Clinicians were able to identify aberrant fetus blood flow and assess perfusion of the fetus organs. The paper aims to compare the renal blood flow and cerebro-placental proportion in pregnant women whose pregnancy is complicated with isolated oligohydramnios versus women with a normal amount of liquor to study the effect of oligohydramnios on renal artery Doppler blood flow. This was a case-control investigation, conducted at Al-Menshawy General Hospital, Tanta and Al-Zahraa University Hospital of Al-Azhar University on 100 pregnant women recruited from (maternal age between 20 and 40 years with single viable intrauterine pregnancy and gestational age between 22 and 40 weeks). The patients were split into two groups, each with 50 patients. Group A (n=50): Pregnant women who were present with oligohydramnios, Group B (n=50): Pregnant women with normal Amniotic fluid index, during the period from April 2021 till December 2021. All patients were submitted to a medical history, a physical exam, Cardiac and chest examination, laboratory investigation (Complete blood picture and urine analysis, Urinary albumin, random blood sugar), Abdominal Physical examination, Abdominal ultrasonographic examinations and Doppler velocimetry of renal artery, umbilical, and middle cerebral artery. The Resistance Index and Pulsatility index of the renal artery are significantly higher in cases with isolated oligohydramnios compared to pregnant women with the normal amount of amniotic fluid, there is a significant negative correlation between the Amniotic Fluid Index and Resistance Index as well as the Pulsatility index (PI) of the renal artery, we conclude also that Pulsatility index of Renal Artery (PI-RA) can significantly detect Oligohydramnios at cutoff 1.52 with sensitivity, specificity, Positive predictive value (PPV) and Negative predictive value (NPV) of 100%, 100%, 100% and 100% (p<0.001) so it may be used as a predictor for the development of susceptible isolated oligohydramnios, we conclude also that the functional affection of kidney is the main cause of isolated oligohydramnios, and it occurs due to impairment of the physiological function of the kidney which detected by impairment in renal artery perfusion despite no organic affection.