Researchers have discovered that where you used to live could affect your child's chances of being autistic by up to five times.
The study looked at children whose mother had moved to the UK from outside Europe.
It showed an increased risk of autism in children whose parents had migrated from Africa, the Caribbean and Asia, the UK researchers said.
The greatest risk was for the Caribbean group, the BBC World Service reported.
Speaking on Health Check, Dr Daphne Keen, from St. George's Hospital London, said while the findings show a clear link between immigration and autism - they could not determine exactly why this was the case.
Stress factors and social isolation and so forth may operate as triggers.
The research covered 428 children diagnosed with autism during a six-year period.
"We didn't find there was an increased risk in the parents who had migrated from other European countries," Dr Keen added.
"The size of the increased risk was greatest for the Caribbean group. This was at least five times.
"The risk was also very significant, but slightly less, for the African population and much lower, but still a little present, for the Asian population."
The study took into consideration that it may just be a case of ethnicity - rather than migration - that caused the rise in cases.
However, researchers compared their results with children born of UK-born parents with Caribbean, African and Asian roots.
"We found when we analysed the two factors together, that the risk fell considerably.
"It seemed to suggest that immigration was the major factor, and ethnicity was just possibly a factor."
One theory is that the stress of migrating could act as a "trigger" for the disability, a factor discovered in similar studies looking at the causes of schizophrenia.
"There have been some interesting studies that seem to suggest that those sort of stress factors and social isolation and so forth may operate as triggers."