PREGNANT women who smoke may harm their babies' brain development if they turn to e-cigarettes to satisfy their nicotine craving, scientists have warned. 

New research suggests that e-cigarette vapour may be as damaging as tobacco smoke to the nervous systems of the foetus or newborn infant. 

The early findings, based on studies of mice, show that exposure to volatile chemicals from the devices disrupts the activity of thousands of genes in the developing frontal cortex, the brain region responsible for higher mental functions. 

Analysis of the altered gene activity patterns indicated that they could lead to reductions in learning, memory and co-ordination, and increases in hyperactive behaviour. 

These are just the sort of neurological effects seen in children whose mothers smoked during pregnancy and who are known to be at risk of attention deficit hyperactivity disorder (ADHD) and learning difficulties. 

A further study, still on-going, has shown that older mice exposed to e-cigarettes in the womb or just after birth do indeed appear to be hyperactive, running around at a faster rate than normal. 

Lead scientist Professor Judith Zelikoff, from New York University in the US, said: "This is ground-breaking research. 

What it shows is that there is certainly some concern over the safety of e-cigarettes, particularly in relation to pregnant women or young infants. 

"There are potential dangers revealed by these studies indicating a possible impact to the unborn child that may be seen at birth but may occur later in the life of the child. 

"Women may be turning to these products as an alternative because they think they're safe. Well, they're not." Colleague Dana Lauterstein, a PhD student at the university who did much of the work, added: "Most people view e-cigarettes as a safe way to smoke. For women who are pregnant, this could be dangerous. 

They could unwittingly be endangering their child." Prof Zelikoff's team started out expecting to see effects from nicotine, which previous research has suggested may have an impact on brain development. 

The whole point of e-cigarettes is that they deliver a dose of nicotine minus the highly damaging cocktail of other chemicals found in tobacco. 

For this reason they have been touted as a "healthier" alternative for smokers who lack the will to quit, or a cessation aid that can help to wean them off tobacco. 

But recent studies have challenged the view that apart from its addictive properties, nicotine on its own is harmless. 

And the new research shows that other e-cigarette chemicals besides nicotine have an even bigger effect on developing nervous systems than the tobacco compound.