Preliminary clinical trials have shown that the non-pneumatic antishock garment (NASG), a compression device, can reverse shock, decrease blood loss, and improve maternal outcomes among women with postpartum hemorrhage. This device is designed to reverse shock by shunting blood from the lower extremities and pelvis to the vital organs. A recent study suggests an additional mechanism for the NASG in postpartum hemorrhage: the device may reduce blood loss through a direct effect on aortic blood flow in the pelvic vasculature. At present, no published studies have assessed the physiologic impact of the NASG on pelvic blood flow in patients with postpartum hemorrhage. The aim of this study was to investigate the effect of NASG application on changes in pelvic blood flow as a physiologic mechanism of action in postpartum women. The participants were 10 healthy female postpartum volunteers with no hemorrhage. A noninvasive method, Doppler ultrasound, was used to measure the resistive index (RI) of the internal iliac artery, approximating blood flow to the pelvis with and without application of the NASG. The median RI of the internal iliac artery was estimated at baseline, and with incremental and full application of the NASG. There was a significant increase from baseline values in the median RI of the internal iliac artery after full application of NASG (0.83, SD: 0.11 vs. 1.05, SD: 0.15; P = 0.02). These findings showing that application of the NASG results in a significant increase in the RI of the internal iliac artery in healthy postpartum women suggest a physiologically plausible mechanism for the reduction in blood flow by NASG application among women with postpartum hemorrhage.