Fetal renal artery blood flow – Normal ranges

Abstract

Introduction The study objectives were to develop standard charts for fetal renal artery blood flow to define normal ranges and to assess the reliability of the measurements. Methods This prospective, longitudinal study reviewed 72 low-risk singleton pregnancies who had serial ultrasound examinations. Pulse wave Doppler was used to obtain the resistivity and pulsatility indices of the fetal renal arteries. Standard charts of the fetal renal arteries were created using mixed effects modelling and the intra- and interobserver reliability for the renal blood flow measurements was analysed. Results Standard charts of the normal ranges of the renal artery resistive index (RI) and pulsatility index (PI) of the fetal renal arteries were created. The 3rd, 5th, 10th, 50th, 90th, 95th and 97th centiles were calculated. The intraclass correlation coefficient was acceptable for intraobserver reliability (RI = 0.66, PI = 0.88) and poor for interobserver reliability (RI = 0.11, PI = −0.56). Conclusions These novel charts demonstrate the change of the fetal renal artery blood flow during pregnancy. These may be used in clinical practice to detect variations from these normal ranges and be useful in future studies of kidney function projection.