Frequently asked questions
The two major types of inheritance that can lead to a healthy couple having children with serious genetic conditions are called autosomal recessive and X-linked recessive.
- In autosomal recessive inheritance, a person only develops the disease if they inherit the same faulty gene from each parent. if a person has one faulty gene and one healthy gene, they will not have the condition. They are a so-called “carrier” of the condition. If both members of a couple are carriers of the same faulty gene there is a 1 in 4 chance of having a child affected by that condition. The most common types of autosomal recessive conditions in our community are thalassemia and cystic fibrosis.
- X-linked inheritance occurs when the faulty gene is on the X chromosome. Males have an X and a Y chromosome whilst females have two X chromosomes. When there is a faulty gene on the X chromosome, females are generally unaffected or more mildly affected than males since they have a second normal copy of the gene. Males only have one X chromosome, so if there is a faulty gene on their X chromosome they are more severely affected by the condition since they do not have a second normal X chromosome to compensate. If a woman is a carrier for an X-linked condition, there is a 1 in 4 chance of having an affected son with each pregnancy. The most common X-linked recessive condition is fragile X syndrome.
If you or or partner have a relative with a genetic condition, you may be at increased risk of having a child with a genetic condition. Examples of inherited genetic diseases include thalassemia, cystic fibrosis, fragile X syndrome, spinal muscular atrophy, and haemophilia. Some ethnic groups are at increased risk of specific genetic conditions. If you a relative with a genetic condition, you should discuss this with your GP. Your GP can refer you to a genetic counsellor or medical geneticist for further advice and testing if needed.
A healthy couple can still pass on genetic changes to their child without a family history of an affected relative. This is because there is a small risk that a couple are healthy "carriers" for the same condition. Genetic carrier testing for couples without a family history of an affected relative is not usually covered by Medicare or a public hospital and are optional. The cost of testing for three of the most common genetic conditions - cystic fibrosis, spinal muscular atrophy, and fragile X syndrome - is currently between $250-$300. Carrier screening can be performed at any time, but it is preferable to screen before a couple conceives so that they have time to understand and consider their reproductive options.
If you and your partner are carriers of the same genetic condition, then you should seek genetic counselling prior to getting pregnant. This will give you time to consider all the options available to you, including:
- Getting pregnant naturally and having the baby tested after birth
- Having IVF and preimplantation genetic diagnosis in order to selected unaffected embryos to get pregnant
- Getting pregnant naturally and having diagnostic testing during pregnancy to see if the baby will be affected
- Using IVF and donor sperm or eggs from donors who are not carriers of the condition
- Not to have children at all