A new study links caffeine consumption by pregnant women with reduced birth weight in their offspring. For each 100 milligrams of caffeine consumed daily, as recorded in daily food diaries, the newborn on average had a birth weight between three quarters to an ounce lower than women who ingested no caffeine. (A 16 oz. cup of Starbucks Pike Place Roast has 330 mgs of caffeine, according to Starbucks website).
Published in the journal BMC Medicine, the observational study involved tracking the caffeine intake of 60,000 pregnant Norwegian mothers over a 10-year period. The correlation remained even after excluding smokers from the analysis.
ACSH s Dr. Gilbert Ross says moms-to-be who had some java this morning shouldn t be needlessly alarmed. There s a lot of mythology around coffee and tea during pregnancy, he says. Even if this study s findings are confirmed on better prospective trials, the worst case scenario impact is very small. I would advise women not to be needlessly concerned about their coffee intake although I wouldn t want to make an authoritative statement about five or six cups a day.
ACSH s Dr. Josh Bloom says that because of its chemical and pharmacological properties, caffeine will easily pass through the placenta and expose the fetus to some undetermined concentration of the drug. Whether this actually has an adverse effect is not known, but given the mechanism by which caffeine works as a drug, even theoretical concerns are not unreasonable in this instance.