Women who are pregnant or trying to conceive should be advised to avoid caffeine because the evidence suggests that maternal caffeine consumption is associated with negative pregnancy outcomes and that there is no safe level of consumption, finds an analysis of observational studies.
Caffeine is probably the most widely consumed psychoactive substance in history, and many people, including pregnant women consume it on a daily basis.
Pregnant women have been advised that consuming a small amount of caffeine daily will not harm their baby. The UK National Health Service (NHS), the American College of Obstetricians and Gynecologists, the Dietary Guidelines for Americans and the European Food Safety Authority (EFSA) set this level at 200 mg caffeine, which approximates to roughly two cups of moderate-strength coffee per day.
This study undertook a review of current evidence on caffeine-related pregnancy outcomes, to determine whether the recommended safe level of consumption for pregnant women is soundly based.
Through database searches, Professor Jack James, of Reykjavik University, Iceland, identified 1,261 English language peer-reviewed articles linking caffeine and caffeinated beverages to pregnancy outcomes.
These were whittled down to 48 original observational studies and meta-analyses published in the past two decades reporting results for one or more of six major negative pregnancy outcomes: miscarriage, stillbirth, low birth weight and/or small for gestational age, preterm birth, childhood acute leukaemia, and childhood overweight and obesity.
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.
No meta-analyses looked at the association between maternal caffeine consumption and childhood overweight and obesity, but four of five observational studies reported significant associations.
This is an observational study, so can’t establish causation, and the author points out that the results could be impacted by other confounding factors, such as recall of caffeine consumption, maternal cigarette smoking and most importantly pregnancy symptoms. Pregnancy symptoms such as nausea and vomiting in early pregnancy are predictive of a healthy pregnancy and women who experience them are likely to reduce their caffeine intake.
But he adds that the dose-responsive nature of the associations between caffeine and adverse pregnancy outcomes, and the fact some studies found no threshold below which negative outcomes were absent, supports likely causation rather than mere association.
James concludes that there is “substantial cumulative evidence” of an association between maternal caffeine consumption and diverse negative pregnancy outcomes, specifically miscarriage, stillbirth, low birth weight and/or small for gestational age, childhood acute leukaemia and childhood overweight and obesity, but not preterm birth.
As a result, he adds, 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,” he says.
Abstract
Objectives: Caffeine is a habit-forming substance consumed daily by the majority of pregnant women. Accordingly, it is important that women receive sound evidence-based advice about potential caffeine-related harm. This narrative review examines evidence of association between maternal caffeine consumption and negative pregnancy outcomes, and assesses whether current health advice concerning maternal caffeine consumption is soundly based.
Methods: Database searches using terms linking caffeine and caffeinated beverages to pregnancy outcomes identified 1261 English language peer-reviewed articles. Screening yielded a total of 48 original observational studies and meta-analyses of maternal caffeine consumption published in the past two decades. The articles reported results for one or more of six major categories of negative pregnancy outcomes: miscarriage, stillbirth, low birth weight and/or small for gestational age, preterm birth, childhood acute leukaemia, and childhood overweight and obesity.
Results: Of 42 separate sets of findings reported in 37 observational studies, 32 indicated significantly increased caffeine-related risk and 10 suggested no or inconclusive associations. Caffeine-related increased risk was reported with moderate to high levels of consistency for all pregnancy outcomes except preterm birth. Of 11 studies reporting 17 meta-analyses, there was unanimity among 14 analyses in finding maternal caffeine consumption to be associated with increased risk for the four outcome categories of miscarriage, stillbirth, low birth weight and/or small for gestational age, and childhood acute leukaemia. The three remaining meta-analyses were also unanimous in reporting absence of a reliable association between maternal caffeine consumption and preterm birth. No meta-analyses were identified for childhood overweight and obesity, although four of five original observational studies reported significant associations linking maternal caffeine consumption to that outcome category.
Conclusions: The substantial majority finding from observational studies and meta-analyses is that maternal caffeine consumption is reliably associated with major negative pregnancy outcomes. Reported findings were robust to threats from potential confounding and misclassification. Among both observational studies and meta-analyses, there were frequent reports of significant dose–response associations suggestive of causation, and frequent reports of no threshold of consumption below which associations were absent. Consequently, current evidence does not support health advice that assumes 'moderate' caffeine consumption during pregnancy is safe. On the contrary, the cumulative scientific evidence supports pregnant women and women contemplating pregnancy being advised to avoid caffeine.
Authors
Jack E James
[link url="https://www.bmj.com/company/newsroom/no-safe-level-of-caffeine-consumption-for-pregnant-women-and-would-be-mothers/"]BMJ material[/link]
[link url="https://ebm.bmj.com/content/early/2020/07/28/bmjebm-2020-111432"]BMJ Evidence Based Medicine abstract[/link]