A study by Bristol University found that mums-to-be who ate fish three times a week had children with higher verbal IQs, more advanced communication skills and better behaviour.
Omega-3 fatty acids help your unborn baby's brain, nervous system and eyes to develop healthily, particularly during the last trimester of pregnancy.
However, your body cannot make them, so they have to come from your diet.
It's thought that omega-3 fatty acids found in oily fish such as salmon, trout and mackerel are most important.
However, it's currently recommended that pregnant women eat no more than two portions a week of oily fish because of concerns about mercury.
Vegetarian diets tend to be relatively low in all omega-3s, but there are other ways to get your ration.
The Vegetarian Society recommends taking one teaspoon of flaxseed oil a day, either alone or mixed into salad dressings or smoothies.
Eating foods such as tofu, green leafy vegetables, linseed, walnuts, and other seends and nuts will also increase your intake.
Avoid supplements containing fish liver oil during pregnancy because although they are rich in omega-3, they are also high in vitamin A, which canbe harmful to your unborn child.
Columbus eggs from supermarkets are another source as the hens are fed a diet rich in flaxseed.
Scientific consultant Florence Lacroix says, 'Two Columbus eggs provides over 50% of your recommended daily allowance of omega-3s.
'Have them on two slices of a fortified bread, such as Kingsmill Head Start, with a fortified spread like Flora Pro-activ, and you'll get 100% of your daily intake.'