Concerns that eating fish while pregnant could potentially harm unborn babies by unnecessarily exposing them to mercury could be unfounded, experts in Northern Ireland have claimed.
For years, women have been told to avoid eating certain fish during pregnancy because of concerns over mercury.
Almost all fish and shellfish have traces of mercury.
But long-term research suggests that eating a diet rich in fish may not be as dangerous as previously thought.
The project, which has been running since the 1980s, involved 1,500 mothers and their children in the Seychelles.
The area was chosen due to the high level of fish inhabitants consume - up to 12 servings a week, which is 10 times greater than people in Europe and America.
When children were 20 months old they underwent a series of tests designed to measure their communication skills, behaviour and motor skills.
Researchers also collected hair samples from pregnant women to test mercury levels and analyse polyunsaturated fatty acids in their bodies.
The study, which was carried out by the University of Ulster and the University of Rochester Medical Centre in New York, found there was no link between mercury exposure in the womb and lower test scores as toddlers.
In fact the team actually discovered that children whose mothers had a high level of omega 3 - which is found in fish - performed well in the tests.
It is believed that when large amounts of mercury accumulate in the body, they can cause reproductive problems and nervous system disorders. "The findings indicate that the type of fatty acids a mother consumes before and during pregnancy may make a difference in terms of their child's future neurological development," said Sean Strain, a professor of human nutrition at the University of Ulster and lead author of the study.
Philip Davidson, the principal investigator of the Seychelles Child Development Study, told the Sunday Times: "It appears that the relationship between fish nutrients and mercury may be far more complex than previously appreciated.
"These findings indicate that there may be an optimal balance between the different inflammatory properties of fatty acids that promote foetal development and that these mechanisms warrant further study."
The Food Standards Agency advises that pregnant women should eat one or two portions of oily fish a week. But they warn against eating certain types of fish, such as shark and marlin - or lots of tuna - because of the risks to the developing foetus associated with mercury.
In the UK, pregnant women have been advised not to eat more than two tuna steaks a week (weighing about 140g cooked or 170g raw) or four medium-size cans of tuna a week (with a drained weight of about 140g per can) because of the levels of mercury.
The project also involved the Seychelles' health and education ministries and the findings were published in the American Journal of Clinical Nutrition this month.
Good: the Government previously advised women to avoid eating them if there was a history of allergy such as asthma in their child's immediate family. This has now been changed - research has shown no clear evidence they affect the baby developing a peanut allergy.
Good: you can enjoy a coffee, but the NHS recommends a limit of 200mg a day of caffeine, the equivalent of two mugs of instant coffee.
Soft cheeses with white rinds
Bad: don't eat mould-ripened soft cheese such as Brie and Camembert.
Bad: always eat cooked rather than raw shellfish. This including mussels, lobster and crab as they can contain harmful bacteria and viruses that can cause food poisoning.
Unclear: experts still aren't sure about the precise amount of alcohol that is safe to drink in pregnancy, but they do know that drinking even moderate amounts can be harmful. NHS guidance states: "Women who are pregnant or trying to conceive should avoid alcohol altogether".