Relatively small levels of exposure to alcohol while in the womb can influence a child’s IQ, according to researchers from the universities of Bristol and Oxford.
Current advice to pregnant women about moderate alcohol consumption is contradictory with some guidelines recommending complete abstinence and others suggesting moderate use is safe.
The new study, published last week in the online journal PLOS ONE, used genetic variation to investigate the effects of 1-6 units or more of alcohol per week during pregnancy among 4,167 women and their children. Heavy drinkers were not included in the study.
They found four genetic variants in alcohol-metabolising genes among the children were strongly related to lower IQ at age eight. IQ was on average almost two points lower per genetic modification they possessed.
But the effect was only seen among the children of women who were moderate drinkers. There was no effect evident among children whose mothers abstained from alcohol during pregnancy.
Lead author Dr Sarah Lewis said: “Our results suggest that even at levels of alcohol consumption 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.”
Janet Fyle, professional policy advisor at the Royal College of Midwives, said: “This adds weight to the RCM’s advice that women should avoid alcohol when they are pregnant or planning a pregnancy… and that cumulative alcohol consumption has damaging effects on the foetus.”
Dietician Catherine Collins, from St George’s Hospital NHS Trust in London, said alcohol was likely to stay longer in the bodies of unborn babies with the susceptibility genes and do more damage.
She added: “What do mums take from this? Unfortunately it’s a bit of a gene lottery.
“If your child has a particular gene profile, drinking any alcohol in pregnancy will have an effect on IQ - but, and it’s a big but - your child may not have one of those identified gene defects, and so the effect is negligible.”