Gestational age effect on umbilical arterial Doppler frequency shift waveforms

Waveform panels are organized from top to bottom according to advancing gestational age. A: 16 weeks; B: 20 weeks; C: 24 weeks; D: 28 weeks; E: 32 weeks; F: 36 weeks; G: 40 weeks. Note the progressive increase in the end-diastolic velocity and the concomitant fall in the pulsatility as the gestation advances.