Moderate Drinking During Pregnancy is Not Safe, Affects Child's IQ

Consumption of alcohol during pregnancy has always been a topic of debate. There were studies supporting moderate drinking as safe while some studies suggest a complete abstinence.

According to the new study by the researchers at the University of Bristol and Oxford, pregnant women may have to completely stay from the alcohol. Even small levels of exposure to alcohol while in the womb can influence a child's IQ, said the new study. This conclusion is based on data that included 4,000 mothers and their children of the 90s study.

Prior to this, there were studies with conflicting and inconsistent evidence on the effects of moderate alcohol intake on a child's IQ. The reason for this could be the difficulty to separate the effects of moderate alcohol consumption from other lifestyle and social factors, such as smoking, diet, affluence, mother's age and education.

This is the first study to use genetic variation in order to investigate the effect of moderate drinking during pregnancy. Moderate level of alcohol was between one units and six units of alcohol per week.

This method involves no complication as the DNA is not influenced by the lifestyle and social factors.

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 modification they possessed.

But this was noticed among children whose mothers were used to moderate drinking. 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.

The study however did not focus on heavy drinkers.

According to the report, the ethanol in the alcoholic drinks is converted to acetaldehyde by a group of enzymes. Variations in the genes that 'encode' these enzymes lead to differences in their ability to metabolize ethanol. In 'slow metabolisers', peak alcohol levels may be higher and persist for longer than in 'fast metabolisers'.

'Fast' metabolism of ethanol protects against abnormal brain development in infants because less alcohol is delivered to the fetus. Yet the exact mechanisms are still unclear.

Previous studies have relied on observational evidence, where moderate drinking was beneficial because mothers drinking moderately during pregnancy were typically well educated, having a good diet and unlikely to smoke. These are the factors which are linked to higher IQ in the child, and which erase negative effect that exposure to alcohol may have.

But what is unique about this study is that it focuses on moderate alcohol intake in over 4,000 women and used a novel technique known as Mendelian randomization, to investigate the links between exposures and later diseases, using genetic variants which modify exposure levels and which are not influenced by lifestyle or other factors.

The mothers' alcohol intake was based on the questionnaire completed when they were 18 weeks pregnant. The questionnaire included questions on the average amount and frequency of alcohol consumption before the current pregnancy, during the first trimester, and in the previous two weeks or at the time when they first felt the baby move. One drink was specified as one unit of alcohol.

Another questionnaire was answered by mothers at around 32 weeks of gestation. It asked about her average weekday and weekend alcohol consumption, from which weekly intake was derived.

It was observed that any woman who reported drinking, even if it was less than one unit per week either in the first trimester or when she felt the baby first move was classified as drinking during pregnancy.

At approximately 18 and 32 weeks of pregnancy, the women were also asked on how many days during the past month they had drunk two pints of beer. Any women who reported doing this on at least one occasion was classified as a binge drinker for the purposes of this analysis and were excluded.

Using a shortened version of the Wechsler Intelligence Scale for Children, they tested the children's IQ.

Speaking about the findings, the report's main author, Dr Sarah Lewis, 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 fetus to clear this alcohol. This is evidence that even at these moderate levels, alcohol is influencing fetal 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 good reason to choose to avoid alcohol when pregnant.'

The study was published on November 14 in PLOS ONE.