Cardiac output and uteroplacental blood flow in diet-restricted and diet-repleted pregnant rats. 
Cardiac output and uteroplacental blood flow were measured with 15 mu radioactive microspheres in anesthetized pregnant rats which were fed: (1) ad libitum throughout gestation; (2) a 50% restricted diet from day 5 of gestation; and (3) a 50% restricted diet from days 5 to 13 of gestation and ad libitum from day 14 of gestation.  An additional group of nonpregnant rats fed ad libitum was also used.  Dietary restriction caused a net maternal weight loss and a 20% reduction in mean fetal weight and mean placental weight by day 21 of gestation.  Restricted dams fed ad libitum during the last week of gestation showed a net maternal weight gain, while mean fetal weight, but not placental weight, was near that of the ad libitum--fed controls.  In the diet-restricted rats, total cardiac output was reduced 30% relative to controls by days 20 and 21 of gestation, but cardiac output per unit maternal body weight was not significantly different.  Dietary restriction decreased both total uterine and placental blood flow by about 65%.  Diet repletion late in gestation did not significantly increase total cardiac output or cardiac output per unit body weight.  Total uterine and placental blood flows were near those of controls, primarily because of an increased fraction of cardiac output distributed to the uterus.