N680S Polymorphism of the FSHR Gene and Its Relationship With the Type of Gonadotropin Used in COS

The investigators want to investigate whether the N680S polymorphism of the FSRH gene could affects ovarian response with different nature of the FSH used (human FSH and recombinant FSH) in patients undergoing two consecutive cycles of IVF/ICSI with controlled ovarian stimulation. All patients who agree to participate in the study will have a blood sample taken on the same day as a routine extraction performed for the 2nd cycle of the controlled ovarian stimulation in accordance with the standard clinical practice of each hospital. The sample will be sent to the central laboratory to determine the genotype of the afore mentioned polymorphism and correlate it with the clinical results obtained with the two cycles of controlled ovarian stimulation. In order to avoid any bias, the study population will follow a crossover design with respect to the type of FSH used in the first and second cycles of the COS (i.e., half of the recruited patients must have undergone a first cycle of COS with recombinant FSH and a second cycle with human FSH; and, conversely, the other half must have undergone a first cycle with human FSH and a second cycle with recombinant FSH). In order to avoid potential modifications to the inclusion criteria, the time elapsed between the two cycles should not exceed 6 months.