Study finds no evidence that maternal sickness during pregnancy causes autism

There is new evidence that a mother’s health condition during pregnancy may not be directly linked to autism in her child.

That is the conclusion of a large international research project based on extensive Danish health data, which appears to challenge the findings of several previous studies in the field.

Many earlier studies have suggested that a mother’s illness during pregnancy—such as depression—could increase the risk of autism in the child.

The theory has been, that biological mechanisms, such as elevated stress hormone levels, could affect fetal brain development.

However, the current study shows that these associations can largely be explained by shared factors in the family, like genetic factors or environmental influences.

“Our results challenge the idea that specific maternal health conditions directly lead to autism. When we account for shared genetic or environmental factors in the family, most of these associations disappear,” explains Diana Schendel, professor at the Center for Register-Based Research at Aarhus University.

By comparing siblings and analyzing fathers’ health data, the researchers demonstrated that similar associations appeared between fathers’ diagnoses and autism in their children.

Since a father’s health condition does not affect the fetus during pregnancy, this suggests that genetic or environmental factors shared in the family are linked to the risk of autism—rather than the mother’s health condition during pregnancy.

Danish registers enable precise analyses

The study is based on 1.1 million pregnancies in Denmark, and the unique Danish health registers have made it possible to track individuals throughout their lives and analyze patterns across generations.

“The Danish health registers are an invaluable resource because they cover the entire population and collect data across hospitals and medical specialties. In many other countries, health information is fragmented across different providers, making it difficult to conduct such a comprehensive analysis,” explains Diana Schendel, adding:

“The level of precision and validity we can achieve by using Danish data gives us a much better understanding of the factors that truly play a role in the development of autism.”

Fetal complications may be an early sign of autism

One of the few clear associations the researchers identified was between certain complications in the fetus and a later autism diagnosis.

These complications include issues with oxygen balance and other disruptions in fetal development.

“These complications may not be the cause autism but may instead be early signs of autism in the fetus,” says Diana Schendel.

However, she emphasizes that more research is needed to understand how these early signs can be used to better understand neurodevelopment and improve autism diagnosis and support for autistic children.

The study findings should not alter health care and health promotion practices during pregnancy. Most importantly, Diana Schendel hopes that the study can provide healthcare professionals and future parents with a better understanding of what influences the risk of autism.