Ellen Phiddian
Cosmos science journalist
When you’re pregnant, most guidelines recommend keeping caffeine intake to roughly 200mg (or 1 espresso) per day.
But the evidence on coffee and pregnancy is still contested. A new study hasn’t found any strong links between coffee drinking during pregnancy and child brain development.
The study, done on a Norwegian cohort, is published in Psychological Medicine.
The researchers say that pregnant people should still follow medical guidelines on caffeine, but if their results are supported by other evidence, those guidelines may eventually be adjusted.
Previous studies have often suggested that drinking coffee or other caffeinated drinks during pregnancy can affect the brain development of children.
Part of the reason is thought to be that caffeine doesn’t break down as easily in the body of pregnant people, and can accumulate.
But many of these studies, according to the Australian, UK and Norwegian researchers, are affected by other factors. For instance, women who drink coffee while pregnant are more likely to smoke and drink alcohol as well, both of which are known to cause harm.
The research team drew on data from the Norwegian Mother, Father, and Child Cohort Study, which recruited more than 95,000 pregnant women in the period 1998-2008.
The longitudinal study has recorded the health, lifestyle, and genetic data of these mothers, as well as the data of their children and the fathers of their children, checking in roughly annually.
“Ideally, in medical research, we would do randomised-control trials to look at whether there’s a cause and effect,” study co-author Dr Gunn-Helen Moen, a researcher at the University of Queensland, tells Cosmos.
“But for many reasons, we can’t do that in pregnancy – it’s ethically problematic to randomise individuals to do things that may or may not be harmful for their children.”
Running a trial over a 10-year time period or longer, like this study, is also an extremely costly venture, adds Moen.
Instead, the team looked at genetic variations linked to coffee-drinking behaviour in the cohort, alongside survey data on parental coffee consumption during pregnancy, and neurodevelopmental difficulties in the children. Fathers’ coffee drinking was used as a control against mothers’ coffee drinking.
“There’s a method called Mendelian randomisation, which takes advantage of the fact that whether we get a certain genetic variant or not from our parents is a random process,” says Moen.
“We can use statistical methods to mimic a randomised-control trial, essentially.
“So when we look at these genetic variants for how much coffee an individual is likely to drink, that exposure is not associated with all of these other conflicting variables, and we can draw conclusions on that basis.”
Overall, the researchers could find no link between coffee drinking during pregnancy and child brain development.
“For all of our analysis, it does look like it’s smoking and alcohol that is probably the driver of this observational relationship,” says Moen.
But there could also be genetic factors at play, she adds. For instance, it’s possible people with a genetic predisposition to ADHD are also more likely to drink alcohol during pregnancy.
Moen says the study should be generalisable to people in other countries.
“Norwegians are maybe a little bit special in the fact that they drink a lot of coffee – more than the average,” she says.
“But we’ve done a similar study looking at birth weight and the risk of miscarriage and stillbirth in the UK Biobank – a British population – and found similar evidence.”
Currently, the researchers aren’t proposing any change to guidelines on caffeine in pregnancy. But Moen says that the team’s research is starting to show that alcohol and smoking may be the primary culprits making caffeine look dangerous.
“Long-term, once we get more of these studies out there, there might be reason to consider updating the advice,” says Moen.
