Taking fish oil supplements while pregnant will not result in smarter children, according to the results of a decade-long study by Australian researchers.

Researchers from the South Australian Health and Medical Research Institute (SAHMRI) discovered that routinely taking DHA (docosahexaenoic acid) supplements - an omega-3 fatty acid found in fish oils - while pregnant does not affect the future 'brightness' of the child, despite some supplement companies claiming it will.

The team from SAHMRI followed more than 460 children from pregnancy until they were 10 years old, and found a negligible difference in the IQ of those whose mothers took fish oil supplements compared to those who didn't.

According to the research, the average IQ of children born after exposure to fish oils was 98.31 compared to 97.32 for the "control group."

Jacqueline Gould from SAHMRI told the Australian Broadcasting Corporation (ABC) there were no significant differences in language, academic abilities, or executive functioning as a result of fish oil exposure.

"Overall we found that there's been no benefit ... so the babies in this study don't seem to have any benefit to their brain development from their mothers taking fish oil," Gould said on Wednesday.

"Mainly we looked at their intelligence. So at 18 months we did some assessments with them, and again when they reached four years and just now when they turned seven."

She said the study was undertaken in response to claims from some manufacturers that taking the supplements would lead to happier, healthier and smarter babies.

"Back when we first started this study some of the supplement manufacturers were specifically marketing their supplements as being beneficial for babies' brain development," she said.

Gould added that while there was no tangible difference in the IQ of kids exposed to fish oil's benefits, it did result in more full-term pregnancies.

"The length of pregnancy increased just a little bit in the fish oil group, and that actually meant there were slightly fewer babies born very pre-term," Gould told the ABC.

"We still have to do more work to find out whether or not this is a true effect of the fish oil, but that would be quite a significant benefit if it is."