Dynamics of the uteroplacental circulation in health and disease.

The relationship between the changes in the uteroplacental circulation and those occurring in the maternal systemic circulation have been discussed. The uteroplacental vascular bed acts as a low-resistance system that lowers the maternal systemic resistance and attenuates the action of vasoactive stimuli. The controlling mechanisms of the uteroplacental hemodynamics have been discussed, including the effects of the beta- and alpha-adrenergic systems. The metabolic and renal effects of the beta agonists have been listed with an appeal that they should be kept in mind when these agents are used to arrest labor. Finally, the behavior of the uteroplacental circulation during the hypertensive diseases of pregnancy has been described; the implication of these findings in the management of these diseases is emphasized.