Longitudinal reference intervals for Doppler velocimetric parameters of the fetal renal artery correlated with amniotic fluid index among low-risk pregnancies.

Abstract

To establish longitudinal reference intervals for pulsatility index (PI) and systolic velocity (SV) of the fetal renal artery, and to evaluate their correlation with the amniotic fluid index (AFI). A prospective longitudinal study was conducted among women with low-risk pregnancies who attended outpatient clinics at the University of Campinas Medical School, Brazil, at 16-19 weeks of pregnancy between April 1, 2008, and March 31, 2010. Doppler velocimetric measurements of the fetal renal artery and assessments of the AFI were undertaken at 4-week intervals to 36 weeks, and every 2 weeks thereafter until delivery. A total of 63 women were enrolled. The PI of the fetal renal artery showed little variation during pregnancy, whereas SV values increased to 36-37 weeks of pregnancy and decreased thereafter. No correlations were found between the AFI and the fetal renal artery Doppler velocimetric parameters (P>0.05 for all). The intraclass correlation coefficients for intra-observer and inter-observer variability indicated good reproducibility of SV, but the reproducibility of PI was lower. The AFI did not correlate with fetal renal artery Doppler velocimetric measures among low-risk pregnancies. However, investigations are needed among high-risk pregnancies.