Preterm birth is the costliest complication of pregnancy and the leading cause of neonatal morbidity and mortality. There are multiple strategies to minimize the risk and the impact of prematurity, such as administration of antenatal corticosteroids (ACS), in association with tocolysis, neuroprotection with magnesium sulphate, and neonatal life-saving therapies. The main objective of this paper is to compare between effect of administration of dexamethasone and betamethasone, used for lung maturity on daily fetal movement count and fetal doppler flow velocity waveforms of umbilical artery and middle cerebral artery. Patients and methods: This was a Double blinded prospective comparative trial, was carried out at the Department of Obstetrics & Gynecology at Al- Obour Hospital for health insurance in Kafr Elsheikh & at Bab AL-Sharia University Hospital, on 100 pregnant women with indication for corticosteroid according to American college of obstetrics and gynecologists (ACOG) pregnant women between 24 weeks and 33 weeks of gestation associated with fetal lung immaturity) divided into 2 groups from 1st of March 2021 till 31 August 2021. There is a significant change regarding fetal movements in Betamethasone group only. There is a significant increase regarding umbilical artery RI in both groups, the increase was higher in Dexamethasone but still in normal range. Conclusion is dexamethasone causes significant decrease in middle cerebral artery decrease after one week but still in normal range. There was a significant increase regarding umbilical artery RI but in Dexamethasone was higher however still in normal range. In our study There was a significant decrease regarding fetal movements in Betamethasone group only post treatment one day and one week.