With the recent introduction of Doppler technology, a non-invasive methodology which enables to evaluate qualitative changes in circulatory vessels, it is possible to investigate the possible effects of various drugs on several parameters of utero-placental-fetal circulation. In the present study we evaluate the flow velocity waveform (FVW) of umbilical artery (UA) during and after administration of aminophylline, atropine and ritodrine to healthy pregnant women. In our study we did not observe any significant short-term variation of PI after the administration of these drugs. Slight variations were detected, and they may be interpreted on the basis of the mode of action of these drugs. Doppler technology may be a useful tool for monitoring some effects on the fetus of the maternal administration of therapeutic agents.