Over the past thirty years occasional studies have pointed to an increased frequency of autism in the children of immigrant parents but the factors that might lie behind this are complicated and there has been relatively little research into this issue. Daphne Keen from St George's Hospital in London led a team studying 428 children with autism who had been treated, over a six-year period, by child development services in South-West London. They found that mothers born outside Europe had a significantly higher risk of having a child with autism-spectrum disorder. Mothers from the Caribbean had the highest risk and mothers of Black ethnicity had a significantly higher risk compared to White mothers. However, a statistical analysis of the results showed that most of the increased risk was due to immigration rather than ethnicity.
Keen, D.V., Reid, F.D. and Arnone, D. - Autism, ethnicity and maternal immigration British Journal of Psychiatry April 2010, 196(4), 274-281