Olivia Henry
Australian Science Media Centre
There is “no safe level” of caffeine consumption for women who are pregnant or trying for a baby, according to an international study released this week. But Aussie experts argue the warnings are “alarmist” and say the study recommendations may unnecessarily worry hopeful and expectant mothers.
The paper reviewed 48 studies over the past 20 years that looked at the effects of caffeine on six negative pregnancy outcomes: miscarriage, stillbirth, childhood leukaemia, low birth weight, childhood obesity and preterm birth.
The author, Professor Jack James from Reykjavik University in Iceland, reported caffeine consumption was associated with miscarriage, low birth weight, stillbirth, low birth rates, childhood acute leukaemia and childhood obesity, but not pre-term birth.
And while he did acknowledge the studies used were observational and cannot prove cause-and-effect, James said the findings seemed to be dose-dependent – that is, that higher caffeine intake seemed to lead to worse pregnancy outcomes.
The advice to completely avoid caffeine is overstated
But Aussie experts have said the advice to completely avoid caffeine is overstated, with the quality of the observational studies a big reason for their scepticism.
Many of the studies in this analysis relied on women to recall their caffeine intake before and during their pregnancy, often a long time after they had given birth or had an “adverse outcome” such as a miscarriage.
“It is well known that people who suffer an adverse outcome are more likely to recall and possibly exaggerate their exposure,” says an obstetrics and gynaecology expert from the University of Melbourne, Dr Alex Polyakov.
“So it is unsurprising that women who suffered one of the adverse pregnancy outcomes examined would be more likely to recall any behaviour that they may consider to be contributory to that outcome, caffeine consumption being one of them.”
Polyakov also says there were far too many variables in each study that could not be easily compared.
“For example, a study conducted in Italy on caffeine consumption would be radically different from a study examining the same research question conducted in China.”
“There are … substantial differences between these two populations, such as ethnicity, metabolism, diet, lifestyle, just to name a few. Therefore to combine such two studies performed on such different populations can only be described by an old acronym borrowed from computer science – GIGO – garbage in, garbage out.”
It might feel like it, but we don’t need caffeine to survive
But while researchers question the strength of the current study, Professor Clare Collins from the University of Newcastle acknowledges there was not much of an alternative.
“The reality is that it is not ethical to conduct randomised trials that administer caffeine in a double-blind manner to see whether caffeine causes harm in human pregnancy,” says Collins, a Professor of Nutrition and Dietetics.
“Together with research from animal studies, which has shown that caffeine can disrupt embryo transport, development, implantation, placental function and increase pregnancy complications, this review should trigger greater caution in regard to caffeine in human pregnancy.”
So what can we take away from this?
Well, Dr Cathy Knight-Agarwal, Clinical Assistant Professor of Nutrition and Dietetics at the University of Canberra, points out that while it may feel like it sometimes, we don’t need caffeine to survive.
“If pregnant women cut out caffeinated products from their diet would this compromise their nutritional status, and the answer is a big no,” she says.
“Therefore, from my perspective the only benefit of consuming such products is perhaps the psychological pleasure they induce – which is all very well and good but is this enough of a reason not to cease consumption during pregnancy?”
The local experts say when it comes down to it, when in doubt, less is best.
“There are so many dos and don’ts associated with pregnancy and the last thing we need is to cause unnecessary anxiety,” says Dr Luke Grzeskowiak, from the University of Adelaide.
“At the end of the day, women should be reassured that caffeine can be consumed in moderation during pregnancy.”
This article was first published on Australia’s Science Channel, the original news platform of The Royal Institution of Australia.
