The 'Children of the 90s' study has followed 14,000 children from development in the womb through to their early teens. It has already reported a strong positive link between oily fish intake during pregnancy leads to children with better language and communication skills.
While the study focuses on wider-reaching aspects of child nutrition, the link between eating oily fish for more intelligent babies has attracted the most media interest.
Previous studies have linked increased intake of omega-3 fatty acids with lower rates of post-natal depression, and also better-behaved children.
The new funding from the Wellcome Trust and the Medical Research Council (MRC) will enable the researchers to continue to follow the children through their teens.
Director Professor George Davey-Smith said: "It is a clear recognition of the importance of the project to scientific research today. We will create a resource which will enable scientists to understand so much more about the causes of ill health, chronic disease and impaired development - and eventually do something to reduce the burdens of common disease."
The results from the omega-3 study were presented at a meeting organized by the Institute of Brain Chemistry and Human Nutrition earlier this month and reported in the Economist.
Data from the study was analysed by Joseph Hibbeln at the US National Institute of Health and showed that the children of mothers who had the highest intake of omega-3 during pregnancy were better at making friends and had better social skills.
More importantly, the researchers reported that children of mothers who had very low oily fish intake during pregnancy had lower IQs when tested verbally.
The results have implications for public health policy where expectant mothers are currently advised against too much oily fish intake due to fears of contaminants like methyl mercury. The new data suggests that the benefits might outweigh the risks.
A possible solution is to use omega-3 supplements or eat other omega-3 fortified foods.
The study has also drawn attention to the difference between omega-3 and omega-6 fatty acids. A recent report from British charity Sustain reported that current omega-6 intake from soy and evening primrose oil, for example, is much bigger than 50 years ago.
Docosahexaenioc acid (DHA), one of the main omega-3 fatty acids, is thought to be involved in the membrane of ion channels in the brain, making it easier for them to change shape and transit electrical signals. In the absence of DHA, the brain uses omega-6 fatty acids, which have been proposed to be less efficient.