Considering the number of retrieved oocytes, it has been recently purposed a new patient stratification during ART treatments: poor response (1-3 oocytes); sub-optimal response (4-9 oocytes); normal response (10-15 oocytes); high response (>15 oocytes). The reason to create this new category of sub-optimal responder is that they have poorer outcomes during ART treatments when compared to patients that have 10-15 oocytes retrieved. This category of sub-optimal responder has led to the introduction of new concept in reproductive medicine with the objective to stratify low prognosis patients undergoing ART based on the combination of quantitative and qualitative parameters. There is a group of patients that although present normal biomarkers of ovarian reserve, such as AFC and AMH, they have a sub-optimal response to COS. They have 9 retrieved oocytes, showing the inadequacy of using only the traditional ovarian reserve biomarkers to predict the ovarian response. This sub-optimal response should be related to ovarian sensitivity to exogenous gonadotrophins modulated by genetic factors.