Genetic Testing: The What and the Why

Discovering you have a genetically inherited condition in your family generates a raft of questions and fears. Getting good information is key to understanding and planning for the future.

There are many places and websites that can help… from support groups where people can pass on their knowledge and experience, through to medical services that offer diagnosis and informed counselling.

Diagnosis Before Birth and Prenatal Testing

Antenatal screening and diagnostic tests are available in New Zealand to predict risk factors and diagnose abnormalities.

These tests are optional, and factors like age can automatically put you into a risk category.

If your results do come back ‘high risk’ (usually greater than 1 in 300) then you will be offered more accurate tests. For many couples this can be a difficult choice to make, and consulting your lead maternity carer will be helpful. Remember, it is your choice whether to have the tests, and you should be offered thorough counselling before you make your decision.

Things to consider in choosing further testing:

  • Some intervention may be possible to treat the condition before or at birth.
  • The test may reveal that your foetus is unaffected, and reduce anxiety during the pregnancy.
  • If the test results show the disorder is present and you decide to continue with the pregnancy, it will give you time to prepare yourself and others for a baby that may be different and have extra needs.
  • If you know what to expect you can get advice from support groups.
  • If the test shows the disorder is present, you may choose not to continue with the pregnancy.

Pre-implantation Genetic Diagnosis... what is it and who can have it?

Pre-implantation Genetic Diagnosis (PGD) is an in vitro (IVF) screening process used to test embryos for serious inherited genetic conditions and chromosomal abnormalities before pregnancy.

Once an embryo is created through IVF, one or two cells are removed from it and tested for the specific genetic conditions or chromosomal disorders. Unaffected embryos can then be transferred into the woman’s uterus or frozen for later implantation.
 Some inherited conditions that can be tested for:

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

Chromosomal abnormalities that can be tested include:

  • Translocations
  • Aneuploidy (chromosome additions or deletions)

In New Zealand PGD is permitted for serious conditions where a child has at least a 1 in 4 chance of inheriting the condition, or chromosome abnormalities associated with recurrent miscarriage or advanced maternal age. Up to two cycles of IVF can be publicly funded for PGD.

Useful websites:

Diagnosis at birth or soon after

Often a diagnosis of a condition is made shortly after birth. That’s hard when it is both unexpected and it also seems you’re surrounded by other parents, with strong and healthy babies.

There should be a strong medical support team that will have access to counsellors, but parents often say the biggest source of emotional support comes from other parents or support groups in a similar situation who can offer positive messages and advice.

You should be given clear information about your child's condition and his or her care. If you are not sure, ask for more information. For ongoing and complex conditions there should be a structured support team with a key worker to co-ordinate your child's health and disability needs.

Many disorders may appear slowly, with symptoms that can be hard to attribute to any one cause. However, if you’re concerned, your first port of call is your doctor or Plunket nurse. You will then be referred to a paediatrician through the public system, or choose to see a paediatrician privately.

At this point you may also be referred to the Genetic Health Service. The Genetic Health Service has three hubs across the country; Auckland, Wellington and Christchurch. They offer diagnosis information and counselling by medical specialists.

The New Zealand Organisation for Rare Disorders is a good starting point for information about a range of conditions.

Self Help Organisations United Together brings together self help groups to share resources and information.

Some conditions do not appear until teenage or adult years. Usually though, families will have advance knowledge through symptoms or routine medical conditions. That gives valuable time to adjust and prepare for the future.

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