A US study found that children who were exposed to cocaine while still in the womb were likely to have an IQ three points lower than peers who had not been exposed.

It estimated that each year more than 80,000 American children will fail in school and need special education services because they were exposed to cocaine in the womb.

The research put the cost of helping these children at up to $352m (�220m) a year.

Drug effects

Cocaine is a drug that stimulates the central nervous system.

It acts on the areas of the brain that produce feelings of pleasure and produces heightened pleasure and increased confidence.

Other immediate effects include dilated pupils and elevated blood pressure, heart rate, respiratory rate and body temperature.

The health risks are well-documented. While occasional use can cause a stuffy or runny nose, it can also trigger heart attacks. Long-term use can destroy the lining of the nose.

Injecting cocaine with contaminated equipment can cause AIDS, hepatitis, and other diseases.

Research findings

Researchers from Brown University School of Medicine, Providence, Rhode Island, used information gathered in eight other research studies.

Altogether, these involved 800 school-age children.

Children took IQ tests

The researchers looked at their performance in IQ tests, where verbal and reasoning skills are tested to determine an individual's intelligence quotient.

On average, children who had been exposed to cocaine had IQ scores 3.26 points lower than the average of children who were not exposed to the drug.

The effect was twice as pronounced in language tests measuring speaking ability and comprehension.

The researchers said that a three point IQ reduction was not too serious in itself.

But it was likely to have more impact in these cases because children from backgrounds where drug taking was common were likely to have lower IQs anyway.

Figures for the number of children born to cocaine users each year were based on statistics from the US National Pregnancy and Health Study and the US General Accounting Office.

Changing picture

Professor Barry Lester led the study, which is published in the journal Science.

He said the picture was an improvement on the popular image of children hopelessly brain-damaged by cocaine that emerged a few years ago.

But he warned there was no room for complacency.

"We started out with hysteria about cocaine devastation, and it would be dangerous for the pendulum to swing to the other side and say the effects aren't there or they are all environmental," he said.

Level of use

The number of regular cocaine users in the US has declined by 75% since 1986.

A 1995 survey estimated that 1.45 million Americans were current cocaine users - that is, they had used cocaine at least once in the previous month.

In England, one person in 20 has tried the drug, while one in seven has been offered it, according to a Health Education Authority (HEA) survey of 5,000 people.

A spokesman said the new research would influence the authority's drug education campaigns.

"You would think most people would do whatever they could to avoid having a child with lower intelligence than they could have," he said.