Studying children with autism and their parents, researchers have found that when a child has autism, his or her parents are more likely to have autistic traits than parents who don't have a child with an autism spectrum disorder
The related research can be found here : Lyall et al 2014 - Parental Social Responsiveness and Risk of Autism Spectrum Disorder in Offspring
Listen to a BBC Radio 4 show on autism here: 7 March 2011 - BBC Radio 4 - Steep Rise in Autism
The Social Responsiveness Scale (SRS) was used to measure the presence of autistic traits.
When both parents had mild elevations in SRS scores, the study indicated that they were 85 percent more likely than parents without elevated scores to have a child with an autism spectrum disorder. If only one parent's SRS score was high, the likelihood of having a child with autism spectrum disorder increased by 53 percent. And even among children without autism diagnoses, elevated parent scores correlated with higher SRS scores in their children.