The study found that women who took much linoleic acid in their diet - a type of omega-6 fatty acid found in vegetable oils, nuts and seeds - had a 34% lower chance of giving birth to a child with autism compared to women who consumed low levels of this nutrient.
In addition, women with a diet low in omega-3 fatty acids, mainly present in fish, they had a 53% greater chance of having a child with autism compared to women who ate fish regularly.
The study shows only an association, not a cause-effect relationship between the consumption of fatty acids in pregnant women and a lower risk of giving birth to a child with autism. Furthermore, the study involved few women so further research will be needed to confirm the results.
According to the researchers, the reason for this association is unknown, it has been shown that this type of fatty acids are very important for fetal brain development. The fatty acid supply is used by the fetus toward the end of pregnancy, and is required for the first two months of life.
It is recommended that pregnant women take about 200 milligrams of docosahexaenoic acid (DHA) per day.
The researchers found that eating high amounts of omega-3 fatty acids did not reduce further the risk of autism compared to women taking average quantities. This means that the deficit of omega-3 fatty acids during pregnancy may increase the risk of autism, but the excess does not provide extra benefit.
The researchers took into account other factors that might influence the risk of autism, such as maternal age, total calorie intake and consumption of snuff during pregnancy but it is possible that other factors not included in the study could explain these results.
Kristen Lyall, Kassandra L. Munger, Éilis J. O'Reilly, Susan L. Santangelo y Alberto Ascherio. Maternal Dietary Fat Intake in Association With Autism Spectrum Disorders. American Journal of Epidemiology, 27 Junio 2013.