"The biggest concern for me is my son potentially having sex with a sister," mum Rachel Toyer tells 9Honey Parenting.
She's a solo mum by choice and went through IVF with donor sperm to have son Arlo, three, leading to some 'grim' concerns as he grows up.
"In Australia, the only clinic that has access to the sperm that I used is in Adelaide, five minutes from my house¡ they've created 10 families using that sperm," Toyer says.
"What that means is that my son, if we continue to live in Adelaide, is going to have at least 10 siblings created at around the same time as him."
Under current legislation, sperm donors are able to ?donate to 10 women or families in Victoria and South Australia and just five in New South Wales and Western Australia.
There is no ?legislated limit on donations in Queensland, Tasmania or the Northern Territory, however most fertility clinics set a maximum number of donations.
That means that donor-conceived children like Arlo ?can have up to five or even 10 genetic siblings depending on the state.
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It's the kind of taboo topic most parents never even have to consider, but Toyer was prepared to deal with the issue as a child of adoption herself.
"It's grim, but as an adopted person, that's always been the biggest challenge my mum raised me with," she reveals.
"You have to be aware of the fact that if you had a baby with a sibling, or a first cousin, that genetically there would be significant problems for that baby."
Growing up, she had to be careful about who she had relationships with for fear of accidentally sleeping with a relative by mistake.
In fact, Toyer once dated a step-cousin before discovering they were related.
"For a moment, I thought, 'Oh my gosh, you're an actual biological cousin'. It was scary. Fortunately, we then realised that it was a step-relation," she says.
That was over 20 years ago and Toyer is relieved her son won't have to rely on guesswork and good luck to avoid a similar awkward situation.
Now genetic testing is available and more accessible than ever before, making it much easier for Arlo to understand his own genetic identity and avoid any mishaps.
New research by Identilab reveals that about 20 per cent of Australians have turned to DNA testing in their quest to unearth their own genetic identity and that figure is rising.
This medical technology also played a huge role before Arlo was even born, as Toyer was able to 'shop' for donor sperm that was compatible with her own DNA.
It prevented her from accidentally ending up with a donor she may be related to, as well as screening for other genetic incompatibilities that could cause congenital abnormalities.
"It's so easy, when you're in a position like mine, to just make sure that's not going to happen. You just have to pay for more testing," Toyer says.
"They can cross-reference the DNA of the donor sperm with my eggs' DNA and they got rid of half of my embryos because of genetic abnormalities."?
Perinatal and congenital conditions cause about the most 80 per cent of infant deaths in Australia, a number of which can be caused by altered or 'faulty' gene or set of genes.
Many Aussies who conceive naturally are unaware of their genetic compatibility and Toyer admits she wouldn't have pursued genetic testing if she had a baby the 'old fashioned way'.
But getting that extra testing ensured her child had the best chance at life without genetic complications and was worth every dollar.
The solo mum paid about $100,000 to have her son through IVF, eating up all her savings and a portion of her superannuation by the time Arlo arrived.
"I would have paid 10 times more. I would have kept going until I ran out of super and then I would have got a loan," she says.
"I definitely thought, 'if I'm going to do it, I'm going to just go whole hog on this.'"
It was easy for her to justify the price of genetic testing when she was already spending so much on having a child, but she wants to normalise it for all Aussie parents.
That's not to say Toyer wants every Aussie to get genetic testing for themselves or their children; she just wants people to know the option exists and talk about it.
"There's a lot of stigma about bringing medicine into baby-making," she says.
"Lots of people could do genetic testing and use the medicine that we have available to improve their chances of parenthood, but there's this stigma that you shouldn't."
For some couples, genetic testing will uncover 'faulty' or incompatible genes that could affect their future children, which can help them make medical decisions.
For those going through IVF with donor eggs or sperm, it can increase the chances of a successful outcome.
And for people like Arlo and Toyer, it can give them a clearer picture of their own genetic identities.
Arlo knows that he has biological siblings out in the world and Toyer has created a photo album full of pictures of them, her IVF journey, his DNA and the donor's DNA.
It will help him down the road, both to prevent any accidental relationships with siblings, and when it's time for him to have kids of his own.
"It seems unusual for us, because that's not what we were used to, but he doesn't know any different because it's been part of his narrative since the day he was born," Toyer adds.
She's encouraging other Aussie parents to start thinking and talking about their own genetic identities, as well as those of their children if they're adopted or donor-conceived.
While genetic testing can be pricey, it was worth it for Toyer and could be helpful for other families too - they just need to know it's an option.
"If I was to go back and I had a partner, I would actually say, 'before we start making a baby, let's do a DNA test and see if we have any genetic markers that may negatively impact our child,'" Toyer says.
"To leave that all to chance just seems ridiculous to me now, but it did not seem that way when I was just a woman wanting to meet a man to have a baby."