Color Doppler imaging and in vivo assessment of the anatomy and physiology of the early uteroplacental circulation

OBJECTIVE: To evaluate in vivo the anatomy and physiology of the normal early uteroplacental circulation. DESIGN: Forty-six women were included, all of whom continued their pregnancy into the second trimester. Color Doppler was used to identify peritrophoblastic flow, and spectral Doppler was used to analyze waveforms obtained from the different segments of the uteroplacental circulation. RESULTS: Flow was detected in the spiral arteries of the peritrophoblastic region in all patients. Flow was detected within the intervillous space in only one case. CONCLUSIONS: This study demonstrated that color Doppler imaging can be employed as an in vivo means of studying the uteroplacental circulation. The study confirmed the in vitro findings that trophoblastic invasion of the decidual spiral arteries occurs at 5 to 6 weeks' gestation. The study also confirmed the fact that there is no noticeable blood flow within the intervillous space during most of the first trimester of a normal pregnancy. Both of these findings may serve to protect the early gestation from the forces of arterial blood flow.