Teenagers whose mothers drank early in pregnancy are more likely to become unruly, aggressive and badly behaved, researchers claim. According to their study, the risk of anti-social behaviour rose threefold among 16-year-olds whose mothers drank as little as one alcoholic drink a day during the first three months of pregnancy, reports the Daily Mail . The U.S. study of almost 600 youngsters analysed rates of 'conduct disorder' at regular intervals from their birth.

Conduct disorder was defined as a pattern of behavioural problems that included aggression towards people and animals, destruction of property, deceitfulness, theft and serious rule-breaking.

The risk of 'lifetime' bad behaviour patterns went up threefold with one or more drinks a day compared with drinking less, or abstaining. There was no extra risk linked to drinking at a later stage in the pregnancy.

Dr Cynthia Larkby, from the University of Pittsburgh, monitored 592 children from birth to age 16, half of whom were African-American with the other half white.

Information was collected about the drinking habits of the children's mothers, including quantity, frequency and the pattern of alcohol use. "From a clinical perspective, prenatal alcohol exposure should be considered as another risk for conduct disorder," the researchers said.