Lead researcher Dr Ron Gray from the National Perinatal Epidemiology Unit at the University of Oxford 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. So women have good reason to choose to avoid alcohol when pregnant.’
Current advice to pregnant women about alcohol during pregnancy is contradictory: some official guidelines recommend complete abstinence while others suggest that moderate alcohol consumption is safe.
Previous studies on the effects of moderate alcohol intake on a child’s IQ have produced conflicting results. This may be because it is difficult to separate the effects of moderate drinking from other lifestyle and social factors, such as smoking, diet, affluence, and mother’s age and education.
This study, believed to be the first substantial one of its kind, used a different approach to look at moderate alcohol intake during pregnancy and the children’s IQ. It used genetic variation to investigate the effects of drinking 1–6 units of alcohol per week among a large group of over 4,000 women.
A small, 125ml glass of wine is around 1.5 units while a pint of beer of standard strength is approximately 2 units. Heavy drinkers were not included in the study.
Since the individual variations that people have in their DNA are not connected to lifestyle and social factors – they are randomly assorted across the population – this genetic approach removes the potential complication of these other factors influencing the result.
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.
Dr Ron Gray
The researchers found four genetic variants in alcohol-metabolising genes among the children that were strongly related to a lower IQ at age eight. The child’s IQ was on average almost two points lower per genetic modification they possessed. Crucially, 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.
The research used data from over 4,000 mothers and their children in the Children of the 90s study (also known as ALSPAC), and is published in the journal PLOS ONE.
The mothers’ alcohol intake was based on questionnaires completed when they were 18 weeks and 32 weeks pregnant.
The children’s IQ was tested when they were aged eight using a shortened version of the Wechsler Intelligence Scale for Children.
Variations in genes that encode alcohol-metabolising enzymes can lead to differences in how long alcohol persists at high levels in the body, which it is thought could affect the development of the fetus.
‘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,’ said Dr Sarah Lewis from the University of Bristol, the report’s first author. ‘This is evidence that even at these moderate levels, alcohol is influencing foetal brain development.’
Dr Simon Newell, Vice President for Training and Assessment at the Royal College of Paediatrics and Child Health commented: ‘This research serves to confirm that drinking even a small amount of alcohol whilst pregnant can do harm to your unborn child. We already know that an estimated 6,000 babies a year in the UK are born with brain damage, physical problems or learning disabilities as a result of heavy alcohol consumption by their mother whilst pregnant.
‘It is 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.’
The Children of the 90s study, also known as the Avon Longitudinal Study of Parents and Children (ALSPAC), is a long-term health-research project based at the University of Bristol. It enrolled more than 14,000 pregnant women in 1991 and 1992 and has been following the health and development of the parents and their children in detail ever since. It is funded by the University of Bristol, the Wellcome Trust and the Medical Research Council.