Population-based screening for cystic fibrosis involves pregnant women being tested to determine if they are carriers of one of the 2000 or more cystic fibrosis (CF) genes.
If they do have one of these genes, then their partner is tested to establish if he is also a carrier of one of these genes. If both parents have a CF gene then they will be offered diagnostic tests on their unborn baby to see if the child may have cystic fibrosis.
Cystic fibrosis only occurs when both parents have CF genes and this happens in rare cases. If both parents do have the gene it doesn’t necessarily mean their baby will have cystic fibrosis – this is only one of the possibilities. The other possibilities are that the child will be born a carrier of CF like their parents (but not have the condition), or they will be born without cystic fibrosis and will not be a carrier either.
If the embryo does have cystic fibrosis, parents can decided if they would like to proceed with the pregnancy. If the baby is a carrier it can be helpful for them to know this as they are growing up and can ask for their future partner to be tested to see if they are also a carrier of a CF gene before deciding to start a family.
For future pregnancies, couples who are both carriers of CF have the option of having IVF and the embryos tested for cystic fibrosis before they are implanted in the mother’s womb. This is called prenatal diagnosis (PND) or pre-implantation genetic diagnosis (PGD).
In the Australian state of Victoria, population-based screening for CF carriers is offered to pregnant women although not all decide to take up this offer. Screening does not rule out the possibility of having a child with CF if one of the parents is a carrier of a specific CF gene that is not routinely tested for.
In Australia, one study found 67 percent of parents who were both identified as carriers through their screening programme decided to use prenatal diagnosis when having more children.
A study of 71 CF health professionals in Australia found there was moderate support for population CF carrier screening. Support was linked to parents getting reassurance when they are not carriers and the importance of the daily treatment programme for people with CF. Opposition was associated with fear of discrimination against carriers and limitations with predicting clinical outcomes. Some people with cystic fibrosis are not born with serious forms of the condition.
There is no population-based CF screening programme in New Zealand. A large majority of children with CF are born to parents who did not know they were carriers and only find out after the birth of their baby. Prenatal genetic testing can now be sought through some private fertility clinics. Free carrier testing is available through Genetic Health Services if there is a strong family history of the condition.
Cystic Fibrosis Victoria’s Position Statement on carrier screening supports individuals having an opportunity to make informed life and reproductive choices as a result of carrier screening.
Cystic Fibrosis New Zealand recommends people interested in understanding their risks of being a carrier for a CF gene to contact the Genetic Health Service.
Genetic Health Service contact numbers:
Genetic Health Service – Northern Hub
Toll Free: 0800 476 123
Genetic Health Service – Central Hub
Toll free: 0508 364 436
Genetic Health Service – South Island Hub
Toll free: 0508 364 436