WA scientists are challenging the myth that inbreeding always leads to unhealthy babies.
The highly contentious, often-tabooed practice has in the past been linked to deformities such as heart disease, mental retardation, deafness and even blindness.
Australian research published in 2001 showed that babies born to first-cousins are nearly three times more likely to have serious birth defects.
But Professor Alan Bittles, an adjunct professor at the Centre for Comparative Genomics at Murdoch University, who has spent 30 years researching the topic says most children born to first-cousins are healthy.
In WA, about 500 marriages are between first-cousins.