Comparison of Doppler sampling locations in the umbilical artery for detecting fetal growth restriction

Objectives The objectives of study were to determine the most reliable umbilical artery (UA) Doppler sampling location for detecting fetal growth restriction (FGR) and compare indices between growth-restricted and adequate for gestational age (AGA) fetuses. Methods UA Doppler was done in 55 pregnant women with FGR and 120 with AGA and indices were recorded at three locations including fetal end, free-floating portion (FFL) and placental end (PE). Receiver Operating Curve (ROC) analysis was performed to find out the accuracy of the Doppler indices for detecting FGR. Measurements at three portions of UA were compared with each other using repeated measures ANOVA in normal pregnancies. Results The sensitivity for differentiating AGA from FGR using pulsatility index (PI) was the same (94.5%) at all three locations. The specificity was highest at fetal end (FE) using PI values (99.2%) as well as for systolic to diastolic (S/D) ratio (100%). Likewise, sensitivity and specificity both were highest (89.1% and 99.2% respectively) at FE when resistive index (RI) was used for this differentiation. Conclusion Although UA Doppler is a well-known non-invasive method used for investigating fetoplacental circulation, indices taken at fetal-end of UA are more reliable in diagnosing cases of FGR which might be due to it being a fixed site.