NEW HAVEN, Conn., Dec. 26 (UPI) -- A U.S. study in mice shows one dose of caffeine -- two cups of coffee -- ingested during pregnancy may reduce heart function for the child's lifetime.

Senior researcher Scott Rivkees of Yale University in New Haven, Conn., said while the study was done with mice, the biological cause and effect described in the research paper is plausible in humans.

"Our studies raise potential concerns about caffeine exposure during very early pregnancy, but further studies are necessary to evaluate caffeine's safety during pregnancy," Rivkees said in a statement.

The researchers studied four groups of pregnant mice under two sets of conditions for 48 hours. One group, studied in "room air," had been injected with caffeine and another injected with saline solution.

The second two groups were studied under conditions where ambient oxygen levels were halved, with one group receiving caffeine and the other receiving saline solution.

The study, published in the Federation of American Societies for Experimental Biology journal, found that under both circumstances, mice given caffeine produced embryos with a thinner layer of tissue separating some of the heart's chambers than the group that was not given caffeine.

The study also found that all of the adult males exposed to caffeine as fetuses had an increase in body fat of about 20 percent, and decreased cardiac function compared to mice not exposed to caffeine.

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