Aim Intermittent assessment of renal artery flow velocity waveforms during the early stages of pregnancy may help in predicting changes in amniotic fluid dynamics. The current study sought to determine the relation of renal artery and umbilical artery flow velocity waveforms with normal pregnancies and pregnancies complicated by either polyhydramnios or oligohydramnios. Material and Methods Renal and umbilical artery Doppler values were evaluated at 22, 28 and 34 weeks' gestation in 300 low-risk pregnant women with singleton pregnancies. Pulsatility index (PI) and resistance index (RI) were recorded and the amniotic fluid volume was evaluated. Three groups were formed according to the amniotic fluid volume at birth. Group I consisted of 264 pregnant women with normal amniotic fluid, group II included 30 pregnant women with oligohydramnios and group III included six pregnant women with polyhydramnios. Doppler parameters were compared between the groups and within each group according to gestational age. Results Renal artery PI values were higher in group II than group I at 22 weeks, 28 weeks and 34 weeks. The PI value at 28 weeks' gestation was statistically significant (P=0.011). At 28 weeks' gestation, group II also had higher umbilical artery PI and RI values than group I. Conclusion An increase in renal artery PI develops in early pregnancy before the development of oligohydramnios. In pregnancies developing polyhydramnios, renal artery PI was lower; however, our study included a small number of women with polyhydramnios.