Navigating pregnancy and genetic tests

While testing for Down syndrome has been a feature of pregnancy screening for decades, new research by the Murdoch Children’s Research Institute shows that risk for conditions like cystic fibrosis, Fragile X syndrome and Spinal Muscular Atrophy (SMA) is comparable to the genetic risks for Down syndrome.

In a study involving 12,000 women, one in twenty people tested were found to be carriers of one of the three above mentioned conditions. But if you think that family history is an indicator, you’d be wrong: 88 per cent of carriers had no family history of the condition.

So why doesn’t anyone know about these genetic tests? To a large degree the low level of awareness is due to the fact that, until recently, doctors restricted these discussions to families where there was a family history of the condition.

New practice guidelines from the Royal Australian and New Zealand College of Obstetrics and Gynaecology (RANZCOG) released this year (2018) now recommend discussing the availability of genetic screening with all prospective parents.

While testing for conditions like Down syndrome and the more common inherited disorders such as SMA, Fragile X and Cystic Fibrosis are well established, the advances in genetic technology mean that it’s now easier to test for hundreds of less prevalent disorders, potentially creating a slippery slope where it’s difficult to draw the line on what constitutes a serious enough condition for investigation or intervention.

And with more screening comes the potential for greater economic and human resource costs to the health system.

Dr Melody Caramins, Chair of the Royal College of Pathologists of Australasia’s (RCPA) Genetics Advisory Committee, states it’s an issue that needs addressing as new genetic technology comes onboard:

“It’s an important question, which is why the RCPA is currently preparing an application for funding of basic carrier screening to be considered for inclusion on the Medicare Benefits Schedule.

“Obviously, the more information that can be provided to a parent about the risks of conditions developing, the more power they have to make decisions,” says Dr Caramins.

“Couples where both parents are carriers of cystic fibrosis or spinal muscular atrophy have a one in four chance of passing that condition onto a child.”

For those interested in being tested, the carrier screening test for cystic fibrosis, Fragile X syndrome and SMA is not covered by Medicare. It’s available through a number of pathology and testing providers and costs $345-400. In Australia, it is widely available in all states and territories.

Expanded preconception (or pre-pregnancy) screening sifts through a person’s genes to evaluate their carrier status for hundreds of conditions, by looking at DNA mutations and recessive genes, and is available through a number of Australian providers and can be valuable.

For example, the recessive brain condition, Tay-Sachs disease, was prevalent amongst Ashkenazi Jews but after screening was introduced in the 1970s, incidence of the condition dropped by 90%. In Mediterranean countries thalassaemia has been greatly reduced by pre-pregnancy screening.

But while screening can help identify risks, that doesn’t mean a baby will definitely manifest the condition. It should also be noted that some conditions can develop in the womb.

“It’s a lot of information to absorb and to consider,” says Dr Caramins “Patients thinking about availing themselves of the service are recommended to have genetic counselling.”