"Our studies raise potential concerns about caffeine exposure during very early pregnancy, but further studies [in humans] are necessary to evaluate caffeine's safety during pregnancy," said Scott Rivkees, Yale University's associate chair of pediatric research and a senior participant in the research.
The experiment involved four groups of pregnant mice, two of which were examined in "room air" and two in air with a 50 percent reduction in oxygen content. Among the room air groups, one was injected with a mild dose of caffeine and the other with saline solution, a standard dilute solution of table salt. The lower-oxygen groups were treated in the same way %u2013 one receiving caffeine and other saline.
The result was that mice in both caffeine groups produced embryos with abnormally thin tissue between some heart chambers compared with the saline-only groups. The researchers also found significant differences in the offspring of the caffeine versus saline groups.
Specifically, the young of the caffeinated mothers had a 38 percent worse heart function than those in the saline groups, and the males in the caffeine groups had 20 percent more body fat than their saline-group counterparts.
"Caffeine is everywhere: in what we drink, in what we eat, in pills that we use to relieve pain, and even in candy," said Gerald Weissmann, editor in chief of The FASEB Journal. "This report shows that, despite popular notions of safety, there's one place it probably shouldn't be: in the diet of an expectant mother."