May, L., Glaros, A., Yeh, H., Clapp, J. F., & Gustafson, K. M. (2010). Aerobic exercise during pregnancy influences fetal cardiac autonomic control of heart rate and heart rate variability. Early Human Development, 86, 213-217.
Link to the abstract here
Overview: In this article, researchers were looking at the effects of moderate to vigorous cardiovascular exercise during pregnancy on the fetus, specifically heart rate (HR) and heart rate variability (HRV). Researchers followed 61 expectant mothers, 26 regularly exercising and 35 non-exercising, assessing the fetuses at 28, 32, and 36 weeks of gestation. They found that for women who exercised regularly during pregnancy, their fetus had significantly reduced HR and HRV.
I found this study interesting for the simple reason that it looks at the fetal changes as opposed to looking at strictly the benefits to the mother. The results of this study were in line with results from previously published work on this topic, an exciting confirmation for this area of research. But who really cares about that? A fetus has improved HR and HRV if the mother exercises while they are pregnant, so what?
Well, we need to be aware of how a fetus develops and at what stage in development different systems, both musculoskeletal and neurological, reach maturity. During the second and third trimesters, the parasympathetic and sympathetic nervous systems are developing, which lead to decreased fetal HR and increased HRV due to the influence these two systems exert on the heart. This change in HR and HRV is a natural process and part of the fetal development, however, during maternal exercise, there is a rise in circulating catecholamine levels that can cross the placenta. Catecholamines, such as epinephrine and norepinephrine, are essential for fetal development, including autonomic and cardiovascular developments. So we have an increase in circulating catecholamine levels, during a time in fetal development when these molecules are of increased importance to the developing fetus, so it’s quite possible that this increased exposure for the fetus actually has a pronounced effect on the development of the heart and autonomic control.
With increased control and potentially enhanced development thanks to the maternal exercising practices, we have infants being born with increased cardiovascular autonomic control, which equates to better cardiovascular health. In addition to health benefits, an increased cardiovascular capacity can carry over into sport performance and quality of life factors, assuming these benefits denote a higher “baseline” for the child. From what I have read so far, there hasn’t been any published work looking at that but I cannot imagine that will remain the case for long.
All that being said, the research here seems to indicate this; for women who are pregnant, exercise during your pregnancy. You will impart cardiovascular and autonomic nervous system benefits on your child due to the metabolic changes going on in your own body as you exercise. This can be the earliest possible form of intervention in cardiovascular health for children!