Maternal-fetal acute responses to two moderate-intensity exercise types: a randomized clinical trial

Abstract

Objective: This study aims to compare maternal and fetal responses during two physical exercise types. Design:A randomized clinical trial compared 120 pregnant women, gestational age of 35-37 weeks, 56 exercising on a stationary bicycle (Group A) and 64 on a treadmill (Group B). Methods:Participants were monitored for three 20-minute phases:resting, exercise and recovery. Fetal heart rate (FHR) and maternal heart rate (MHR) were monitored. Glucose and lactate levels were evaluated at rest and during exercise. Results:After the beginning of exercise, maximum lactate (L) levels were reached at 20 minutes and never exceeded 4 mmol/l. FHR decreased by 22 bpm during exercise in relation to resting values, irrespective of the exercise type (p<0.001). Comparing the exercise types, the incidence of bradycardia after 10' was 23.2% in Group A and 35.9% in Group B (p>0.05), increasing at 20' to 32% and 40.6%, respectively, (p>0.05). The FHR decrease during exercise was accompanied by a simultaneous increase in its variability (p<0.001), nevertheless a rapid return to resting values was observed shortly after exercise end. Glucose decreased in both groups irrespective of the exercise type (85 mg/dl at rest; 79 mg/dl during exercise and 81 mg/dl during recovery; p<0.001). There were no hypoglycemia cases.Conclusions: FHR variability increase and the rapid return to resting values after exercise suggests that the FHR fall and the presence of bradycardia during exercise is the fetal physiologic response to blood flow redistribution, with maintenance of fetal well-being.

Is Moderate Intensity Exercise during Pregnancy Safe for the Fetus? An Open Clinical Trial

“…The results of the present study differ from other findings, with the majority of studies reporting a lack of effect of exercise on FHR or tachycardia. 4,6,22 Possible methodological differences may explain this divergence in results, as discussed below. One limitation of those other studies was the fact that the women were evaluated prior to and following exercise, but not during exercise.…”

“…The sample size was calculated using the Open Epi software, version 2.1. Based on an incidence of fetal bradycardia of 63% detected in a group of women who initiated treadmill walking, 6 and for a power of 80% and a significance level of 5%, the total sample was calculated as 90 pregnant women.…”

“…There is also a concern with respect to the acute effects, since no consensus has yet been reached on the physiological changes in fetoplacental blood flow and the consequent fetal responses that take place during exercise, due the difficulty involved in measuring these factors. [3][4][5][6][7] Studies using animal models suggest that, during the practice of physical exercise, there is a redistribution of cardiac output, with an increase in flow to the muscles and skin and a reduction in flow to the viscera in response to the greater metabolic demand of the muscles in activity. This response also results in a reduction of $ 35% in the uteroplacental blood flow.…”