Objective: Umbilical artery diameters in fetuses with single umbilical artery (SUA) are known to be greater than those in fetuses with two umbilical arteries. Not all fetuses with SUA are small for gestational age (SGA). The purpose of this study was to investigate umbilical vein (UV) and umbilical artery (UA) diameters and Doppler waveforms of UA and common iliac artery according to the gestational age in fetuses with SUA and to serve an understanding of placental pathophysiology in those with SUA.
Methods: UV and UA diameters and Doppler waveforms of UA and common iliac artery according to the gestational age of 22 fetuses with SUA and with follow-up data between March 2002 and March 2010.
Results: 1) The more advanced the gestational age was, the greater the UV and UA diameters were (p<0.05). 2) The more advanced the gestational age was, the lower the ratio of peak-systolic to end-diastolic (S/D) blood flow velocities and PI in UA (p<0.05). However, the values of the S/D ratio and PI of UA were within the normal range in both the appropriate for gestational age (AGA) group and the SGA group. 3) The more advanced the gestational age was, the larger the common iliac artery diameters were (p<0.05). 4) Throughout the pregnancy, the common iliac artery without UA showed smaller diameter and higher PI than that with UA (p<0.05). 5) We found an inverse correlation between PI of the common iliac artery with UA and the gestational age and a positive correlation between PI of that without UA and the gestational age, but failed to reach any statistical significance (r= - 0.12, p>0.1 and r=0.23, p>0.1, respectively).
Conclusion: The asymmetry of arterial blood flow in the pelvis in fetuses with a SUA and normal karyotype increases with advancing gestational age. However, there might be no difference in placental circulation between fetuses with a SUA and those with two UAs because of compensatory increase in UA diameters and normal S/D ratio.