- Abstract Objectives: To evaluate peak systolic velocimetry (PSV) in the umbilical artery (UA) among patients with single umbilical artery (SUA) as compared to patients with three vessel cords. Methods: A prospective case-control study was performed. UA blood flow velocimetry was obtained from fetuses with SUA and from a control group with three vessel cord. PSV and pulsatility index (PI) were measured. Patients' characteristics were compared for statistical differences and a linear regression model was constructed for the different groups. Results: UA Doppler velocimetry measurements were obtained from 29 patients with SUA and from 29 controls matched for gestational age. The differences between UA PI with and without SUA were significant (F=3.471; P=0.0379) showing a lower PI in the SUA group. However, no significant statistical difference was found in PSV between these two groups (F=0.149; P=0.86). Conclusions: While the impedance in the umbilical artery of patients with a SUA was lower compared to patients with a normal umbilical cord, the PSV did not differ.