In 9 experimental rabbit fetuses (with reduced uterine-placental blood frow), noradrenaline administration led to an obvious thermogenic response and heart rate increase, but not in intact rabbits. Obviously the noradrenaline dosage corresponds to the range of adaptive capacities of the functional systems in intact fetuses and so does not induce any shifts of the homeostasis parameters in them. The experimental fetuses prove to be more vulnerable to stresses, and homeostasis parameter shifts in them are statistically significant.