Consuming alcohol during pregnancy can damage the fetal central nervous system, which in turn can disrupt the learning abilities of the fetus, researchers from the Queen's University of Belfast have found.

"When examined after birth, individuals who have been prenatally exposed to alcohol exhibit a wide range of behaviours that are indicative of central nervous system dysfunction. These can include poorer abilities to learn, deficits in attention, poorer abilities to plan and organise, and an inability to learn about the consequences of actions. As a consequence, they may demonstrate behavioural difficulties and social problems which might lead to problems at school, and often trouble with the law," said Peter G Hepper, professor of psychology at Queen's University.

A study conducted on more than 75 mothers has found that drinking during pregnancy can have a major impact on the fetal habituation or learning abilities while still residing in the mother's womb.

During the study, researchers examined 78 non-smoking mothers with normal, apparently healthy, single pregnancies from the Royal Jubilee Maternity Service in Belfast. Details of the mothers' alcohol consumption were obtained through questionnaires completed at 12 to 14 and 18 to 20 weeks gestation as well as semi-structured interviews at 34 weeks of gestation.

Following identification of the mothers' drinking habits, five groups of fetuses were examined: mothers who did not consume alcohol, mothers who consumed moderate amounts of alcohol during the week, moderate amounts consumed during a binge period, heavy amounts consumed during the week, and heavy amounts consumed during a binge period. Fetal performance was examined on three occasions, seven days apart, beginning at 35 weeks of gestation.

Then researchers used a process of habituation, which is the ability of an organism to stop responding to repeated stimulation. This reflects the ability of the central nervous system to learn to recognise a particular stimulus. It is widely accepted that habituation represents a basic form of learning.

The study found that fetuses of mothers who binge drink five to 10 drinks per week, or have more than 20 drinks a week drunk evenly, or as a binge over two to three days, take significantly longer to habituate.

The study also showed that binge drinking was associated with more variability of the fetus to learn. For normal learning and development, the fetal brain requires stability and this result implies that binge drinking impaired this function.

"One 'oddity' of prenatal exposure to alcohol is there are large individual differences in its effects. Some individuals whose mothers drink heavily may exhibit few effects whilst others whose mothers drink less may exhibit much greater effects. By observing the behaviour of the fetus it will be possible to ascertain which and by how much individuals have been affected by exposure to alcohol. To be safe, however, no drinking during pregnancy would be wise," said Hepper.