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How Exercise During Pregnancy Affects Your Baby’s Heart

Raphaël Büchler

Babies born to mothers who exercised during their pregnancy had healthier hearts than other infants one month postpartum, according to new research presented at the Experimental Biology 2011 meeting in Washington earlier this week, reports the New York Times.
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An earlier study led by Dr. Linda E. May, an exercise physiologist, and conducted by researchers from the Kansas City University of Medicine and Biosciences, showed that fetuses whose mothers had exercised showed slower heart rates and greater heart-rate variability (beat-to-beat variations between heartbeats), both of which are considered indicative of good heart health, when the babies’ cardiac health was measured at weeks 28, 32 and 36. Dr. May’s most recent research asked the mothers and newborns to return to the lab one month following birth, and the earlier results held true, indicating that a mother’s physical activity during pregnancy helps to shape her unborn child’s heart more permanently than was once thought.
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Dr. May’s pilot study included a group of 61 healthy women, ages 20 to 35, about half of whom had exercised regularly throughout pregnancy, jogging, power-walking or working out aerobically at a moderate pace at least thrice weekly. The other half of the group “were normally active but did not engage in formal exercise,” said Dr. May.
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While the current research is preliminary and incomplete, Dr. May plans to retest the babies from the pilot study into toddlerhood and beyond to see whether the cardiac effects continue. It is not yet known exactly how an expectant mother’s aerobic activity translates to better cardiac health for her baby, but possible explanations include certain hormones released during exercise that cross the placenta and research reported in a 2009 German study that showed fetal heart rates synchronized with the mother’s, beat for beat, when mothers-to-be were instructed to breathe fast and hard, as they would during aerobic exercise. 

Until researchers learn more about this cause-and-effect relationship, Dr. May suggested that expectant mothers who have their doctor’s approval to exercise would likely improve their baby’s heart health, should they summon the energy required for aerobic activity. 

Does this research make you more inclined to work out during pregnancy, provided you have your doctor or midwife’s okay?