1ST-TRIMESTER UTEROPLACENTAL AND FETAL BLOOD-FLOW VELOCITY WAVE-FORMSIN NORMALLY DEVELOPING FETUSES - A LONGITUDINAL-STUDY

Our objectives were to obtain a complete overview of uteroplacental an d fetal hemodynamics early in pregnancy and to record flow velocity wa veforms in the vitelline artery using color Doppler equipment. Flow ve locity waveforms were recorded in 18 uneventful pregnancies between 6 and 16 weeks of gestation. Doppler recordings were made of the left an d right uterine and spiral arteries from 6 weeks of gestation onwards. Recordings of the umbilical artery, fetal aorta and fetal cerebral ar teries started in weeks 7, 8 and 9, respectively. Where possible, the vitelline arteries were also recorded. The resistance and pulsatility indices and 95% confidence intervals for predictions were calculated. For the uterine and spiral arteries, characteristics of the waveforms were assessed. The resistance index of both uterine and spiral arterie s gradually decreased with advancing pregnancy. For the umbilical arte ry, aorta and cerebral artery, the earliest possible Doppler recording s and characteristics of the waveforms were established. The pulsatili ty index of the umbilical arteries and fetal aorta showed a sharp decr ease towards the 16th week. The pulsatility index of the fetal cerebra l artery showed only a mild decrease towards week 16. In a longitudina l analysis, there were significant changes of the resistance and pulsa tility indices for each patient. In the vitelline artery, recordings w ere possible in eight out of 18 fetuses, and only in weeks 7 and 8 of gestation. The pulsatility index showed a wide range and was not depen dent on menstrual age. Knowledge of the normal flow velocity waveforms in the maternal uteroplacental and fetal circulations early in pregna ncy may lead to a better understanding of physiological mechanisms.