THOUSANDS of people in Dorset could be unknowingly walking around with brain damage because their mothers drank alcohol during pregnancy.

Dr Nick Moffat, a Dorset clinical psychologist specialising in brain injury, estimates that 750 people in Dorset could have full-blown foetal alcohol syndrome, with another 6,500 less severely affected.

The incurable disorder - the biggest preventable cause of learning disability - is caused solely by the mother drinking during pregnancy.

Children of heavy drinkers are most likely to have the syndrome, sometimes diagnosed by characteristic facial features, slow growth and abnormalities such as a small head or lack of co-ordination.

Between one and three in every 1,000 babies are affected.

But there is growing evidence that even low doses of alcohol or binge drinking in pregnancy can lead to children developing behavioural problems.

One in 100 babies has some form of foetal alcohol spectrum disorder.

Experts believe the condition is often not spotted and wrongly labelled as attention deficit hyperactivity disorder or conduct disorder in childhood, sometimes leading to a diagnosis of personality disorder in adults.

If diagnosed early and correctly, making sure children and their families receive the right support can give a more hopeful outcome.

Dr Moffat, who works at Dorset HealthCare Trust's Brain Injury Unit at Poole Community Health Clinic, said: "A lot of people don't know they've got it.

"A lot of people don't know expectant mums who drink could put their foetus at risk.

"Even if pregnant women drink heavily, only 40 per cent of their babies will develop the full disorder, but it's not good odds.

"Sixty to 70 per cent of expectant mothers drink alcohol.

"The difficulty is saying whether there's a safe limit.

There doesn't appear to be."

He explained that alcohol freely crosses the placenta, giving near-equal concentrations of alcohol in both mother and unborn baby.

The effect is to kill off foetal cells and reduce the rate at which they multiply.

Blood flow and oxygen to the baby's brain and body are also affected.

Dr Moffat said the first three to six weeks of brain development were the critical time for heavy drinkers, but there was also a link between binge drinking in early pregnancy and learning difficulties and antisocial behaviour in adolescence.

He pointed out that more young women were binge drinking, and could be doing so before they even realise they are pregnant.

Five years ago, 3.6 million British women were drinking more than the recommended limit of 14 units a week, an increase of 70 per cent in 14 years.

The guideline was changed to no more than three units a day to discourage binge drinking, but 14 per cent of women still regularly drink more than 21 units a week and eight per cent have 42 units a week.