Introduction: 15 to 20% of clinical pregnancies end in spontaneous abortion and 25% of women will have an abortion during her life. Over 50% of cases of spontaneous abortions carry one or more chromosomal abnormalities. Objectives: To determine the frequency of chromosomal abnormalities in spontaneous abortions and its relationship with maternal age and other parameters like gestational age. Design: Transversal, descriptive study on secondary database. Setting: Cytogenetic Laboratory of the Instituto de Medicina Genética. Material: Samples of spontaneous abortions. Methods: Database analysis of 2319 samples of spontaneous abortions received between January 1996 and December 2013. Main outcome measures: Frequency of chromosomal abnormalities. Results: Of the 2 319 samples analyzed 1 595 showed abnormal karyotype (68.8%). Of all the numerical abnormalities (1 395/1 595) described, 83.2% c...