April 17 (HealthDay News) -- Exercising during pregnancy appears to boost fetal development, according to a U.S. study.

The study included pregnant women, ages 20 to 35, who were divided into two groups. Those in the exercise group did moderate intensity aerobic exercise for at least 30 minutes three times per week. Those in the control group did not get regular exercise.

A team at the Kansas City University of Medicine and Biosciences and the University of Kansas Medical Center used non-invasive tests to monitor fetal development, breathing and body movements, as well as fetal heart rate and autonomic nervous system control.

The main aim of the study was to determine whether exercise during pregnancy resulted in cardiovascular benefits to the fetus. The secondary goal was to determine if exercise during pregnancy increasing fetal breathing movements, a marker of well-being and of functional development of the respiratory system.

The study found that:

• Fetal heart rate was significantly lower in the exercise group during both breathing and non-breathing movement periods.
• Fetal short-term and overall heart rate variability were higher in the exercise group during breathing movements.
• The exercise-exposed fetuses had higher measures of vagal (cardiovascular) control during breathing movements.
• No significant differences in measures of vagal control between the two groups were noted during periods of fetal non-breathing, and there were no group or breathing differences in sympathetic heart rate control.

"These findings suggest a potential benefit of maternal exercise on fetal development because of the link between fetal breathing movements and the developing autonomic nervous system," concluded the researchers.

The study was expected to be presented at the annual meeting of the American Physiological Society, April 18-22, in New Orleans.

SOURCE: American Physiological Society, news release, April 17, 2009