الفهرس 
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Abstract
The current study was a prospective study carried out to clarify the hemodynamic changes in regional Doppler blood flow velocity in premature newborn infants that are associated with postnatal age and to examine the risk factors that might be associated with changes that influence cerebral hemodynamics. Throughout 18 months Forty-seven preterm infants were enrolled into the current study. Cerebral blood flow velocities in both the anterior and middle cerebral arteries were measured during the first 12 hours of life, 5th day, and 14th day of postnatal age. RESULTS: 1-The decline in resistance index with postnatal age reflects decrease in cerebrovascular resistance and subsequently increase in the cerebral blood flow in the first 5 days of life, which continue to increase till the 14th day of life. 2-An increase in the perfusion pressure with postnatal age is possibly due to transmitted changes in the systemic blood pressure through the compromised cerebral autoregulation mechanism in preterm infants over the first 5 days of life. 3-Chorioamnionitis is associated with lower cerebrovascular resistance and lower systemic blood pressure that may reflects a direct vasodilator effect of neurotoxic cytokine on the cerebral vascular bed. Moreover, the lower perfusion pressure among those babies will compromise the cerebral blood flow, and may lead to cerebral ischemia offering a concomitant or alternative hypothesis for development of cerebral damage in preterm infants. RECOMMENDATIONS 1-Extended follow up of the preterm infants is recommended in order to detect their neurodevelopmental outcome for evaluating the efficacy of the cerebral blood flow velocity measurement in predicting the neonatal morbidity. 2-Further studies of the risk factors such as inflammatory cytokine profile concomitant with cerebral blood flow velocity measurement in babies born to mothers who had chorioamnionitis who developed brain damage for better understanding of the exact mechanism of its development. 3-Extended follow up of the cerebral blood flow velocity measurement in preterm infants beyond 2 weeks of life for better evaluation of the postnatal age effects. 4-Larger studies looking for the effect of patent ductus arteriosus on cerebral blood flow velocity measurement in preterm infants. 5-Larger studies looking for the effect of different medications such as Dopamine, Morphine, and Indomethacin on cerebral blood flow velocity measurement in preterm infants.