Even moderate drinking in pregnancy can lower a child's IQ, new study finds

Children's intelligence can be influenced by even small levels of exposure to alcohol in the womb, according to a new study led by researchers from the universities of Bristol and Oxford.

Current advice to pregnant women about moderate alcohol consumption during pregnancy is contradictory, as it is both recommending complete abstinence and suggesting drinking moderately is safe.

Previous studies have failed to give a categorical answer to the effects of moderate alcohol intake on a child’s IQ, possibly because it is difficult to separate these effects from other lifestyle and social factors, such as smoking, diet, affluence, mother’s age and education.

The study, which looked at moderate alcohol intake in more than 4,000 women, is described as the first substantial one of its kind. It used genetic variation to investigate the effects of moderate (less than 1 to 6 units of alcohol per week) drinking during pregnancy.

As the individual variations that people have in their DNA are not connected to these lifestyle and social factors, this approach ensures these do not affect the results.
The 4,167 children’s IQ was tested when they were aged eight, and four genetic variants in alcohol-metabolising genes among the children were strongly related to lower IQ. The child’s IQ was on average almost two points lower per genetic modification they possessed.  

However, this effect was only seen among the children of women who were moderate drinkers. There was no effect evident among children whose mothers abstained during pregnancy, strongly suggesting that it was the exposure to alcohol in the womb that was leading to the difference in child IQ.

Lead author Dr Sarah Lewis, from the University of Bristol, said, ‘Our results suggest that even at levels of alcohol consumption which are normally considered to be harmless, we can detect differences in childhood IQ, which are dependent on the ability of the foetus to clear this alcohol. This is evidence that even at these moderate levels, alcohol is influencing foetal brain development.’

Dr Ron Gray, from the University of Oxford who led the research, added, ‘This is a complex study but the message is simple: even moderate amounts of alcohol during pregnancy can have an effect on future child intelligence. So women have a good reason to choose to avoid alcohol when pregnant.’

Previous studies, which have relied on observational evidence, found that moderate drinking is beneficial compared to abstention. However, this is because the mothers in these studies who drank in moderation during pregnancy are typically well educated, have a good diet and are unlikely to smoke. These factors are linked to higher child IQ and mask any negative impact of exposure to alcohol.

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