Autism Risk May Also Be Higher For Teen Moms, Not Just Older Couples

Could teenage pregnancy increase the risk of autism?

New findings published in the journal Molecular Psychiatry consist of the largest-ever multinational study of parental age and autism risk, funded by Autism Speak. Researchers found increased rates of autism among children whose parents had relatively large gaps between their ages, as well as teen mothers.

Previous studies have noted the link between advancing age and autism risk. However, up until this point, the findings have been relatively unclear. For instance, some have suggested that the risk increased with older dads but not always with moms.

The new study builds on the broader research of the International Collaboration for Autism Registry Epidemiology (iCARE). The goal of the new research was to determine whether advancing maternal age or paternal ages independently increased autism risk, and if so, to what extent.

For the study, researchers examined autism rates among 5,766,794 children -- including more than 30,000 with autism -- in Denmark, Israel, Norway, Sweden and Western Australia. The children were born between 1985 and 2004, and the researchers followed up on their development until 2009, checking national health records for autism diagnoses.

Researchers also identified and controlled for other age-related influences that could potentially affect autism risk. After separating for the mother's versus father's age, they also adjusted for the potential influence of the other parent's age, too.

Here are some key findings, courtesy of a news release:

• Autism rates were 66 percent higher among children born to dads over 50 years of age than among those born to dads in their 20s. Autism rates were 28 percent higher when dads were in their 40s versus 20s.

• Autism rates were 15 percent higher in children born to mothers in their 40s, compared to those born to moms in their 20s.

• Autism rates were 18 percent higher among children born to teen moms than among those born to moms in their 20s.

• Autism rates rose still higher when both parents were older, in line with what one would expect if each parent's age contributed to risk.

• Autism rates also rose with widening gaps between two parents' ages. These rates were highest when dads were between 35 and 44 and their partners were 10 or more years younger. Conversely, rates were high when moms were in their 30s and their partners were 10 or more years younger.

In conclusion, the higher risk associated with a father's old age remains due to potential genetic mutations found in sperm. On the other hand, risks related to a mother's older age remain unexplained.

"These results suggest that multiple mechanisms are contributing to the association between parental age and ASD risk," the authors concluded. 

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