How early would you think a person could be diagnosed with autism? At the moment, the very earliest someone is likely to get a diagnosis is around 18 months old. Before that, babies are all kind of the same when it comes to communication and social interaction (which is to say, they all suck at it), making it difficult to judge which ones are better or worse at things like interpreting verbal and non-verbal language. And since there’s no physical test that can show us the presence of autism any earlier than that, there’s – wait, what?

A brain scan might be able to show us the presence of autism before birth?

A new study, being presented at this year’s American Association for Anatomy annual meeting, during the Experimental Biology 2022 meeting, has found significant differences in brain structures of people with autism compared to those without. But even more amazing is that these differences were noticeable as early as 25 weeks gestation – or to put it another way: more than three months before birth. The discovery offers potential for earlier diagnosis for people with autism.

“Given that many genetic and environmental factors could affect the emergence of [autism spectrum disorder] starting in the fetal stages, it is ideal to identify the earliest signature of brain abnormalities in prospective autism patients,” said Alpen Ortug, first author of the study and a postdoctoral research fellow at Athinoula A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Harvard Medical School.

“To the best of our knowledge, this is the first attempt to semi-automatically segment the brain regions in the prenatal stage in patients who are diagnosed with autism later and compare different groups of controls,” Ortug said.

Autism spectrum disorder, or ASD, affects around one in every 68 children in the US, and despite what you may have read on Facebook, we really don’t know why. Most likely, though, is that it’s caused by a combination of things: “Both genetic and environmental factors during prenatal and postnatal development are believed to account for the emergence of ASD,” notes the study abstract.

But if it’s partially genetic, the team reasoned, then perhaps they could find signs of the condition turning up during fetal development. They analyzed 39 MRI scans taken of living fetuses at around 25 weeks gestation – the scans had already been taken regardless of the study, not specifically for it – to see if they could spot any differences in brain structure between children who would go on to develop autism and children who wouldn't.

“It is critical to be aware of an altered initial brain anatomy in ASD for better predicting what aspects of brain function will likely preferentially and precociously deteriorate,” the team explain.

Knowing in advance which kids show signs of autism “would allow for potentially earlier/better prevention and treatment,” they added.

Their hunch paid off: the scans of fetuses that went on to receive an ASD diagnosis showed significant differences in an area of the brain known as the insular lobe. That’s a region responsible for things like self-awareness (both physical and emotional), social abilities, and behavior regulation – all things people with ASD can have real trouble with.

“Our results suggest that an increased volume of the insular lobe may be a strong prenatal MRI biomarker that could predict the emergence of ASD later in life,” explained Ortug.

Scans from children with ASD also showed an enlarged amygdala and hippocampal commissure.

These findings could be really good news for some people with ASD. As the name suggests, it’s a spectrum disorder – much worse for some people than others – but with early intervention, many people with autism can learn strategies and skills that help them navigate the world in ways neurotypical people often take for granted.

“Earlier detection [of autism spectrum disorder] means better treatment,” Ortug said.