Mice Study Shows Caffeine in Pregnancy Affects Cardiac Function of Offspring

December 29, 2008

December 29, 2008 (New Haven, CT ) — A new study in mice indicates that the ingestion of caffeine during pregnancy adversely affects fetal heart development and results in reduced cardiac output when the offspring grow up.[1] The amount of caffeine given to the mice was the equivalent of just two cups of coffee a day for humans, say Dr Christopher C Wendler (Yale University School of Medicine, New Haven, CT) and colleagues in their paper published online December 16, 2008 in the FASEB Journal, the publication of the Federation of American Societies for Experimental Biology.

"The take-away is that we saw [adverse] effects of caffeine, not just for the development of the embryo but potentially for the long term. Using specially calibrated echocardiography, we saw reductions in the cardiac function of the exposed embryos after they were born and had reached young adulthood," Wendler told heartwire .

He stressed, however, that these observations in mice may not be directly relevant to human health and that further studies are needed to assess the effects and safety of caffeine exposure during pregnancy.

Nevertheless, given that caffeine exposure in humans during early pregnancy has already been associated with an increased risk of miscarriage and also recently with fetal growth restriction,[2] "this is one more indication that it might be a good idea to restrict caffeine-containing drinks during pregnancy," Wendler said.

35% reduction in cardiac output in mice exposed to caffeine

In their experiment, Wendler and colleagues studied four groups of pregnant mice for 48 hours. The first two groups were studied in "room air," with one group receiving caffeine injections of 20 mg/kg and the other saline injections. The other two groups were studied under hypoxic conditions--as the researchers were also examining the effects of hypoxia on embryonic development--and again one group got caffeine and the other saline.

Wendler said the injections were given on around day 8 of the gestation period, which is a total of 21 days in mice, so day 8 is equivalent to the first trimester. Caffeine and its metabolites are easily transferred across the placenta, with embryonic concentrations being just slightly lower than maternal levels, he and his colleagues explain.

Caffeine exposure that may seem modest to the mother may be much more significant for the embryo.

But although caffeine is normally metabolized quickly via demethylation, the fetus is unable to demethylate caffeine, they point out. "Thus, caffeine exposure that may seem modest to the mother may be much more significant for the embryo."

After the mice were born, at the age of around 10 weeks--which equates to young adulthood--the researchers assessed the cardiac function of the mice using echocardiography with a more sensitive probe (of a higher frequency, which gave better resolution in the mice). They discovered that those who had been exposed to the caffeine in utero had, on average, 35% lower cardiac function and changes in wall thickness compared with the mice that had not been exposed to caffeine.

There was a small effect of the hypoxic environment on cardiac function, but it was not as strong as the effect of the caffeine, Wendler told heartwire .

Senior author Dr Scott A Rivkees (Yale University School of Medicine, New Haven, CT) summarized the findings for heartwire : "Our studies raise potential concerns about caffeine exposure during very early pregnancy, but further studies are necessary to evaluate caffeine's safety during pregnancy."

  1. Wendler CC, Busovsky-McNeal M, Ghatpande S, et al. Embryonic caffeine exposure induces adverse effects in adulthood. FASEB J 2008; DOI: 10.1096/fj.08-124941. Available at: https://www.fasebj.org. Abstract

  2. CARE Study Group. Maternal caffeine intake during pregnancy and risk of fetal growth restriction: a large prospective observational study. BMJ 2008; 337:a2332. Available at: https://www.bmj.com/cgi/content/full/337/nov03_2/a2332. Abstract

The complete contents of Heartwire , a professional news service of WebMD, can be found at www.theheart.org, a Web site for cardiovascular healthcare professionals.

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