Doppler waveform patterns and reference ranges of fetal renal artery blood flow indices in normal Thai fetuses during the second trimester

Abstract

Abstract Background Fetal hemodynamics can be assessed by Doppler ultrasonography, but the normal Doppler waveform pattern and reference range of fetal renal artery blood flow indices in normal Thai fetuses during the second trimester have not been studied. Objectives To study the pattern and establish the normal reference range of fetal renal artery blood flow indices in the normal Thai fetus during the second trimester. Materials and methods This cross-sectional descriptive study included 512 normal singleton pregnant women, gestational age between 14(+0) and 28(+6) weeks. Ultrasonography was performed to assess the Doppler waveform pattern and estimate the normal reference range of fetal renal artery blood flow indices. All fetuses were delivered at term with normal outcomes at birth. The mean and 95th and 5th percentiles of the Doppler indices for each gestational week were estimated. Results Doppler patterns with absence of diastolic flow in the entire cardiac cycle (type I), and absence of diastolic flow at the end of cardiac cycle (type II) were presented in about 10.4% of normal fetuses during the second trimester of pregnancy. Values for pulsatility index, peak systolic velocity, systolic-to-diastolic ratio, and resistance index (with absent end-diastolic velocity (AEDV) removed) each increased significantly with gestational age. The increase in end-diastolic velocity (with AEDV removed) with gestational age was not significant. Conclusion These normative data could serve as a basis for evaluation of the fetal renal artery blood flow, which should be of benefit for pregnancy management, especially in situations that interfere with fetal renal perfusion.