Understanding Preimplantation Genetic Diagnosis

Known genetic conditions

If you know you carry a serious genetic condition, genetic testing of your embryos before implantation is an effective and logical way to reduce the chances of passing that condition onto your future children.

For example, when two cystic fibrosis carriers conceive a child, there is a 25 per cent chance that the baby will have cystic fibrosis, a 50 per cent chance that the baby will be a carrier and a 25 per cent chance that the baby will not carry either parent mutation. IVF with PGD allows the couple to produce a number of embryos, and to transfer only those that are unaffected by the condition.

Genea has developed the largest range of tests in Australia – so far, for more than 200 inherited diseases.

Advanced maternal age

It’s an unfortunate fact of reproductive science that the frequency of chromosomal abnormalities - that’s when your embryo is missing a chromosome or carrying an extra one -  increases with maternal age. These chromosomal abnormalities can cause your embryo to fail to implant or miscarry or they might result in a baby born with developmental problems or a serious genetic condition such as Down Syndrome.

Our Scientists use a form of PGS called Next Generation Sequencing (NGS) to screen your embryos in order to find those that have a balanced chromosome set and are therefore genetically healthy. The good news is that our PGS results show that following the transfer of a genetically healthy embryo, pregnancy rates among older women do not differ greatly to those achieved by women in younger age groups. 

Recurrent miscarriage

Random chromosome problems are thought to be the cause of the majority of miscarriages – what happens is that a genetically abnormal embryo implants in the uterus, but is destined to fail. Unfortunately miscarriages are not uncommon with approximately one in five pregnancies ending in a miscarriage. However, due to advanced maternal age or a number of other possible factors, some women are more prone to miscarriage. If you’ve experienced multiple miscarriages, considering PGS as part of your treatment may be the best way to achieve your goal.

A DNA sequence-based method (Next Generation Sequencing or NGS) is used by our Scientists to screen your embryo to ensure it has the correct number of chromosomes and to avoid some of the genetic faults that could cause it to miscarry. We then go on to transfer only balanced embryos.

Multiple failed embryo transfers

Perhaps the problem you’re facing is that your IVF cycles are not working because your embryo fails to implant after the transfer. If this has happened a couple of times, your Fertility Specialist may recommend PGS.

Once again, to identify possible chromosome problems, Genea Scientists will use one of our complete chromosome screening processes to test your embryos for chromosome abnormalities before implantation. Only embryos that have the correct number of chromosomes will be selected for transfer.

Prevent transmission of sex-linked genetic disease

Using PGD to select the sex of your embryo is only performed if the testing is being used to avoid passing on a specific sex-linked genetic disorder to a child.

The National Health and Medical Research Council’s Assisted Reproductive Technology Guidelines outline specific situations for the use of PGD for sex selection in Australia. (see sections 11 and 12 of the ART Guidelines).

For more information on this please contact us.

Genea was the first clinic in the world to successfully introduce Preimplantation Genetic Diagnosis (PGD) for Day 5 embryos in 1999, achieving the first baby ever born using this technique. A review of information from the Australian and New Zealand Assisted Reproduction Database (ANZARD) from 2004 to 2008 showed blastocyst biopsy for PGD improves both implantation and live birth rates when compared to biopsy at Day 3. The review showed clinical pregnancy rates from Day 5/6 biopsies were nearly double at 29 per cent compared to 17 per cent for Day 3 biopsies with 23 per cent of couples undertaking Day 5 biopsy on their embryo delivering a baby compared to 13 per cent of couples whose embryo was biopsied at Day 3.

More than 2,000 single gene disorders have been identified and we are capable of building a test for nearly any one of them. To date, we’ve been asked to test for approximately 230 disorders, more than any other clinic, and we’ve developed customised specific tests for each one, including some very rare disorders.

In 2012, an Australian IVF clinic stated that the holy grail for IVF technology would be the ability to test every one of the 23 chromosome pairs in the embryo before implantation. At Genea we have been doing just that since November 2009.

Genea was one of the first clinics in the world to adopt the technique of microarray Comparative Genome Hybridization (CGH) or microarray CGH, we’ve offered it to our patients since 2009. While standard chromosome tests can only detect some of these conditions, the CGH test can identify very small changes in all 23 chromosome pairs that standard tests are not able to detect. Genea is now able to offer an alternative to CGH - Next Generation Sequencing (NGS) - which is a newer technology based on genome sequencing, and is capable of determining chromosome balance using more information at the genome level than ever before.

Genea is one of the very few centres in Australia with the vital combination of world class IVF and genetics facilities to perform these sophisticated tests successfully. 

Please do not hesitate to contact one of Genea's PGD scientists on 1300 652 687 should you have any questions.

Chromosome abnormalities can include having the wrong number of chromosomes, or having chromosomes that are not completely intact. The most common chromosome abnormality is called aneuploidy which is having either too few chromosomes (e.g. Turner syndrome with only a single X chromosome) or too many chromosomes (e.g. Down syndrome with 3 copies of chromosome 21).

Other chromosome abnormalities or imbalances can involve genetic material either added to a chromosome (a duplication) or missing from a chromosome (a deletion). If these imbalances are very small, then they are called microduplications or microdeletions.

Chromosome abnormalities increase the risk of miscarriage or physical and intellectual disabilities. Children born with chromosome abnormalities may have altered facial and physical features, be slow to reach developmental milestones, mental retardation and other serious health issues.

PGD and PGS involves carefully removing a small number of cells from an embryo for analysis. From this tiny sample, Genea is able to test whether an embryo has Down syndrome, or any of a wide range of other previously identified familial genetic problems. These conditions typically need to be tested for separately and we will discuss with you what conditions and tests need to be considered.

Specialised PGD is most commonly used where a couple is aware of the possibility that their offspring will inherit a genetic disease. Even though they may not have a problem with infertility, the couple undergoes a stimulated IVF cycle with the aim of producing a number of embryos. Genetic material from these embryos is tested to see which, if any, of the embryos carries the genetic disease, and only embryos that do not show the disease are transferred to the woman’s uterus.

As we mentioned above, Genea’s leading approach involving biopsy at blastocyst stage results in both higher implantation rate and live birth rates when compared to the biopsy at Day 3 method still used by many other Australian clinics.

A review of information from the Australian and New Zealand Assisted Reproduction Database (ANZARD) from 2004 to 2008 showed nearly twice as many couples undertaking Day 5 biopsy on their embryo delivered a baby compared to couples whose embryo was biopsied at Day 3.

Genea uses two major types of tests or analysis:

• Total Chromosome Analysis; and
• Polymerase Chain Reaction (PCR);
• Combination Polymerase Chain Reaction (Total Chromosome Analysis / PCR)

If you have or carry a diagnosed genetic problem or have suffered three or more miscarriages in a row, you can call us to discuss whether one of the above approaches is the right path for you. Genea is one of the very few centres in Australia with the vital combination of IVF and genetics facilities to perform these sophisticated tests successfully.

Please do not hesitate to contact one of Genea's PGD scientists on 1300 652 687 should you have any questions.

All Genea's Fertility Specialists have undertaken specialist study and training to understand the different factors which might be impacting your fertility. They'll take the time to diagnose your condition, provide you with a range of options and work with you to devise the best treatment plan - just for you.

Genea Specialists