Pregnant women receive all sorts of advice on what to do or not do during pregnancy. For years medical guidelines in both the US and Europe have been that moderate (up to 200 mg) ingestion of caffeine during pregnancy is OK, which means about 2 cups of regular coffee a day.
However, a recent review of studies by Reykjavik University Professor Jack E. James found that ingesting caffeine during pregnancy is linked to health problems and that there is no safe level during pregnancy. In other words, caffeine and caffeinated beverages should be avoided during pregnancy and when trying to conceive.
Health problems associated with caffeine intake during pregnancy are miscarriage, stillbirth, low birth weight and/or small for gestational age, childhood leukemia, and childhood overweight and obesity. Studies typically found a dose-response effect - the more caffeine is ingested, the more negative health effects.
Human studies looking at this issue are observational, but negative health effects are supported by animal research going back more than four decades. Caffeine crosses the placenta and goes to the baby. Negative health effects occur because the fetus can not clear the caffeine well because it lacks an enzyme that metabolizes caffeine.
Professor James points out that the industry established and funded the group ILSI (International Life Sciences Institute) which successfully fought any FDA warnings about caffeine and pregnancy, and which attacked any research suggesting it could be harmful to pregnancy or the fetus. [Why am I not surprised about the success of the industry group? And that they published their own "research" showing caffeine was benign in response to scientific research showing negative health effects.]
Excerpts from Science Daily: No safe level of caffeine consumption for pregnant women and would-be mothers
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 published in BMJ Evidence Based Medicine.
Pregnant women have been advised that consuming a small amount of caffeine daily will not harm their baby. The UK 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.
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 leukemia, 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 leukemia. The three remaining meta-analyses did not find an association between maternal caffeine consumption and preterm birth.
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.
Professor 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 leukemia and childhood overweight and obesity, but not preterm birth.