This is a single centre retrospective study in repeated implantation failure patients: < 39 years old, at least 4 D3 good quality embryos or 2 good quality blastocysts transferred without implantation, absence of known causes of implantation failures (uterine malformation, thrombophilia, severe male factor, uncontrolled thyroid disfunction, autoimmune disease).

Patients scheduled for PGS underwent one or more stimulation cycles (oocyte or blastocyst banking) in order to maximize chances of embryo transfer. PGS cycles are analyzed globally. Aditionally, PGS cycles with a single stimulation cycle are analyzed in comparison to standard IVF cycles.

Inclusion criteria:

• women < 39 years
• repeated implantation failure: at least 4 day 3 good quality embryos or 2 good quality blastocysts transferred without implantation

Exclusion criteria:

• partner with severe male factor, or abnormal sperm Fluorescence in situ hybridization (FISH) analysis
• presence of uni or bilateral hydrosalpinx, uterine malformation, thrombophilia, uncontrolled thyroid disfunction or autoimmune disease

Repeated implantation failure patients: patients <39 years old that have received at least 4 day 3 good quality embryos or 2 good quality blastocists with no implantation.