This study evaluates the effect of single embryo transfer (SET) with and without array CGH for the evaluation of the complete chromosome complement of the blastocyst. Patients will be allocated at random into two groups. The control group will consist of patients in which one embryo will be replaced on day 5 based on morphological and developmental characteristics, and the other embryos reaching blastocyst stage will be vitrified. The test group will consist of patients undergoing embryo biopsy at the blastocyst stage (day 5 of development, embryo freezing, and analysis of the biopsied cells with a comprehensive chromosome analysis technique (array Comparative Genome hybridization or aCGH). Only a chromosomally normal blastocyst will be replaced in a thawed cycle. Inclusion and exclusion criteria are described in the study population section.