Contentious study suggests no safe level of caffeine during pregnancy
A new review encompassing dozens of prior observational studies and meta-analyses is suggesting there is no safe level of caffeine consumption during pregnancy. The review suggests a “radical revision” to current health recommendations but not all experts agree with the findings, noting the review is “overly alarmist and inconsistent with the evidence.”
High volumes of caffeine consumed during pregnancy has been long-associated with higher rates of miscarriage, stillbirth and low birth weight. So most health bodies around the world recommend pregnant women limit their caffeine consumption. The general current advice – in the UK, Europe and the United States – is for pregnant women to consume no more than 200 mg of caffeine per day.
As a general rule, a standard cup of coffee contains about 100 mg of caffeine. So current recommendations suggest, for most pregnant women, one to two cups of coffee a day is safe. Although it is worth noting caffeine levels in coffee can vary dramatically depending on how the beverage is prepared, and some popular drinks can contain close to 400 mg of caffeine.
Jack James, from Reykjavik University, has published a new review on the subject, analyzing the quite large body of pre-existing research to investigate whether the evidence backs up current safe caffeine consumption recommendations for pregnant women. From over 1,000 published articles, James focused in on 48 observational studies and meta-analyses published over the past 20 years.
“An extensive body of scientific evidence from original observational studies and meta-analyses provides persuasive confirmation of increased risk from maternal caffeine consumption for at least five major negative pregnancy outcomes: miscarriage, stillbirth, lower birth weight and/or small for gestational age, childhood acute leukaemia and childhood overweight and obesity,” James concluded in his review. “Accordingly, current health recommendations concerning caffeine consumption during pregnancy are in need of radical revision. Specifically, the cumulative scientific evidence supports pregnant women and women contemplating pregnancy being advised to avoid caffeine.”
James’ conclusions are based on examining a large body of observational research, and the usual "correlation is not causation" caveats apply. But, James does infer a potential causal connection, suggesting the consistent dose-response relationships noted across many studies indicate caffeine may indeed be causing negative pregnancy outcomes.
He also points out there have been frequent ethical concerns raised whenever controlled clinical trials on the matter have been discussed. James says there is an ironic ethical paradox in suggesting 200 mg of caffeine is safe for pregnant women, but implying it is possibly unsafe to test that hypothesis in controlled clinical trial conditions.
Nevertheless, a number of experts do not agree with James’ conclusions. Luke Grzeskowiak, from the Robinson Research Institute at the University of Adelaide, says although there is no proven safe level of caffeine consumption for pregnant women, that does not mean all levels of caffeine intake are harmful.
"The author's conclusion that all pregnant women and women contemplating pregnancy should avoid caffeine is overly alarmist and inconsistent with the evidence,” says Grzeskowiak. “In fact, previous studies are relatively consistent in showing that small to moderate amounts of caffeine (< 200 – 300 mg day) are unlikely to harm the pregnancy. The main associations, and therefore concerns, with negative pregnancy outcomes relate to women consuming high amounts of caffeine each day.”
Andrew Shennan, from King’s College London, echoes that point saying caffeine is a prevalent dietary substance, present in a number of foods. He argues there very well may be a dose-response relationship but that doesn’t mean low doses of caffeine inherently raise the risk of negative pregnancy outcomes.
“There is, however, a dose affect i.e. the more intake the higher the harm, suggesting that caffeine is the cause of the harm, rather than just associated; however this does not necessarily imply lower doses are harmful,” says Shennan. “It is well known that women may report lower intake then actual consumption in studies and could explain why lower caffeine intake looks harmful.”
Adam Jacobs, the associate director of biostatistics at Premier Research, also points out the author of the new review may be somewhat biased on the subject, having published several articles and books in recent years discussing the “dangers” of coffee.
“I note the author has published 2 books on the dangers of coffee which in my opinion should have been included in declarations of interest for the journal article,” says Jacobs. “Overall, I think if I were a pregnant woman, I don’t think this paper would make me overly concerned about drinking the occasional cup of coffee.”
Cathy Knight-Agarwal, from the school of clinical sciences at the University of Canberra, is much less critical of James’ findings. She suggests the research raises compelling questions considering there is no nutritional need for a person to consume caffeine.
“If pregnant women cut out caffeinated products from their diet would this compromise their nutritional status and the answer is a big no,” says Knight-Agarwal. “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? Perhaps caffeine intake advice during pregnancy should mirror that of alcohol? This is a topic for further debate."
The new research was published in the journal BMJ Evidence Based Medicine.