"There are so many trials where pregnant women are supplemented with omega-3 fatty acids and they've all got different results," said lead study author Jacqueline Gould, a researcher at the Women's and Children's Health Research Institute in Adelaide, Australia. "We found that there was neither a positive nor a negative effect on visual or neurological outcomes."
The Australian team, who published their findings in The American Journal of Clinical Nutrition, analyzed data from 11 clinical trials with a total of 5,272 participants who were randomly assigned to take omega-3 supplements or placebos during the last half of their pregnancies.
Across the trials, the amount of omega-3 taken by the mothers ranged from 240 to 3,300 milligrams per day. And the ages at which children's brain and vision development were assessed ranged from newborn to 7 years old.
According to the researchers, most of the clinical trials included too few participants to distinguish subtle differences expected from nutritional studies, excluded complicated pregnancies (in which greater differences might have been seen) and didn't follow the children long enough during development.
"Our analysis highlights that more research is needed," Gould told Reuters Health.
Omega-3 fatty acids are crucial for healthy fetal brain development and are commonly found in fatty fish such as tuna, mackerel and sardines. Human brains and eyes contain large amounts of docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA), both forms of omega-3.
Developing fetuses can get DHA from their mothers' fat stores, and from food and supplements they consume during pregnancy.
Image: Omega 3 supplements, via Shutterstock