HORRIFIC evidence about the damage done to babies when their mothers smoke during pregnancy is revealed today.

It shows that even apparently healthy babies born at normal weight may already be destined for a life of slow learning and disruptive behaviour.

The scientist behind the research claims the effects go far beyond what has been appreciated, including a huge burden of death and brain damage that already eclipses Aids in Third World countries.

Theodore Slotkin, Professor of Pharmacology at Dukes University in North Carolina, says the damage caused to unborn children by nicotine is far worse than that caused by crack cocaine, which receives far more attention in the US.

Slotkin, an award-winning researcher on the effects of tobacco, accuses the medical community, government and media of neglecting unequivocal scientific evidence that nicotine from maternal smoking causes possibly 100,000 foetal deaths each year as well as massive numbers of cot deaths.

Also neglected, he says, are the severe neurological problems in babies of the one in four pregnant women who smoke.

His findings, published in the Journal of Pharmacology and Experimental Therapeutics, are based on a detailed review of research findings, including his own.

Animal studies he has conducted have demonstrated that nicotine inflicts serious damage on the foetus even at levels too low to cause low birth weight, the traditionally accepted sign of damage.

''Maternal smoking during pregnancy kills between tens of thousands and possibly over a hundred thousand babies each year in utero,'' he said yesterday.

''It also results in tens of thousands of admissions to intensive care units after birth and kills or brain-damages more during the birth process. Smoking is also responsible for one-third to two-thirds of all cases of Sudden Infant Death Syndrome (SIDS).

''And none of these figures takes into account the enormous increase in learning disabilities, attention deficit and hyperactivity disorder and other behavioural problems that we know are part of the outcome of maternal smoking.''

Children and adolescents who take up smoking also may suffer brain damage, said Slotkin, who is now exploring this phenomenon in animal studies.

''Most smokers begin smoking in adolescence, and it is quite possible that nicotine exposures in a still-developing adolescent brain also can cause irreversible changes in the development, structure and function of specific nerve pathways,'' he said.

Such effects might explain why nicotine is often more viciously addictive in adolescents than it is in adults, and why the adolescent smoker becomes the lifelong smoker.

Slotkin, whose research is carried out in America's tobacco-farming heartland, said efforts in the US to reduce smoking was putting pressure on the industry to make their profits elsewhere.

''They are doing that very successfully. The World Health Organisation estimates that sometime in the next decade the annual number of deaths from tobacco around the world will pass the 10 million mark, which eclipses virtually any disease we have a chance of controlling.

''Damage from increases in cigarettes smoking certainly eclipses Aids in developing countries, and it will mean a new generation of children exposed to cigarette smoke. The impact on those countries' social structures and economies is unfathomable.

''It's one thing to have a large number of babies needing intensive care in the First World where we have the facilities and can afford it. But in the Third World these babies are just going to die.''

During 10 years of research, the professor and his colleagues used mini-pumps to inject precisely-metered doses of nicotine into the circulation of pregnant rats to study the effect on their offspring, free of any confounding factors.

They found that nicotine mimicked an important brain chemical, acetylcholine, leading to confusion in the way the brain's signalling pathways are formed. It also robbed babies of a survival mechanism provided by the adrenal system, which triggers increases in heart rate and breathing during periods of hypoxia - such as during birth or episodes of sleep apnoea, which can lead to cot death.

He also urged caution over the use of nicotine patches in pregnancy, particularly after the first three months, when the foetus became more vulnerable to the chemical.