Reference Values of Umbilical Artery Doppler Indices in Healthy Uncomplicated Pregnancy from 18-40 Week Gestation

Abstract

Background: Doppler ultrasound in second and third trimesters is non invasive method to assess fetal wellbeing and monitoring fetoplacental unit. Normal umbilical artery Doppler indices reference values have been established in Western countries but there is paucity of studies conducted in Pakistan regarding normal umbilical artery Doppler indices reference values. Objective: To evaluate the Doppler indices in the umbilical arteries of healthy pregnant women from 18-40 wks gestation. Material and Methods: A cross sectional study was conducted in Radiology department of Hayatabad Medical Complex from July 2018 to Dec 2018.Total 260 normal singleton pregnancies with gestational age ranging from 18--40 weeks were included. Doppler parameters; Resistive Index (RI), Pulsatility Index (PI) and the systolic to diastolic ratio(S/D) were recorded. Results: The normal umbilical artery Doppler indices at different gestational ages in healthy pregnant women were analyzed. Percentile values were calculated for these indices. Median values for the pulsatility index were 1.23 at 18-20 wks which reduced to 0.86 at 39-40 wks, for the resistivity index median values were 0.70 at 18-20 wks and 0.52 at 39-40 wks. Systolic/diastolic ratio was 4.16 at 18-20 wks and 2.21 at 39-40 wks. Conclusion: In normal healthy pregnancies, doppler ultrasound should be used to evaluate the degree of feto-placental blood flow in order to detect the risk of pregnancy complications. Our study results can form a baseline for Doppler indices in second and third trimester which can further help in abnormal values in high risk patients.