Coffee or no coffee?


"Do I need to give up coffee?" is probably one of the most common questions health professionals get asked by pregnant women. Today, they will be told that they do not need to stop drinking coffee but should limit consumption to 1-2 normal cups per day. These instructions need to be revised, according to a professor at Reykjavik University.

Dr. Jack James, professor at RU‘s Department of Psychology, has been researching the effects of coffee for years. In his latest research he wished to draw together the scientific work that has been done in this field in order to yield practical results. 

He did this by looking at 48 observational studies and meta-analyses published in the past two decades that research the relationship between coffee consumption and negative pregnancy outcomes such as miscarriage, stillbirth, preterm birth, childhood acute leukaemia, obesity and low birth weight. Altogether he researched 1.261 articles on the subject.


A man sits at a table in the coffeehouse in Sólin

A total of 42 separate findings were reported in 37 observational studies; of these 32 found that caffeine significantly increased risk of adverse pregnancy outcomes and 10 found no or inconclusive associations. Caffeine-related risk was reported with moderate to high levels of consistency for all pregnancy outcomes except preterm birth.

Eleven studies reported on the findings of 17 meta-analyses, and in 14 of these maternal caffeine consumption was associated with increased risk for four adverse outcomes: miscarriage, stillbirth, low birth weight and/or small for gestational age, and childhood acute leukaemia. The three remaining meta-analyses did not find an association between maternal caffeine consumption and preterm birth.

Our most popular drug

When consumed during pregnancy, caffeine readily crosses the placenta, exposing the fetus to the drug. Notably, the fetus is largely physically incapable of metabolising caffeine – that ability develops during the first year of life. Pregnancy studies have shown that caffeine can interfere with fetal heart function and oxygenation.

Coffee is the most popular drink in history. It effects the body in various ways, that in turn explain its popularity. It makes us feel awake and alert but is damaging to our stomach acid and contracts our veins. We get hooked on coffee and therefore, we pay a price when we quit, in the form of headaches, sleepiness and lethargy. As with other addictive substances it also has psychological effects when consumption is stopped.

„Considering what is known about the pharmacology of caffeine, the fact that the drug is widely consumed during pregnancy, and the many studies (over more than four decades) that have revealed associations between maternal caffeine exposure and negative pregnancy outcomes, it is not surpricing that when all the findings are brought together the results point strongly to caffeine being a significant source of harm.“

No safe dose

Dr. James points out that isolating coffee as the sole culprit of negative pregnancy outcomes in these cases is problematic. Is the connection strong enough to be convincing? The accumulated body of evidence is substantially consistent in implicating caffeine as a cause of harm. There have been suggestions in the literature, especially sources associated with representatives of producers of caffeine products, that the evidence of association is methodologically flawed.

However, it needs to be understood that researchers have gone to extraordinary lengths exercising the most stringent controls. As such, it is simply not plausible to suggest that current evidence implicating caffeine is so flawed as to be capable of being ignored. In fact, there is a large body of consistent evidence from well-controlled studies pointing to caffeine as a source of harm during pregnancy. Certainly, there is no evidence to suggest that caffeine benefits either mother or baby. Therefore, even if the evidence were merely suggestive, and in reality it is much stronger than that, the case for recommending caffeine be avoided during pregnancy is thoroughly compelling.

Dr. James furthermore emphasises that there is no „safe-dose“ of coffee for pregnant women. „We need to change the advice women are given and do it soon.“