Too little — or too much — of certain substances during pregnancy may increase the odds of having a child with autism. Here we explain what scientists know about these associations.

Genes influence how autistic people react to sights, sounds and other sensory cues, whereas environmental factors shape their tendency to notice and seek out such stimuli, a new study in twins suggests.

A typically protective stress response could help to explain the connection between maternal illness and neurodevelopmental conditions.

Autism and other neurodevelopmental conditions are more common among children born by C-section than those delivered vaginally, but the procedure itself does not underlie the association, according to a new study.

Newborns with either above- or below-average levels of an immune-system marker, among other differences, have increased odds of being autistic.

Women who use marijuana while pregnant may be more likely to give birth to an autistic child. But investigators call for a cautious interpretation of the results.

Brothers and sisters of people with autism are both about two to three times more likely than the general population to have an autistic child themselves.

The relative contributions of genetic and environmental factors to autism have held steady over multiple decades, according to a large twin study.

High blood pressure during pregnancy may raise a woman’s chances of having an autistic child.

A study that followed 126 autistic people in England from their preteen years to age 23 found little improvement in their behavioral and emotional problems.