By JENNY HOPE

Last updated at 00:01 16 February 2007

Pregnant women who do not eat fish regularly could be harming their baby's development, doctors have warned.

Those who eat fish three times a week have brighter and better behaved children, say researchers.

Their study, published in The Lancet, concludes that women should be eating at least 12ozs (350g) of fish and seafood a week.

But the researchers, from Bristol University, expressed concern that recent advice about what women should eat in pregnancy may be deterring them from eating fish.

The Food Standards Agency has advised mothers-to-be to eat no more than two portions of oily fish a week. It said they can eat any amount of white fish, except shark and marlin.

The advice follows concerns about the food's mercury content, which it is claimed could harm a baby's nervous system, and concerns over pollutants in oily fish. Oily fish such as salmon, mackerel,

herring and trout contain the most omega 3 fatty acids, which play an important role in helping the brain grow.

Professor Jean Golding from Bristol University said: 'Eating fish, particularly oily fish, is important for a child's development in the womb but the message has been overshadowed by warnings about possible risks.

'However, there is no evidence that small amounts of mercury have an adverse effect on the brain.

'If there was an adverse effect then we would have seen it in our study, rather than the big benefits gained from fish consumption in pregnancy.' Some 9,000 families took part in the study, which compared the amount of fish eaten by pregnant mothers with the development and behaviour of their offspring up to age eight.

Mothers who ate more than 12ozs of seafood a week had children who were more advanced in development tests measuring motor, communication and social skills, were better behaved, and had better verbal IQ scores.

The children whose mothers had eaten little or no fish were 28 per cent more likely to have poor communication skills at 18 months and 35 per cent more likely to have poor coordination as toddlers. The risk of bad behaviour and low verbal IQ at the age of eight was almost 50 per cent higher in children whose mothers avoided fish.

A study of fish oils in December showed they help boost babies' brainpower, coordination and vocabulary.

Sue Macdonald of the Royal College of Midwives said women should be aware of the benefits of eating fish.

But she added: 'The research does present a dilemma in achieving a balance between eating sufficient fish, especially oily fish, to be of benefit against the negative effects of increasing the intake above recommended levels in terms of potential toxic effects.

'I would advise women to talk to their midwife, who can give realistic advice.'