Teenagers are significantly more likely to be unruly, aggressive and badly behaved if their mothers drank early in pregnancy, a study has found.
As little as one alcoholic drink a day during the first three months of pregnancy was enough to increase the risk of "conduct disorder" in 16-year-olds three-fold, said researchers.
Conduct disorder is defined as a pattern of behavioural problems that includes aggression, destruction of property, deceitfulness or theft, and serious rule-breaking.
For the study, US scientists led by Dr Cynthia Larkby, from the University of Pittsburgh, monitored 592 children from birth to age 16.
Information was collected about the drinking habits of the children's mothers, including quantity, frequency and the pattern of alcohol use.
The researchers found that teenagers exposed to an average of one or more alcoholic drinks a day in the womb were three times more likely to be diagnosed with conduct disorder than those whose mothers drank less or abstained.
However, the association was only significant when alcohol was consumed during the first three months of pregnancy.
The scientists wrote in the Journal Of The American Academy Of Child And Adolescent Psychiatry: "From a clinical perspective, prenatal alcohol exposure should be considered as another risk for conduct disorder. The next steps in research should be to define the interactions between prenatal exposures, environmental factors, and heritability."
It is known that heavy drinking during pregnancy can result in foetal alcohol syndrome, which may lead to stunted growth, heart defects, and impaired brain development.