Abnormal embryonic karyotype is the most frequent cause of recurrent miscarriage.

BACKGROUND We previously found that a normal karyotype in a previous miscarriage is a predictor of subsequent miscarriage. However, the prevalence of recurrent miscarriage caused by an abnormal embryonic karyotype has not yet been reported, since embryonic karyotype is not typically analyzed during conventional examinations. METHODS A total of 482 patients who underwent both embryonic karyotype determination and conventional examinations for recurrent miscarriage were enrolled in this study. The distribution of the causes and the live birth rate for each cause were examined. RESULTS The total percentage of subjects in whom conventional causes of recurrent miscarriage could be detected was 29.5%. The prevalence of the abnormal embryonic karyotype was 41.1% in the subjects in whom no conventional causes of miscarriage could be identified. The prevalence of recurrent miscarriage of truly unexplained cause, that is, of subjects without conventional causes in whom the embryonic karyotype was ascertained to be normal, was 24.5%. Among the patients in whom the first determination revealed an abnormal embryonic karyotype, 76.2% (32/42) showed an abnormal embryonic karyotype in the repeat determination as well. The cumulative live birth rate (71.9%) in women with recurrent miscarriages caused by the abnormal embryonic karyotype was significantly higher than that (44.7%) in women with recurrent miscarriages associated with the embryonal euploidy. CONCLUSION An abnormal embryonic karyotype was found to represent the commonest cause of recurrent miscarriage, and the percentage of cases with recurrent miscarriage of truly unexplained cause was limited to 24.5%.The two groups should be distinguished for both clinical and research purposes.