الفهرس 
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Abstract
The fetus receives its oxygen supply across the placenta, to which oxygen is delivered by maternal blood. The amount of oxygen delivered to the placental site is determined by the magnitude of blood flow and the oxygen content of uterine arterial blood. Transfer of oxygen from maternal to fetal blood is influenced by the diffusion gradient for oxygen between the maternal uterine blood and fetal umbilical blood. The diffusion gradient is affected by the thickness of the placental tissues separating the uterine and umbilical bloods and the relationship of arteriovenous flow patterns in the uterine and umbilical circulations.
Intrauterine hypoxia is a significant clinical challenge in obstetrics that affects both the pregnant mother and fetus. Intrauterine hypoxia can occur in pregnant women living at high altitude and/or with cardiovascular disease. In addition, placental hypoxia can be generated by altered placental development and spiral artery remodeling leading to placental insufficiency and dysfunction. Both conditions can impact normal maternal cardiovascular homeostasis leading to preeclampsia and/or impair transfer of O2/nutrient supply resulting in fetal growth restriction.
Under physiological conditions the fetal renal blood flow represents 2-3% of the cardiac output because of the very high resistance in the human fetal renal artery. During the third trimester of pregnancy, fetal renal arterial resistance decreases moderately, with increase in the End-Diastolic Velocity and mean velocity and only minor changes seen in the Peak Systolic Velocity possibly related to the increased blood flow of the renal circulation. During hypoxemia, the renal blood flow fell by 25–50% as compared to the baseline values, but the exact mechanism of this reduction has not been elucidated. A direct relationship has been reported between hypoxia and the renal artery pulsatility index.
Flow velocity waveforms from branches of the abdominal aorta including the renal arteries potentially provide a more sensitive method to predict the adequacy of fetal oxygenation than an examination of aortic flow, Investigation of multiple fetal vessels improves the validity of blood flow parameters.
Fetal renal arterial resistance index decreases moderately during the third trimester of pregnancy, possibly related to the increased blood flow of the renal circulation. In the fetus, the high vascular resistance observed in the lower extremities during the third trimester cannot explain the reduced renal vascular resistance of advancing gestation, since this increased lower extremity vascular resistance is associated with a decreased umbilical arterial vascular resistance.
The aim of the study was selected to be conducted to study fetal Renal Artery Doppler in normal and high-risk pregnancy. The validity of abnormal renal artery doppler in late weeks of pregnancy as a marker of fetal hypoxia was assessed in relation to umbilical artery and MCA doppler indices. The impact of abnormal doppler of fetal arteries on the renal and fetal circulation, amniotic fluid index, birth weight, and fetal condition at birth were evaluated in both complicated and uncomplicated pregnancies.
This was randomized prospective observational study was conducted at the Obstetrics and Gynecology Department, Benha University Hospital including 120 women attending the antenatal care clinic with pregnancy of more than 34 weeks of gestation referred after acquiring all the necessary formalities as pre‐ conception & prenatal tests as high-risk pregnancy or for routine ANC. The duration of the study had been from 6 to 12 months.
The main results of the study revealed that:
Cases more than 30 years were higher 59(49.2%). Age ranged from 23-36 with mean value 30.02±4.222. Normal cases were 32(26.7%), cases with hypertension were 49(40.8%), gestational DM cases were 27(22.5%), cases with oligohydramnios were 4(3.3%) and cases with Small for gestational age fetus were 4(3.3%).
Women’s complication in Uncomplicated group show that 9(27.3%) with no complication, 4(12.1%) had Oligohydramnios and 20(60.6%) had Small for gestational age fetus while in Complicated group 37(42.5%) with no complication, 34(39.1%) had high blood pressure and 16(18.4%) had Small for gestational age fetus. There was statistically significant differences between groups where P<0.001.
Women’s Renal Artery PI in Uncomplicated group was ranged between 1.60 – 2.05 with mean±S.D. 1.804±0.150 while in Complicated group was ranged between 1.60 – 2.05 with mean±S.D. 1.836±0.125. There was no statistically significant differences between groups where P=0.279.
Women’s Renal Artery Vmax in Uncomplicated group was ranged between 5.54 – 8.54 with mean±S.D. 7.046±0.888 while in Complicated group was ranged between 5.52 – 8.54 with mean±S.D. 7.100±0.901. There was no statistically significant differences between groups where P=0.770.
Women’s UMA PH in Uncomplicated group was ranged between 6.20-9.90 with mean±S.D. 7.885±1.239 while in Complicated group was ranged between 6-9.90 with mean±S.D. 7.905±1.182. There was no statistically significant differences between groups where P=0.885.
Women’s Fetal Outcome (Apgar score) in Uncomplicated group was ranged between 5-10 with mean±S.D. 7.61±1.802 while in Complicated group was ranged between 5-10 with mean±S.D. 7.49±1.718. There was no statistically significant differences between groups where P=0.745.
In conclusion, Reduction in the percentage of cardiac output directed towards the kidneys in cases of fetal hypoxemia leads to increased fetal renal artery pulsatility index with decreased renal perfusion. This decreased renal perfusion could be responsible for impaired nephrogensis and decreased kidney volume in fetuses with intrauterine growth restriction.
Based on our results, we recommend for further studies on large geographical scale and on larger sample size to emphasize our conclusion.