To determine in our setting the cut-off value of Progesterone (P) serum levels on the day of human chorionic gonadotropin (hCG) administration that are predictive of a subsequent decrease of the clinical pregnancy rate. Prospective cohort study. Fifty four patients up to 39 years old that performed cycles of IVF/intracytoplasmic sperm injection (ICSI) with fresh embryo transfer between October 2014 and December 2015 were included in the study. All patients used a GnRH antagonist flexible protocol, presented with basal FSH < 20 mUI/ml, had obtained 2 or more MII oocytes in the retrieval and had at least one good quality embryo transferred. The level of P on the day of hCG was measured by electrochemiluminescence immunoassay with the reagent Progesterone II in the Cobas e-411 analyzer (Roche). Pearson's r coefficient was used to evaluate the correlation between P values and ovarian response variables. ROC curve analysis was used to determine cut-off values of P serum levels for predicting pregnancy rate. Pregnancy rates and patient characteristics were compared between groups. Chi-square test for trend was used for comparing clinical pregnancy rates between groups. Statistical analysis was performed using Medcalc 10.2.0.0, a p value of <0.05 was considered statistically significant. Two cut-off values of serum P levels were found, 0.7 and 1.46 ng/ml, dividing the population in three groups: Low P levels: ≤ 0,7 ng/ml (n= 14), Intermediate P levels : 0.7 to 1.46 ng/ml (n=25) and High P levels: >1.46 ng/ml (n=15). There was a significant difference in clinical pregnancy rates between patients from the groups of low, intermediate and high P serum levels (71,4%, 48,0% y 26,7%, p=0.016 X2 test for trend). P serum levels did not correlate with estrogen levels (r=0.22, p=0.10, 95% CI -0,05 to 0,46), number of follicles (r=0.20, p=0.13, 95% CI -0,06 to 0,45) or oocytes retrieved (r=0.26, p=0.053, 95% CI -0,003 to 0,50). Our results support previous studies showing negative IVF/ICSI outcomes with P elevation on day of hCG administration. In our setting this effect starts at a lower threshold than the commonly reported threshold of 1.5 ng/mL. These findings make argument for cryopreservation of embryos as elevated progesterone levels appear to negatively impact in clinical pregnancy rates.