Migration during pregnancy increases the risk of autism

The risk of being affected by autism appears to increase for children who come to Sweden in their mother's womb. Women who were pregnant when immigrating are almost twice as likely to have a child with autism. These are the results of a new study from Karolinska Institutet.

Ceilia Magnusson, PhD, Adjunct professor. Credit: Ulf Sirborn.

Text: Fredrik Hedlund. Published in Swedish in the magazine Medicinsk Vetenskap No 3/2012 (minor updates in May 2020)

It is previously known that immigrant families have a higher rate of children with autism. Researchers at Karolinska Institutet have now examined the link and revealed that the increased risk appears to be connected to whether or not the mother was pregnant when she came to Sweden.

Pregnant women who emigrate from poor countries were more than twice as likely to have a child with a low-functioning autism spectrum disorder compared to other women. These are the findings of a study published in the British Journal of Psychiatry in February this 2020.

"If the findings prove to be correct, this indicates that the occurrence of autism is linked with environmental factors, something connected to the migration process", says Cecilia Magnusson, Adjunct Professor at the Department of Global Public Health, who conducted the studies.

Half a million children

She and her colleagues have gone through records of all the almost half a million children who were in Stockholm county from 2001 to 2007. Almost five thousand children were diagnosed with autism and almost 800 of these had a foreign background. Cecilia Magnusson cannot comment on the causes behind this increase in risk, but she has some theories.

"It could be due to stress. You can imagine that fleeing from your home country while pregnant leaves you in an incredibly vulnerable position. But it can also be due to dietary factors to which you are not accustomed, or a sudden exposure to contaminants."

"A vitamin D deficiency has previously been proposed as a possible risk factor for immigrant women, but our data cannot be applied here. Women who have lived in Sweden for a long time should have even lower levels of vitamin D and thus a higher risk of giving birth to children with autism than women who recently arrived here, whereas this is not the case", says Cecilia Magnusson.