Objective: To assess the pharmacodynamic effects of furosemide in pregnancy. Methods: Twenty-one pregnant women who received furosemide 20 mg daily had cardiac output (CO), stroke volume (SV), and total peripheral resistance (TPR) measured by Doppler technique before and after treatment. Results: Furosemide was initiated at 22.4 ± 6.0 weeks gestation. CO and SV decreased (mean ± SD: 1.2 ± 0.2 L/min and 17±3 mL, respectively), whereas TPR increased (101±26 dyne·sec·cm^-5; p < 0.001 for all) after 2.9±1.4 weeks. Hemodynamics did not approach the expected mean for pregnancy. Conclusions: While furosemide improved the hyperdynamic circulation in pregnancy, it did not lower blood pressure or cause clinically significant vasoconstriction.