One of the main questions in assisted reproductive techniques is how to prevent premature LH surge using a variety of protocols depending on either pituitary down-regulation, in GnRH agonist protocols, or by receptors blockage, in GnRH protocols. It is possible to say that GnRH protocols are most popular nowadays. The study aimed to assess the effectiveness of early antagonist administration during days ≤6 and later antagonist administration on days >6 on assisted reproductive outcomes. Women admitted to the ART Department at the High Institute for Infertility Diagnosis and ART, Al-Nahrain University, Baghdad, Iraq were included in the study. Reproductive outcomes were evaluated in early ≤6 and late >6 antagonist administration in a total of 44 normal responders, as follows. Sandwich protocols in 14 patients that received antagonists in the first 3 days of the follicular phase and conventional flexible antagonist protocol in 30 patients. We compared the outcomes between the two groups. There were no differences between early antagonist administration ≤6 and late >6 days in the number of MII oocytes, 2PN, the number of transferred embryos, grades of the embryos, and pregnancy rates. However, there were statistically significant differences between the duration of stimulation and the total Gonadotropin dose required. There was no effect of antagonist administration on days ≤6 and >6 on controlled ovarian stimulation on assisted reproductive outcomes.