Women are being warned to watch what they eat during pregnancy because it might have "long term consequences" for their babies.

A decade of research indicates that taste preferences are set early in life, and even in the womb.

The evidence points to mothers not only influencing the future eating habits of their children, but also problem behaviour such as addiction.

Several studies were described by French expert Dr Benoist Schaal at the annual meeting of the American Association for the Advancement of Science (AAAS) in Vancouver, Canada.

Dr Schaal, from the CNRS research institute in Dijon, conducted one study in which 12 pregnant women were given cookies and sweets laced with aniseed.

Responses of their babies were measured up to four days after birth and compared with those of a similar number of unexposed infants.

Those babies which had previously "tasted" the strong flavour in the womb seemed attracted to it. They smiled and moved towards the aniseed smell.

Non-exposed babies turned away and looked disgusted.

Babies in the womb could sense flavours by inhaling amniotic fluid, said Dr Schaal.

"During pregnancy a woman is relatively vulnerable to her environment," he said. "What the mother takes in a certain dose goes also to the foetus during a period when the brain is being formed, probably with long-term consequences."

Another study linked fussy eating with the variety of foods presented to weaning children.

One group was fed nothing but carrots for 10 days. Another was given three different kinds of food, and a third had still more variety.

Later all the children were offered "new" foods in the form of pureed ham or fish. Those children who had previously been offered a wider range of foods accepted them more easily.

Research had also found an association between tobacco use in children and smoking exposure during pregnancy.

A study of 1,000 children showed that exposure to smoking in the womb was the strongest predictor of pre-adolescents picking up the habit by age 12, said Dr Schaal.

"If we want to have an action on different kinds of maladaptive behaviours or addictions I would say one target for health policies would be in gestating and lactating women," he said.