Abstract

Introduction: There is a critical need to determine a standard site sampling along the umbilical cord that has acceptable reliability and validity to measure the umbilical artery indexes. This study aimed to assess the correlation of the placental insertion site of the cord with the free loop in terms of umbilical artery indices including pulsatility index (PI), resistance index (RI), and systolic/diastolic ratio (S/D).

Methods: This cross-sectional study was conducted on 150 singleton fetuses of 28 to 40 weeks of gestational age in the prenatal clinics of Imam Khomeini hospital from January 2019 to January 2021.

Results: Analyses of data have shown that there were not any significant correlations between the means of Doppler indices of UA with sex of fetus (P>0.05) or the number of mother's gravid (P>0.05).

There was a positive significant association between PI, RI, and S/D of the umbilical artery in the free loop of umbilical cord and placenta site after adjusting for gestational age group, fetus weight, and placenta position.

Conclusion: It seems the placenta site Doppler, considering its acceptable correlation with the free loop and its reliability, can also be a good choice as a standard sampling site for fetuses' circulation assessment especially in multiple pregnancies and fetuses with oligohydramnios.

Keywords: Resistance index, Pulsatility index, Systolic/diastolic ratio, Free-loop Doppler, Placenta insertion Doppler, Umbilical cord