Data Impact blog

Roisin Ryan explores data from the Millennium Cohort Study to understand if there is evidence of a link between drinking during pregnancy and autism in their child.

At present, women in the UK are advised to abstain from alcohol in pregnancy completely, but studies have estimated that up to 75% of women in the UK drink some alcohol during pregnancy.

Drinking alcohol in pregnancy has been shown to affect the brain development of children – with fetal alcohol syndrome disorder being the most well-known disorder. Some recent studies have also suggested a link between alcohol in pregnancy and autism spectrum disorder.

Autism spectrum disorder (ASD) is a neurodevelopmental disorder that affects 1 in 130 people worldwide.

It is a ‘spectrum’ disorder because the symptoms of autism can vary a lot from person to person. People with ASD may have difficulty communicating and forming relationships with others, and view the world differently to those without autism. They may also have difficulty with abstract concepts and with language development.  Overall, it results in a large burden for individuals, their families, and the state, and is estimated to cost 25 billion annually in the UK.

Our study used the Millennium Cohort Study data to investigate if alcohol use in pregnancy was associated with a childhood diagnosis of autism spectrum disorder.

The Millennium Cohort Study (MCS) is an ongoing study of 18,827 children born in the United Kingdom (UK) between 2000 and 2002, which makes it a valuable source of data that can be used to investigate many research questions.

This cohort study has conducted six interviews of parents and their children so far – at age nine months, three, five, seven, 11  and 14 years, and gathered information on parenting, childcare and schooling, behaviour and development, child and parental health, parent’s employment and education, income, housing, neighbourhood, social capital and ethnicity. This detailed information means that this is a good source of data to look at the association between alcohol drinking in pregnancy and ASD because we can take account of other known risk factors for ASD in our analysis.

Two thirds of the women interviewed in this study stated that they did not drink any alcohol during pregnancy. One in four reported light drinking, one in twenty reported moderate drinking and one in fifty reported heavy drinking.

There were patterns in the types of women who drank:

• Light drinkers were older, better educated, married, had a better income and were less likely to be overweight.
• Heavy drinkers tended to be the youngest, unmarried, smoke during pregnancy and come from low income households.

We made sure to take account of these findings in our analysis, so that we could be sure that any association we found between drinking in pregnancy and autism spectrum disorder wasn’t actually due to smoking, for example.

The results of this study found no connection between light and moderate alcohol consumption during pregnancy and children’s subsequent diagnosis of autism spectrum disorder.

Because of the limited number of cases, it was hard to draw a conclusion regarding the association between heavy alcohol consumption during pregnancy and children’s subsequent diagnosis of autism spectrum disorder.

This is important as it is important to provide up to date advice on alcohol drinking to women who are pregnant, or considering becoming pregnant. This finding adds to other studies which have been done which also suggest that low to moderate alcohol consumption in pregnancy does not increase the risk of autism spectrum disorder.

Data from the Millennium Cohort Study is available from the UK Data Service.

Dr Roisin Ryan is an obstetrics and gynaecology trainee in the Irish National Maternity Hospital Hub. She graduated with first class honours from medicine at University College Cork in 2015, and is currently completing an MSc Epidemiology through the London School of Hygiene and Tropical Medicine.