Maternal and fetal responses to exercise during pregnancy

Abstract

Exercise has numerous effects on the pregnant woman, the developing fetus, and the placenta. In turn, pregnancy affects the ability to perform physical activity. During pregnancy, increased metabolism at rest results almost exclusively from the gestational increase in mass. Because of this increase, a higher cardiorespiratory effort is required to perform a given amount of external work. One would expect the result to be some training effect, unless a more sedentary lifestyle is adopted. The possibility that maximal O2 consumption may increase during pregnancy has not been studied extensively, yet it is a most important variable that puts other changes in perspective. The sedentary lifestyle commonly adopted in late pregnancy in most western societies may reflect a cultural rather than a physiological phenomenon. In contrast to the physiological alterations in the mother and despite the reductions in uterine blood flow during maternal exercise, physiological changes in the fetus are small. Relatively minor changes occur in the blood concentrations of O2 and substrates during prolonged exhaustive exercise. In addition, despite a temperature increase of 1 to 2 degrees C, there is little evidence for significant alteration in fetal metabolism, cardiovascular hemodynamics, or blood catecholamine concentrations. These observations suggest that acute exercise normally does not represent a major stress for the fetus. Of course, most of the information concerning the fetus is derived from studies in experimental animals, particularly in sheep. In humans the upright position and increased uterine contractibility may affect the fetal responses differently. Virtually nothing is known about the physiological effects of exercise training on the fetus. The most likely effect may be a relatively small reduction in birth weight in some species, but this needs further investigation. Further studies are also needed for a more complete understanding of the mechanisms involved in the remarkably effective mechanisms that account for the relative homeostasis of the fetus during maternal exercise.

Calcium transport across the isolated dually perfused human placental lobule.

“…The perfusate reservoirs were mounted in a water bath at 37 +0-1 'C. The human maternal-fetal temperature gradient is about +0 5 'C (Lotgering, Gilbert & Longo, 1985) 20; Mg2+, 1-2; Ca2+, 1P4; S042-, 1-2; H2P04-, 1-2; Tris, 15-6; Glucose, 5-6; Dextran (molecular weight60000) 30 g/l. In someexperiments thiswasmodified togive Ca2+ atO l, 19, or24mM.…”

Blood Pressure and Heart Rate Responses to Sustained Static (Isometric) Contractions by Handgrip Dynamometry in Three Trimesters of Pregnancy

“…1 Exercise in pregnancy is also a stress to certain degree, causes both pressor and heart rate changes apart from other hemodynamic responses. The dual stresses of pregnancy and exercise may create enhanced physiological demands that could adversely affect pregnancy outcome.…”

Doppler sonographic evaluation of exercise-induced blood flow velocity and waveform changes in fetal, uteroplacental and large maternal vessels in pregnant women

“…Fetal heart rate (FHR) did not change. Most of the exercise studies show either no changes or a slight increase in FHR after exercise [8,22,28].…”