Children who have certain variants in alcohol metabolizing genes and whose mothers drank while pregnant may have a lower IQ than those whose mothers did not drink during pregnancy, researchers report.
Sarah Lewis (University of Bristol, UK) and colleagues point out that despite their findings, causation between maternal alcohol consumption and childhood IQ cannot be proven due to the nature of their study design.
Independent expert David Leon (London School of Hygiene and Tropical Medicine, UK) commented in a press statement: "This study is the first of its kind. As the authors make clear the statistical association they find is not the same as showing that drinking in pregnancy actually causes a reduction in childhood IQ. Further studies are needed before clear and firm conclusions can be reached."
Lewis and team found that four genetic variants in the alcohol metabolizing genes ADH1A (rs2866151), ADH1A (rs975833), ADH1B (rs147536), and ADH7 (rs284779) in 4167 children were strongly related to them having a lower IQ (assessed using the Wechsler Intelligence Scale) at the age of 8, as was a risk allele score based on these four variants.
This effect was only seen among the children of mothers who drank moderately (1‑6 units of alcohol per week during pregnancy), at a per-allele effect estimate of ‑1.80, with no significant effect on children whose mothers abstained during pregnancy.
As reported in PLoS One, another genetic variant, ADH4 (rs4148884) in mothers was associated with their child's IQ, but again only among mothers who drank moderately during pregnancy.
"What do mums take from this? Unfortunately it is 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 five identified gene defects, and so the effect is negligible," remarked another independent expert, Catherine Collins (St George's Hospital, Tooting, UK).
Simon Newell, Vice President at the Royal College of Pediatrics and Child Health, London, UK, added: "It's impossible to say what constitutes as a 'safe' amount of alcohol a mother can drink as every pregnancy is different, so our advice to mothers is don't take a chance with your baby's health ‑ drink no alcohol at all."
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