Progesterone (P) and estradiol (E2) are required for successful conception, both to prepare the endometrium for blastocyst implantation and pregnancy. During IVF cycles, the endometrium and embryo are exposed to supra-physiological concentrations of estradiol and progesterone during ovarian stimulation, which could influence pregnancy outcomes.This study analysed the relationship between serum progesterone/ estradiol concentrations on the day of HCG administration and IVF pregnancy rate in gonadotrophin-releasing hormone agonist protocols. The pregnant cases had a lower level of progesterone compared to non pregnant group with significant difference. On the other hand there is no statistically significant difference between both groups in relation to the estradiol concentrations on the day of HCG administration.