ObjectiveTo compare resistance index (RI) and pulsatility index (PI) in the spiral and intervillous arteries, and peak systolic velocity of the continuous intervillous flow in normal and abnormal first-trimester pregnancy.MethodsTransvaginal color and pulsed Doppler were used in a prospective analysis of 60 normal (controls) and 54 abnormal (30 missed abortions and 24 anembryonic) pregnancies (6–12 weeks' gestation). Repeated-measures analysis of variance was used for comparison between groups.ResultsA gradual decrease in spiral artery RI and PI was found in women with anembryonic pregnancies. No difference in spiral artery impedance was noted in women with normal pregnancies, but there was a progressive increase in spiral artery RI and PI in women with missed abortion. A significant increase in continuous intervillous blood flow velocity was noted from the 11th week onward in the normal pregnancy group (8.0 ± 0.9 versus 12.2 ± 1.4 cm/second). Intervillous arterial blood flow signals did not demonstrate any difference in RI and PI with advancing gestational duration. Significantly lower PI values were obtained from the intervillous arteriesw in women with anembryonic pregnancy (PI 0.54 ± 0.04) than in controls (PI 0.80 ± 0.04) and those with missed abortions (PI 0.75 ± 0.04). However, there was no statistically significant difference in the intervillous RI between subgroups.ConclusionThe new generation of sensitive Doppler units can detect intervillous flow as a continuous progressive process during the first trimester of normal and abnormal pregnancy. There is a significant difference in intervillous artery vascular impedance between normal and anembryonic pregnancies.