Doppler Evidence of Intervillous Flow in the Embryonic Period

Abstract

>The characterization of the nature and time of onset of intervillous blood flow has been the subject of much recent debate. This review advances several hypotheses regarding the physiology of intervillous flow and summarizes the human and monkey evidence that currently exists. As foundational to the discussion, the historical light microscopic data is presented, and this is then coupled with illustrations from current ultrasound work that involves pulsed wave Doppler, color amplitude imaging, and color Doppler imaging. The evidence clearly suggests that intervillous flow is a normal and consistent finding in the early first trimester pregnancy.