Introduction: Controlled ovarian hyperstimulation (COH) is the initial stage of in vitrofertilization/intracytoplasmic sperm injection (IVF/ICSI) procedures. COH aims to produce multiple follicular development in order to harvest a suitable number of oocytes, which can later be fertilized. Methods: Women aged 20 to 40 years old who attended at the IVF unit (Kasr El- aini hospital - Faculty of Medicine - Cairo University) and private centers for IVF, the study included 72 infertile women who were candidate to receive the conventional antagonist protocol.They randomly divided into 2 groups:Group(A)(n=36):Estradiolvalerate(E2)isadministeredatdailydoseof4mgfrom day20oftheprecedingcycleonwardsformaximum10days.StimulationwithFSH should be started with the gap of 1 day after the last dose of E2. Group (B) (n=36): served as controls that remain untreated during the lutealphase.