Intra-abdominal versus free-loop portion Doppler analysis of the umbilical artery: the importance of the choice.

AIM

The aim of this study was to assess the variations in Doppler indexes along the length of the cord from the intra-abdominal portion (IAP) to the free loop portion (FLP) of the umbilical artery (UA).

METHODS

UA blood flow velocities were measured at the IAP and FLP in 100 low-risk singleton pregnancies. The peak systolic velocity (PSV), end-diastolic velocity, pulsatility index (PI), resistance index (RI), PS/ED ratio and Delta value (Δ) were calculated. at each site of sampling and were compared.

RESULTS

PI and RI of the IAP were greater versus the FLP. UA blood velocities increased with gestational age and the PSV at the IAP showed different development compared to other sites, increasing from 20 to 30-32 weeks and then decreasing until term. The PSV value was greater in the IAP from 20 until 36 weeks. There were not significant differences in EDV values between the two sites. The Δ PI in IAP remained constantly greater than ~0.2 at all gestational ages.

CONCLUSION

UA Doppler parameters vary significantly at different locations, showing the greater value in the IAP. The IAP site is in a fixed anatomical position, therefore potentially reproducible. This potential advantage is very important in cases of severe growth restriction and in monoamniotic twins.