Exercise During Pregnancy Fetal Responses to Current Public Health Guidelines

Department of Gynecology and Obstetrics, Division of Maternal-Fetal Medicine, Johns Hopkins University School of Medicine, Johns Hopkins Bayview Medical Center, Baltimore, Maryland 21224, USA.
Obstetrics and Gynecology (Impact Factor: 5.18). 03/2012; 119(3):603-10. DOI: 10.1097/AOG.0b013e31824760b5
Source: PubMed


To evaluate acute fetal responses to individually prescribed exercise according to existing guidelines (U.S. Department of Health and Human Services) in active and inactive pregnant women.
Forty-five healthy pregnant women (15 nonexercisers, 15 regularly active, 15 highly active) were tested between 28 0/7 and 32 6/7 weeks of gestation. After a treadmill test to volitional fatigue, target heart rates were calculated for two subsequent 30-minute treadmill sessions: 1) moderate intensity (40-59% heart rate reserve); and 2) vigorous intensity (60-84%). All women performed the moderate test; only active women performed the vigorous test. Fetal well-being measures included umbilical artery Dopplers, fetal heart tracing and rate, and biophysical profile. Measures were obtained at rest and immediately postexercise.
Groups were similar in age, body mass index, and gestational age. Maternal resting heart rate in the highly active group (61.6 ± 7.2 beats per minute [bpm]) was significantly lower than the nonexercise (79.0 ± 11.6 bpm) and regularly active (71.9 ± 7.4 bpm) groups (P<.001). Treadmill time was longer in highly active (22.3 ± 2.9 minutes) than regularly active (16.6 ± 3.4) and nonexercise (12.1 ± 3.6) groups (P<.001), reflecting higher fitness. With moderate exercise, all umbilical artery Doppler indices were similar pre-exercise and postexercise among groups. With vigorous exercise, Dopplers were similar in regularly and highly active women with statistically significant decreases postexercise (P<.05). The group × time interaction was not significant. Postexercise fetal heart tracings met criteria for reactivity within 20 minutes after all tests. Biophysical profile scores were reassuring.
This study supports existing guidelines indicating pregnant women may begin or maintain an exercise program at moderate (inactive) or vigorous (active) intensities.

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    • "In the absence of obstetric complications, moderate exercise during pregnancy is generally considered safe and poses no known risk to the fetus [1] [2] [3] [4] [5] [6] [7] [8]. Epidemiological data suggest that regular physical activity throughout pregnancy improves maternal cardiovascular function [3], limits weight gain and fat retention [9], improves insulin resistance and metabolic control [9] [10] [11], prevents the onset of gestational diabetes mellitus [12] [13], reduces the incidence of operative delivery [14], and decreases depressive symptoms in the postnatal period [15] [16]. "
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    ABSTRACT: Previously, we reported that regular maternal aerobic exercise during pregnancy was associated with lower fetal heart rate (HR) and higher heart rate variability (HRV) at 36weeks gestation. We now report the effect of maternal exercise on infant HR and HRV in subjects who remained active in the study at the one-month follow up visit. We aimed to determine whether differences in fetal cardiac autonomic control related to maternal physical activity were an in utero phenomenon or would persist 1month after birth. Magnetocardiograms (MCGs) of infants born to regularly exercising (≥30min of aerobic activity, 3 times per week; N=16) and non-exercising (N=27) pregnant women were recorded using a fetal biomagnetometer. Normal R-peaks were marked to derive infant HR and HRV in time and frequency domains, including the root mean square of successive differences (RMSSD), the standard deviation of normal-to-normal interbeat intervals (SDNN), and power in the low frequency (LF) and high frequency (HF) bands. Group differences were examined with Student's t-tests. Infants born to exercising women had significantly higher RMSSD (P=0.010), LF power (P=0.002), and HF power (P=0.004) than those born to women who did not engage in regular physical activity while pregnant. Infants born to women who participated in regular physical activity during pregnancy continued to have higher HRV in the infant period. This suggests that the developing cardiac autonomic nervous system is sensitive to the effects of maternal physical activity and is a target for fetal programming.
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