We live in the real world where pregnant people are people and shouldnt be locked in a cage of guilt for nine months
Pregnancy seems like a scary time. Not just because youre all of a sudden growing a tiny person inside you although, yes, definitely that but because there are a million people trying to terrify you with stories about otherwise-innocuous things. Sushi? Before pregnancy, its a delightful lunch. Once youre pregnant, its suddenly horrifying poison, only to be eaten if you want to die of listeria or campylobacter or some other scary-sounding disease.
Also, and I cannot stress this enough, growing a tiny person inside you.
And somehow, in the morass of nerve-wracking suggestions, we manage every once in a while to make pregnancy even scarier. This week has been a great example according to various news sources, pregnant women should stop drinking coffee entirely because even the occasional steaming brew can cause a miscarriage.
Fortunately, however, the science isnt quite as alarming as it sounds, but its not a simple issue. Get ready for some nuance.
The stories about the terror of caffeine come from a new study thats just been presented at the American Society for Reproductive Medicines annual congress. The paper itself was a relatively small epidemiological study that reanalysed an existing dataset of 1,200 pregnant women and found that any use of caffeine was associated with pregnancy loss. Since coffee is the most common way to be exposed to caffeine, the news has mostly focused on the energising beverage.
Hence the terrifying headlines warning women to cut coffee out altogether. But before we ditch the coffee bean entirely, there are a few important facts to consider.
You see, this isnt the first study on caffeine use in pregnancy. Its not even the biggest one to date several much larger studies have been done looking at this exact question before. In fact, we have enough research on the topic of whether caffeine causes pregnancy loss specifically that there have been several systematic reviews on the topic. This is a type of study whereby scientists comb through all the research that has been published on a topic to look at a subject in light of the best possible evidence, which is usually considered the strongest form of scientific evidence on a topic.
What did they find?
Well, after combining the results of more than a dozen individual studies, the systematic reviews came to slightly different answers. A study in 2015 found that even quite low intakes of caffeine were associated with increased risks of miscarriage, although the increase in risk was small. In contrast, more recent reviews from 2016 and 2017 found that low intakes of caffeine were not associated with an increased risk. Another review by the rigorous Cochrane Collaboration looked at experimental studies, where women who drank caffeine were randomised to receive either normal or decaf coffee during their pregnancy, and found no difference in outcomes between the groups.
Overall, the best evidence seems to indicate that small amounts of coffee are unlikely to cause miscarriages, although we cant rule out the risk completely. That being said, there is very good evidence that high levels of caffeine are bad for developing foetuses. Theres convincing research that lots of coffee can cause babies to have low birth weights, and very high intakes more than eight cups a day are almost certainly harmful. This has led organisations like the World Health Organization and the National Health Service in Britain to issue guidelines recommending that women limit their caffeine intake during pregnancy to 200mg about two cups of instant coffee a day. Its worth noting that the amount of caffeine in coffee is highly variable. A cup of instant coffee is pretty standardised, but espresso can have a bit less or far more caffeine in it, depending on a range of factors.
So who do we believe? The new study or the previous research?
Realistically, the new study doesnt change all that much. There are already more than a dozen individual studies looking at this topic, so the addition of a relatively small paper that hasnt even been published yet probably wont change the recommendations.
In many ways this is more about how public health works than anything we identify the ideal scenario, but make recommendations based on real life. In an ideal world, pregnant women probably wouldnt do anything even remotely unsafe, but we live in the real world where pregnant people are people and shouldnt be locked in a cage of guilt for nine months. Drinking absolutely no coffee might be the safest option, but the harms, if any, from drinking a cup or two a day seem to be extremely minimal.
If youre stressed about caffeine and pregnancy, the best advice is to talk to your doctor. They are by far the best equipped to give you advice on how to manage your way through the mammoth experience of making a human being.
And dont worry too much about the headlines. The reality is usually not nearly as scary as the stories make it seem.
Gideon Meyerowitz-Katz is an epidemiologist working in chronic disease