The influence of the site of Doppler recording on umbilical artery pulsatility index during the first trimester.

The aim of our study was to determine the pulsatility index (PI) of the umbilical artery velocity waveform obtained from the fetal insertion, the placental insertion and a free floating loop of the umbilical cord. This was a prospective study involving 60 consecutive singleton pregnancies undergoing ultrasound examination between 10 and 13 weeks' gestation. Doppler measurements were obtained transvaginally from the placental and the fetal abdominal insertion, and from a free floating loop of umbilical cord. Chromosomal abnormalities and structural malformations detected by ultrasound were excluded. A multi-way analysis of variance did not show significant differences between the measurements of umbilical PI at the different sites of the umbilical cord and Pearson's coefficient showed an excellent correlation between them. No significant intra- and interobserver differences were found. In conclusion, measurements of Doppler velocimetric indices of the umbilical artery during the first trimester are not influenced by the recording site and these recordings are reproducible at this stage of gestation.