Objectives: To determine 1) flow velocity waveform patterns in the fetal renal artery in normal pregnancies and pregnancies complicated by polyhydramnios or oligohydramnios, and 2) fetal urine output in twin gestations complicated by polyhydramnios-oligohydramnios syndrome.
Methods: Doppler waveforms were recorded in 121 normal fetuses, ten fetuses with oligohydramnios, ten with polyhydramnios, and eight sets of diamnionic twins with polyhydramnios in one gestational sac and oligohydramnios in the second sac. In the twins, the fetal urine output was also estimated.
Results: The pulsatility index (PI) of the renal artery in normal fetuses decreased linearly with advancing gestation. Abnormal renal artery PIs were found in four fetuses with oligohydramnios. The values in the singleton pregnancies complicated by polyhydramnios were in the range of normality for our reference limits for gestation. The PI of the renal artery in the twins with polyhydramnios was significantly lower than that from the twins with oligohydramnios. The urine output was significantly higher in twins with polyhydramnios than in twins with oligohydramnios.
Conclusions: Normal pregnancies are associated with changes in the renal artery flow velocity waveforms. In fetuses with oligohydramnios, the worst fetal outcome seems to be associated with abnormal renal artery flow velocity waveforms. In fetuses with polyhydramnios, no abnormal renal artery flow velocity waveforms were found. Changes in renal perfusion influence urine output in twin gestations complicated by polyhydramnios-oligohydramnios.