The American College of Obstetricians and Gynecologists recommends limiting caffeine consumption during pregnancy to 200 milligrams a day, or roughly 12 ounces of coffee, but a new review of studies suggests that no caffeine at all may be safer.
The analysis included 37 observational studies and meta-analyses that reported caffeine’s effect on six negative pregnancy outcomes: miscarriage, still birth, low birth weight or small for gestational age, preterm birth, childhood acute leukemia, and having a child who is overweight or obese.
The report, in BMJ Evidence-Based Medicine, found that caffeine consumption was associated with all of these negative outcomes except preterm birth. Findings for stillbirth were consistent across studies, with risks increasing from twofold to fivefold. Of 10 studies of low birth weight, seven reported an increased risk with increasing caffeine consumption. Three meta-analyses found that maternal caffeine consumption is associated with an increased risk for childhood acute leukemia, and eight of nine studies reported an association of caffeine with miscarriage.
The studies are observational and do not prove cause and effect, but the author, Jack E. James of Reykjavik University in Iceland, said that the accumulated body of evidence for harm is substantial.
“Even if the evidence were merely suggestive, and in reality it is much stronger than that,” he said, “the case for recommending caffeine be avoided during pregnancy is thoroughly compelling.”