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Doppler of umbilical artery showing normalization of systolic/diastolic ratio (2.74) after starting sildenafil citrate.
Abbreviations: PSV, peak systolic velocity; EDV, end diastolic velocity; MDV, mean diastolic velocity; TAPV, timed averaged peak velocity; S/D, systolic/diastolic ratio; PI, pulsatility index; RI, resistive index; HR, heart rate.
