LONDON - Women who drink even moderate amounts of alcohol while
pregnant may risk lowering child's intelligence levels, according to a
study by British scientists.
Advice to pregnant
women about drinking is contradictory, with some guidelines recommending
no alcohol at all and others suggesting the odd drink now and then is
safe.
But in a study described as "hugely
important" by one expert, researchers using genetic analysis of more
than 4,000 mothers and children found that drinking between one and six
units of alcohol a week during pregnancy can lead to lower Intelligence
Quotient (IQ) scores by the time a child is eight.
"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 fetus to clear this alcohol," said Sarah
Lewis of Bristol University, who led the study. "This is evidence that
even at these moderate levels, alcohol is influencing fetal brain
development."
This study used genetic data from women and children who were part of another study called the Children of the 90s study.
Since the individual genetic variations that people have in their DNA
are not connected to lifestyle and social factors, this kind of study
avoids potential complications.
Most previous
studies have used observational evidence, but experts say this can be
misleading because, for example, mothers who drink in moderation while
pregnant are typically also well educated, have good diets and are
unlikely to smoke—all factors linked to higher IQ in children and which
could mask any negative effects of alcohol.
A US study published in July found that older, educated women are more likely to drink while pregnant.
Genes affect alcohol metabolism
This study, published in the journal PLOS ONE on Wednesday, used a new
technique analyzing the genetic variants which modify the effects of
alcohol exposure levels.
When a person drinks alcohol, ethanol is converted to acetaldehyde by a group of enzymes, the researchers explained.
Variations in genes that 'encode' these enzymes lead to differences in a
person's ability to metabolize ethanol, so in "slow metabolizers",
alcohol levels may be higher for longer than in "fast metabolizers".
Scientists think fast ethanol metabolism protects against abnormal brain
development because less alcohol goes to the fetus.
The mothers were asked to record their alcohol consumption at various
stages during pregnancy, and one drink was specified as one unit of
alcohol.
The results showed that four genetic
variants in alcohol-metabolizing genes among the 4,167 children were
strongly related to lower IQ at age eight. The child's IQ was on average
almost two points lower per genetic variation they had.
The effect was only seen among children of women who were moderate
drinkers and there was no effect evident in children of mothers who
abstained during pregnancy. This strongly suggests it was exposure to
alcohol in the womb that led to the difference in child IQ, the
researchers said.
"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." said Ron Gray of
Oxford University, who was part of Lewis's team.
David Nutt, a professor of neuropsychopharmacology at Imperial College
London who was not involved in the research, said it was "a hugely
important study from the best UK cohort that can study this question".
"Even though the IQ effects are small, if at all possible women should
avoid ethanol in pregnancy as it's a known toxin," he said in an emailed
comment. –Reuters
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