Doppler umbilical artery flow velocity waveforms in pregnancies complicated by major fetal malformations.

A pulse-wave Doppler ultrasound was used to identify fetal umbilical cord and to obtain flow-velocity waveforms. The umbilical artery Doppler indices were determined in 34 fetuses with major congenital malformations between 20 and 38 wks' gestation. Reference ranges of fetal umbilical artery systolic and diastolic (S/D) ratio, pulsatility index (PI) and resistance index (RI) with gestation were constructed from a cross-sectional study of 331 appropriate for gestation age fetuses of 16 to 41 wks' gestation. The records were reviewed to determine the changes associated with fetal malformation. Twenty five of 34 patients with major congenital anomalies showed high S/D ratio, PI and RI in waveforms taken from the umbilical artery. All fetuses with chromosomal aneuploidy (10 cases) had high umbilical artery S/D ratio, PI and RI. It appears that a fetal mechanism may determine the changes in the umbilical placental circulation resulting in an umbilical artery pattern of high flow resistance in fetuses with congenital anomalies.