A big issue in assessment of placental abnormalities in vivo is that the placenta has two separate blood supplies, maternal and fetal. Presently, there are no easy ways to directly assess these contributing flows at the same time. If there were such a method, it could greatly enhance placental evaluation in a myriad of ways. For instance, it would be possible to show the effects of various therapies on both the maternal and fetal sides of the placental circulation. We have been able, in a preliminary way, to detect the effects of both the maternal and fetal arterial inputs on the envelope of the umbilical venous signal using the fast Fourier Transform. In a retrospectively analyzed set of umbilical venous Doppler spectra, we could distinguish between high risk and normal gestations by comparing the maternal and fetal contributions to this signal. The measure is very simple to perform, and could be a very easy way to assess maternal and fetal contributions to placental flow.