Monday January 27 2014
Heavy drinking in pregnancy can seriously affect a baby's health
“One binge in pregnancy ‘harms child years later’: Children ‘more likely to be badly behaved’ if their mother drinks more than two glasses of wine,” reports the Mail Online.
Obviously, binge drinking in pregnancy is never going to be good for the baby. Though the study the Mail reports on only found slightly increased levels of hyperactivity and behaviour problems in children at seven years old born to mothers who binge-drank during pregnancy.
However, this effect was not strong enough to result in an increase in risk of a child having clinically significant (above cut-off “scores” using a diagnostic checklist) hyperactivity, behaviour problems, emotional symptoms, or peer problems.
It should also be noted that a unit of alcohol in this Danish study (12g) is 4g more than a UK unit of alcohol (8g). ‘Binge drinking’ in this study equated to drinking 7.5 UK units on a single occasion; which would be around three and a half standard glasses of wine.
The UK Chief Medical Officer's advice to women is:
“Women who are pregnant or trying to conceive should avoid alcohol altogether. However, if they do choose to drink, to minimise the risk to the baby, we recommend they should not drink more than one to two units once or twice a week and should not get drunk.”
This study supports this guidance, but the results of this study should not panic women who may have binged inadvertently, possibly before they realised they were pregnant.
Where did the story come from?
The study was carried out by researchers from the University of Copenhagen and the Department of Public Health, Copenhagen. It was funded by the Department of Psychology, University of Copenhagen; Ludvig og Sara Elsass Foundation; Aase og Ejnar Danielsens Foundation; Carl J. Becker’s Foundation; the Lundbeck Foundation; Børne- og Ungdomspsykiatrisk Selskab i Danmark; Dagmar Marshalls Foundation; The A.P. Møller Foundation for the Advancement of Medical Science; and Direktør Jakob Madsens Legat.
The study was published in the peer-reviewed journal European Child & Adolescent Psychiatry.
The Mail Online’s headline was attention grabbing, but inaccurate. The study did not prove that it was binge drinking that affected the child.
In fact, there were a number of significant differences in the women who binge drank in late pregnancy and women who didn’t drink, such as income and history of psychological disorders; all of which could have had an influence on the development of the child.
Although it is advisable to try and heed the advice of the UK Chief Medical Officer to avoid or limit alcohol intake, the current study found that binge drinking was only associated with subtle differences in a parent’s assessment of their child’s hyperactivity and behaviour problems.
It should be noted that the two glasses of wine in the Mail Online headline refers to two large glasses of wine (250ml), equivalent to two-thirds of a bottle.
What kind of research was this?
This was a cohort study using information from the Danish National Birth Cohort. It aimed to investigate the association between maternal binge drinking in early and late pregnancy with child behaviour and emotional development at age seven. The researchers thought that maternal binge drinking in late pregnancy could be associated with worse behaviour and emotional development.
Cohort studies cannot show causation, as there are other factors (confounders) that could be responsible for any association seen. And when dealing with an issue as complex as childhood emotional development, the number of potential confounders is going to be high.
However, given the evidence that alcohol intake in pregnancy harms the baby, it is likely that a cohort study will provide the best evidence on this topic. The gold standard for medical evidence, a randomised control trial, would (we would hope) never be performed due to ethical reasons.
What did the research involve?
The researchers wanted to determine whether maternal binge drinking in early and late pregnancy was associated with differences in child behaviour and emotional development.
The study included 37,315 women with complete information on binge drinking during pregnancy who went on to have a single baby born at term (at 37 weeks gestation or more).
During pregnancy, at approximately 16 and 30 weeks gestation, women were asked questions regarding their drinking in telephone interviews, and again six months after giving birth.
Binge drinking was defined as an intake of five or more alcohol containing units on a single occasion (one unit was equivalent to 12g of pure alcohol – the UK uses a different system where one unit is equivalent to 8g of pure alcohol).
Based on their answers, women were divided into three groups:
- a ‘no binge’ group: women who did not report binge drinking in any interview
- ‘early bingers’: women who reported binge drinking in early pregnancy only (before 16 weeks gestation)
- ‘late bingers’: women who reported binge drinking in late pregnancy only (between 30 weeks gestation and birth)
Women who reported binge drinking in the middle of pregnancy or both early and late pregnancy were excluded.
When the children were seven years old, behaviour and emotional development were assessed using the Strengths and Difficulties Questionnaire. This is a well validated questionnaire used to assess hyperactivity, conduct (behaviour), emotional symptoms and peer problems, as perceived by the parents.
The researchers compared scores on the Strengths and Difficulties Questionnaire from children whose mothers binge drank during early and late pregnancy with those from children whose mothers did not binge drink. They adjusted for a number of confounders that could explain any association seen, such as maternal education, psychiatric diagnoses, age and smoking status.
What were the basic results?
Children exposed to binge drinking in early or late pregnancy had higher ‘externalising’ scores at age seven than children not exposed to binge drinking.
‘Externalising’ is a psychological term meaning that a child has certain behavioural traits that they exhibit to the outside world, such as aggression or delinquency (as opposed to internalising traits, such as lack of self-esteem or a tendency towards depression).
‘Externalising’ scores were obtained by combining the scores on questions that assessed hyperactivity and conduct (behaviour). The effect was bigger in children exposed to binge drinking in late pregnancy.
The ‘relative change in mean (average)’ was 1.02 (95% confidence interval (CI) 1.00 to 1.05) for early bingers compared to no bingers and 1.21 (1.04 to 1.42) for late bingers compared to no bingers.
The researchers also set cut-offs for hyperactivity, emotional symptoms, peer problems and conduct problems. There was no statistically significant association between binge drinking during any period and scores above the cut-offs.
How did the researchers interpret the results?
“Exposure to binge drinking in early and late pregnancy is associated with elevated externalising scores, particularly so in late pregnancy. No increased risk for any of the above cut-off scale scores was observed.”
They went on to say that this showed that “being exposed to just one or two binge drinking episodes in early or late pregnancy was associated with an increased risk of subtle behaviour differences at age seven. However, the estimates were much higher for the late bingers compared to the early bingers.”
This study found that children of mothers who binge-drank during pregnancy had slightly increased levels of hyperactivity and behaviour problems at age seven, according to their parents. However, this effect was not strong enough to result in an increase in risk of hyperactivity or behaviour problems (defined as having a score above a cut-off), or in problems with emotion or with peers.
There are several limitations of this study, most of which were acknowledged by the researchers:
- This is a cohort study and therefore it cannot show that binge drinking caused the slight increase in hyperactivity and behaviour problems.
- The mothers who binge-drank during late pregnancy were different to other mothers: they were less well educated, more likely to smoke, and more likely to have at least one psychiatric diagnosis. This suggests other factors could be responsible for the association seen that were not adjusted for.
- Parents reported on the child’s behaviour and emotional development, which could lead to inaccurate or biased reporting.
In light of the evidence provided in the study it would appear unlikely that a few too many glasses of wine during pregnancy – while certainly not recommended – will permanently influence how a child will develop emotionally in later life.
Childhood emotional development is an extremely complex issue and many parents whose children do develop behavioural and emotional problems will find that they do so for no apparent reason.
Often, these types of problems are not somebody’s ‘fault’, they just occur.
Analysis by Bazian. Edited by NHS Choices.
Follow Behind the Headlines on Twitter.
Join the Healthy Evidence forum.