Effect of exercise on uterine blood flow in the pregnant Pygmy goat

Abstract

Pygmy goats in the last third of pregnancy were trained to walk on a treadmill at rates up to 2.0 mph and up an inclination of 0-15 degrees. Electromagnetic flowmeters were placed unilaterally on a uterine artery, and measurements were made while the goats were standing quietly on the treadmill and during 5 min of exercise. Blood flow fell during exercise in all five animals studied, and this reduction was proportional to the level of exertion. At the highest level of exercise that these animals would voluntarily perform, uterine artery blood flow fell by 32 +/- 3 (SE) % (P less than 0.001) from control. In four additional animals the radioactive microsphere technique was used to measure uterine blood flow at rest and after 5-7 min of exercise. In these animals, exercise caused total uterine blood flow to fall by 18 +/- 10%; cotyledonary (placental) blood flow fell by 8 +/- 13%, while myoendometrial blood flow decreased by 52 +/- 12% (P less than 0.05). Thus nonplacental portions of the pregnant Pygmy goat uterus suffer major reductions in blood flow during exercise. This vasoconstriction may be due to exercise per se or to concomitant hypocapnia or hyperthermia. Singleton and twin kids born to animals that exercised were of normal birth weight.

A Prospective Study of the Association Between Vigorous Physical Activity During Pregnancy and Length of Gestation and Birthweight

“…Animal studies suggest decreased uterine blood flow during physical activity (5-8), but studies in women are inconclusive (9-11). Several studies have reported an increase in fetal heart rate during maternal physical activity (12-16), although changes in fetal heart rate may occur in response to maternal epinephrine and may not reflect a decrease in oxygen (12-15).…”

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

“…That study, however, has been criticised because it used a supine position. Although some animal experiments (ewes, goats) showed unchanged uterine blood flow [9,27], most investigations showed a decrease in uteroplacental blood flow proportional to the level and duration of exercise [6,7,18,20]. Although a drop in fetal Po 2 was noticed [6,10,21], certain compensatory mechanisms counteract the reduction in blood flow.…”

“…Although a drop in fetal Po 2 was noticed [6,10,21], certain compensatory mechanisms counteract the reduction in blood flow. These mechanisms include a redistribution a blood flow within the uterus favoring placental over nonplacental blood flow [9,18], an increase in uterine oxygen extraction and thus maintainance of uterine oxygen consumption [6,7,10] and an increase of hemoglobin and hematocrit within minutes after exercise begins, thus improving oxygen supply to the uterus [6,29]. The latter mechanism also occurs in humans within a few minutes [15], Rather difficult to interpret are our findings of a decrease in resistance in the umbilical artery.…”

Reproductive hazards in the workplace: A case study of women firefighters

“…Some animal studies have found that severe exertion during pregnancy is associated with increased fetal mortality and decreased fetal weight [Terada, 19741. The role of fetal anoxia in adverse reproduction outcomes associated with exposures is suggested by studies finding that uterine blood flow decreases with exercise [Morris et al, 1956;Hohimer et al, 1984;Clapp, 19801. However, other investigators have found no decrease in uterine blood flow with exercise [Orr et al, 19721.…”

“…However, other investigators have found no decrease in uterine blood flow with exercise [Orr et al, 19721. More significantly, several investigators have described a redistribution of uterine flow during exercise that favors the placenta, such that any decreases in uterine flow are confined to the myometrium, while placental flow is preserved [Hohimer et al, 1984;Curet et al, 19761. Voluntary exercise is well tolerated by some women during pregnancy. Collings et a1 [1983] studied women who exercised three times weekly during the second and third trimesters, attaining average heart rates of 152 beats per minute (65-70% maximum).…”