Fetal renal artery velocity waveforms and amniotic fluid volume in growth-retarded and post-term fetuses.

Renal blood flow velocity waveforms were recorded by Doppler ultrasonography in 114 growth-retarded fetuses and in 97 post-term fetuses. The pulsatility index (PI) values were compared with our reference limits for gestational age and related to the amount of amniotic fluid. Growth-retarded fetuses showed significantly increased PI values compared with normally grown fetuses, and this difference was particularly evident in cases of oligohydramnios. Furthermore, there was a significant negative correlation between the increase in PI and the amniotic fluid volume. Post-term fetuses showed no significant differences in PI values compared with term fetuses and no significant correlation between the amount of amniotic fluid and PI values.