Background: Preeclampsia, is development of new onset hypertension with proteinuria and leads to endothelial disorder with multiple organ involvement in pregnant women. Severe pre-eclampsia is characterized by the progressive deterioration of both mothers and fetus. The use of MgSO 4 is beneficial in severe PE. Aim of Study:This study aimed to assess the effect of Magnesium sulfate injection on Doppler indices and fetal circulation in cases of severe pre-eclampsia. Patients and Methods:This was a prospective comparative study conducted on 50 pregnant female with severe preeclampsia, selected from the Obstetrics and Gynecology Department of Damanhour Teaching Hospital during the period from Jan 2019 to Dec 2020 and were classified into group (A) and (B) each included 25 women (A) treated by ordinary management with MgSO 4 (I.V) and (B) with ordinary treatment of preeclampsia only. Doppler is used to assess the UA for follow-up.Data were fed to the computer using IBM SPSS software package version 20.0.Results: Our results revealed a non-significant statistical difference between both groups regarding demographic data of women, investigations done except AST and ALT there was a significant elevation in group B; also, there was significant decrease in UAI, UARI and systolic diastolic ratio of UA.In our study there was no difference between both groups regarding post-therapy complication either fetal or maternal. Conclusion:We can conclude that MgSO 4 when used decreases the incidence of complications in severe PE as well as reduces the uterine artery indices with beneficial effect on fetus.