Objective To evaluate the effect of maternal isometric exercise on the placental blood flow as reflected by the velocimetric indices PI and RI derived from placental arteries.Subjects Thirty-four healthy women with normal singleton pregnancies between 22 and 35 weeks of gestation.Methods All subjects underwent an isometric handgrip exercise test. Maternal blood pressure and heart rate together with placental PI and RI were measured at rest, during the exercise and in the post-exercise recovery phase. All Doppler measurements were obtained using the Simultaneous Multigate Spectral Doppler Imaging (SM-SDI) technique, a new ultrasound modality that enables a Doppler study of multiple locations to take place within a very short time.