Doppler flow velocity waveforms in late first- and early second-trimester fetuses: reproducibility of waveform...

The objective of the study was to assess the reproducibility of Doppler flow measurements of the fetal umbilical vein and artery, descending and ascending aorta, mitral and tricuspid valve, pulmonary artery, inferior vena cava and ductus venosus in early pregnancy. In a cross-sectional study, Doppler measurements were obtained in a total of 54 women at 11-16 weeks of gestation, at 2-5 different vascular sites, on 3-5 different occasions, at 5-min time intervals. The total variance in the various flow velocity parameters was partitioned in a between-subject and within-subject component by analysis of variance, and, from these calculations, coefficients of variation in waveform recording were calculated. Flow velocity waveform recording was characterized by coefficients of variation in the range 2.2-5.7% except for the acceleration time (18.6-24.5%) and percentage reverse flow (8.8%). In conclusion, our data suggest that fetal flow velocity waveforms in early pregnancy demonstrate good reproducibility in the individual subject, while all parameters depict larger variabilities for between-subject values. Acceleration time turned out to be poorly reproducible. If a single flow velocity waveform measurement is used for the future evaluation of clinical conditions in early pregnancy, one has to consider that normal values will display a rather wide range.