TUESDAY, April 8 (HealthDay News) -- Exercise does a body good -- two bodies when the one exercising is a pregnant woman.

A new study shows that when a mom-to-be works out, her fetus reaps cardiac benefits. The benefits show up as lower fetal heart rates, according to the finding to be presented this week at the Experimental Biology 2008 annual meeting in San Diego.

"This study suggests that a mother who exercises may not only be imparting health benefits to her own heart, but to her developing baby's heart as well. As a result of this pilot study, we plan to continue the study to include more pregnant women," study co-author Linda E. May, of the Department of Anatomy at Kansas City University of Medicine and Biosciences, said in a prepared statement.

Ten women participated in the study, half of whom were exercisers and the other half who weren't. Fetal movements such as breathing, body and mouth movements were monitored and recorded from 24 weeks into pregnancy to term.

The researchers found significantly lower heart rates among fetuses that had been exposed to maternal exercise throughout the study period. The heart rates among the fetuses not exposed to exercise were higher, regardless of the fetal activity or the gestational age.