COLOR DOPPLER IMAGING OF THE UTEROPLACENTAL CIRCULATION IN THE MIDDLETRIMESTER - OBSERVATIONS ON THE DEVELOPMENT OF A LOW-RESISTANCE CIRCULATION

We aimed to study the changes in the flow dynamics of the uteroplacent al and umbilical circulations in the middle trimester of normal pregna ncy, and establish normal ranges for indices of the Doppler flow, velo city waveforms (FVWs) from both circulations at 14, 18 and 24 weeks. A longitudinal study was conducted with the use of color Doppler imagin g to localize both uterine arteries and umbilical arteries and obtain FVWs from 106 healthy nulliparous women with a singleton pregnancy. Of these, 70 did not have a complicated pregnancy outcome, defined as hy pertension, growth retardation, preterm delivery or perinatal death. W e measured the resistance index (RI), pulsatility index (PI), systolic /diastolic (S/D) ratio and presence of early diastolic notching in bot h uterine arteries, and RI, PI and SID in one umbilical artery. The re sults showed a fall in all measured indices of blood flow impedance in the uteroplacental and umbilical circulations and a marked reduction in the incidence of the early diastolic notch in the uterine artery FV Ws during the mid-trimester. Our conclusion was that color Doppler ima ging allows for the accurate localization of both uterine and umbilica l arteries. Doppler FVWs then obtained confirm the development of the low-resistance uteroplacental and umbilical circulations in the mid-tr imester. Diastolic-notching is common at 14 weeks in normal pregnancy but uncommon at 24 weeks.