Effects of maternal exercise on fetal breathing movements

Exercise has many benefits for adults, teens, and youngsters. It is less clear what benefit, if any, exercise may have during fetal growth during gestation. Now that scientists have determined that, generally speaking, maternal exercise poses no significant risk to a fetus, studies are underway to examine the mother/fetus/exercise/health connection. One important study is now complete. Entitled The Effects of Maternal Exercise on Fetal Breathing Movements, it was conducted by Stephanie Million and Linda E. May, Kansas City University of Medicine and Biosciences (KCUMB), Kansas City, MO; and Kathleen M. Gustafson, University of Kansas Medical Center (KUMC), Kansas City, KS. The researchers will discuss their findings at the 122nd Annual Meeting of the American Physiological Society (APS; www.the-aps.org/press), which is part of the Experimental Biology 2009 scientific conference. The meeting will be held April 18-22, 2009 in New Orleans.

Study and Background

The primary aim of the pilot project was to test the theory that maternal exercise imparts a cardiovascular benefit to the fetus. The secondary aim was to determine if exercise-exposed fetuses have increased breathing movements compared to non-exercise exposed fetuses. Fetal breathing movements are a marker of fetal well-being and reflect functional development of the respiratory system and central nervous system control.

The researchers used a non-invasive, dedicated fetal biomagnetometer to measure maternal and fetal magnetocardiograms (MCG) along with fetal movements (breathing, body movements, hiccups and non-nutritive suck). Unlike an ultrasound, which takes static measurements of anatomy, MCG records the physiology of the developing fetus.

The investigators looked at the results from pregnant women between 20 and 35 years of age. The mothers were classified as exercisers if they performed moderate intensity aerobic exercise at least 30 minutes three times per week (moderate to vigorous walking, stationary bicycling and running). Mothers in the control category did not partake of a regular exercise routine. The MCG was measured between 24-36 weeks gestational age.

Between 36-38 weeks gestational age, breathing movements were identified using specific criterion. Measures of fetal heart rate and autonomic control were analyzed during episodes of fetal breathing and non-breathing movements. Although there was no difference in the number of breathing episodes, differences were noted between the groups.

Results

The researchers found:

• Fetal HR 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.
• Three independent measures of vagal control were higher in the exercise-exposed fetuses during breathing movements.
• During periods of fetal non-breathing, there were no significant differences in measures of vagal control between groups. There were no group or breathing period differences in sympathetic heart rate control.

Conclusion

According to Drs. May and Gustafson, "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." Their next step is to use exercise as a potential intervention to improve short and long term outcomes in children born to women at risk for gestational diabetes.

Source: American Physiological Society