Professor Jack E. James, PhD Reykjavík University Reykjavík Iceland

Maternal Caffeine Consumption and Pregnancy Outcomes Interview with:

Professor Jack E. James, PhD Reykjavík University Reykjavík Iceland

Prof. James

Professor Jack E. James, PhD
Reykjavík University
Reykjavík Iceland What prompted this study? 

Response: Chronic exposure to any chemical during pregnancy is cause for concern. There should be no exception simply because that chemical, caffeine, happens to be widely consumed. Caffeine is a habit-forming substance of no nutritional value. If anything, its widespread consumption suggests that it should be given special attention. Concern is heightened by what is known about the effects of caffeine on the human body, where it affects neural processes in the brain, including networks that control respiration and heart function.

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. Did any of the study outcomes surprise you or strike you as counter-intuitive?

Response: 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, I was not surprised that when all the findings were brought together the results pointed strongly to caffeine being a significant source of harm. Admittedly, not all human studies have reported significant associations. However, the majority of relevant peer-reviewed studies report that caffeine is associated with increased risk of negative pregnancy outcomes, including miscarriage, stillbirth, lower birth weight, small for gestational age, childhood acute leukemia, and childhood overweight and obesity. Accepting that absolute causality cannot be demonstrated here, is the connection strong enough to be convincing? 

Response: 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. Is there anything in particular that the public should be aware of about this study?

Response: It is important for the public to understand that caffeine is not the benign substance it is often portrayed to be. Unfortunately, the position of many health authorities to date has been disappointing in this regard. The idea that there is a safe level of maternal caffeine consumption is a myth that is strongly at odds with the scientific evidence. This accepting attitude towards caffeine and pregnancy must change.

Undoubtedly, larger amounts pose a greater risk than smaller amounts. This is what is referred to as a “dose-response relationship”, and that type of association is a sign that the substance, in this instance caffeine, is a cause of the outcome of interest, in this instance, negative pregnancy outcomes. In addition to this dose-response relationship, many studies report no level of caffeine consumption during pregnancy below which negative pregnancy outcomes are absent. For the wellbeing of mothers and babies, health authorities are well-overdue to take a more realistic and responsible position in relation to maternal caffeine consumption. In short, caffeine should be avoided altogether during pregnancy.


BMJ Evidence-Based Medicine

James JE “Maternal. caffeine consumption and pregnancy outcomes: A narrative review with implications for advice to mothers and mothers-to-be” BMJ Evid Based Med 2020; DOI: 10.1136/bmjebm-2020-111432. 

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Last Updated on August 25, 2020 by Marie Benz MD FAAD