Diagnosis

Preimplantation Genetic Diagnosis (PGD) is when the genetic status of each embryo is determined before it is transferred into the uterus. Each embryo created as a consequence of IVF is then biopsied at the 6-10 cell stage (usually on Day 3 after egg pick-up). This biopsy requires a needle to be passed through the zona (shell) of the egg. This needle is similar to, but slightly larger than, the needle used for ICSI. Two cells are taken from the embryo and then the genetic structure analysed.

Until new and better techniques that amplify the genes are developed, the diagnosis is usually made using a technique called "Fluorescence in-situ hybridisation" or more simply

FISH. (Pictured right: FISH image of a cell from a trisomy 21 embryo).

FISH utilises fluorescent probes that are specific for a given chromosome. A mix of several probes of different colours is added to the cell nucleus. The probes attach to their target chromosomes showing up as coloured spots that can be counted to ensure the cell has the correct number. Currently these probes are only available for certain chromosomes including the sex chromosomes. To ensure reliability it is important that both cells biopsied from the embryo show the same genetic picture. If there are abnormalities then that embryo is not replaced.

The Ethics Committee of Assisted Reproductive Technology (ECART) has developed guideline for Preimplantation Genetic Diagnosis. Click here for the MOH website where the guidelines and a discussion document can be found. More detail about PGD is discussed in this document.

Fertility Associates is able to offer ‘transport’ Pre-implantation Diagnosis in partnership with Monash IVF in Melbourne Australia. Egg collection, in vitro fertilisation and embryo culture all take place in Fertility Associates in Auckland. When the embryos are 3 days old, they are biopsied and the cells are sent overnight to Monash IVF. There the genetic screening and diagnosis is made and the results and recommendations sent back to Fertility Associates. Our embryologists then select the appropriate embryo(s) for fresh replacement and possible cryopreservation.

Click here for more Embryo Freezing Information.

Click here for the Legal Aspects of Treatment.