If you have a set of twins in the family, you’ll be no doubt shocked to hear that around one third of twins are incorrectly classified as fraternal when they’re actually identical and vice versa. Here’s why it matters…
New research indicates that about 30 per cent of twins are being classified incorrectly, and parents are turning to DNA tests to double check results.
A study by the Australian Twin Registry, and the Murdoch Childrens Research Institute found that 32 percent of parents of identical junior twins were unsure or incorrect about their twins’ genetic identity.
“Some people believe that to be identical you have to look identical and behave identical, and if you’re not then you must be fraternal, that’s wrong. You can get identical twins that look and behave quite differently,” Dr Jeff Craig, of Melbourne University’s Australian Twin Registry, tells SBS.
“The second assumption starts in the womb, when there’s two placentas. You cannot say those are identical or fraternal, they can be either.”
Doctors told Sue Sukkel that her daughters, Abbie and Lilly, were fraternal – which means they’re genetically distinct. But Ms Sukkel tells SBS that the girls grew to look similar. She says, “When they were born, I constantly got stopped in the street, constant questions.”
Three years ago she decided to have the girls DNA-tested, and the results revealed they are indeed identical.
“When I got the letter saying they were identical, it was so overwhelming that I burst into tears, because all of a sudden everything made sense,” Ms Sukkel says.
So why is it so important to know whether twins are fraternal or identical? Researchers say it’s important to know for mental and physical health reasons. Dr Jeff Craig says identical twins can share some medical issues, like autism.
“If one of [the twins] develops a disease and they’re identical, the other one should be screened for that disease as they’re more likely to have it. In some cases it can be a life or death situation.”
But there are also positives.
“If one of them needs a transplant, the other is probably a perfect match. One of our twins said, ‘Well now I know where I can go if I need a spare kidney’.”
The Australian Twin Registry lists a plethora of reasons why it’s important to know your twins’ correct genetic classification:
- Implications for the bonding of twins,
- Tissue compatibility in organ transplantation,
- Assessing disease risk,
- The personal right to know your identity,
- Legal and educational reasons,
- Estimating the likelihood of the mother or close relatives giving birth to further sets of twins,
- And to avoid embarrassment when asked by family, friends and strangers.
If you’re the parent of a set of twins, do you agree with the results of their genetic testing? Or would you resort to double checking with a DNA test?