Impedance cardiography helps determine whether vasoconstriction or an elevated cardiac output is occurring. The test is easy to perform and non invasive. The treatment for an elevated cardiac output in pregnancy is a beta-blocker while a vasodilator is used for vasoconstriction. If a beta-blocker is given to someone that vasoconstricted, this might make the cardiovascular parameters worse, leading to no improvement in future pregnancy issues. Likewise, if a vasoconstricting drug is given to someone with an elevated cardiac output, it could potentially make the cardiovascular parameters worse.