Understanding PGD

What is Preimplantation Genetic Diagnosis (PGD) and how will it help me have a healthy baby?

We all want a healthy baby, one who grows into a healthy child. Unfortunately, in some cases it’s not always how things turn out. Certain genetic conditions can cause birth defects or start to show up as a child develops and certain factors, such as knowing you have a family history of a genetic disease or being of advanced maternal age, can increase the likelihood of your baby being affected.

World leading PGD gives you a way of reducing or removing that risk.

In a standard IVF treatment, every time a cycle produces more than one embryo, a choice must be made about which embryo will be transferred. That choice is determined by the development and appearance of the embryos, usually over a five day period to work out which one has the best chance of achieving a pregnancy.

However, advances in scientific techniques mean PGD gives us another factor on which to base our decision – the genetic health of your embryo. PGD allows Fertility SA embryologists and Genea scientists to base the choice on the results of genetic tests they’ve conducted on your embryos. These tests help us to rule out embryos that contain an obvious genetic abnormality. Testing can involve either a count of the chromosomes and/or a molecular examination for a particular gene or mutation.

PGD can increase the chances of a genetically normal embryo being selected, implanting successfully and your chance of carrying and delivering a healthy baby.

If you’re considering IVF, PGD could be an important part of the equation towards you achieving your dream. Learn more about the process of PGD and what is involved.

Can we benefit from PGD?

PGD is recommended for you if you:

If you know you carry a serious genetic condition, genetic testing of your embryos before implantation is an effective and logical way to avoid 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 be unaffected.

IVF with PGD allows the couple to produce a number of embryos, but to transfer only those that are either unaffected by the condition or carriers.

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.

Two forms of PGD called Comparative Genome Hybridisation (CGH)or DNA sequencing lets us screen your embryos to find one that is genetically healthy. The good news is that our PGD results show that following the transfer of a healthy embryo, pregnancy rates among older women do not differ greatly to those achieved by women in younger age groups.

CGH can provide you with the best chance of a healthy baby, particularly when time really matters.

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 PGD as part of your treatment may be the best way to achieve your goal.

Comparative Genome Hybridization (CGH) or DNA sequencing is used by our scientists to screen your embryo to ensure it has the correct number and sequence of chromosomes in the DNA to avoid the genetic faults that could be causing it to miscarry. We then only go on to transfer genetically healthy embryos which gives you the best chance of successful implantation and pregnancy.

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 PGD.

Once again to overcome this problem, our embryologists and Genea scientists will use Comparative Genome Hybridization (CGH) to screen your embryos for chromosome abnormalities before implantation.

Only embryos that have the correct number and sequence of chromosomes will be selected for transfer to give you the best chance of successful implantation and an ongoing pregnancy.

Using PGD to select the sex of your embryo is only allowed in Australia 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 restrict the use of PGD for sex selection in Australia. (see sections 11 and 12 of the ART Guidelines).

What happens in PGD testing?

PGD testing involves carefully removing a small number of cells from an embryo for analysis. From this tiny sample, we are able to test whether an embryo has Down syndrome, cystic fibrosis, Huntington’s disease or any of a wide range of other genetic problems. Each of these conditions needs to be tested for separately and we will discuss with you what conditions need to be considered.

Most commonly, PGD is 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, our approach to PGD – biopsy at blastocyst stage improves both implantation and live birth rates when compared to the biopsy at Day 3 method 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 23 per cent of couples undertaking Day 5 biopsy on their embryo delivered a baby compared to 13 per cent of couples whose embryo was biopsied at Day 3.

Our PGD uses the latest next generation sequencing (NGS) technology.  We use it in two situations:
1. Where there is a single gene defect or chromosomal translocation that may lead to an affected child or recurrent miscarriage.
2. For screening of embryos to exclude chromosomal abnormalities (aneuploidy such as down syndrome) to ensure we replace only chromosomally normal embryos.

 

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 PGD is the right path for you.

Please do not hesitate to contact us on (08) 8100 2900 if you have any questions.