A healthy cell has 46 chromosomes which hold within them the complete genetic information. In rare cases a defect in this information exists. This can be a part of one chromosome relocating to another chromosome (translocation) or one chromosome missing completely.
Such defects can be diagnosed by taking a blood sample (karyogram). However, the changes in individual genes which transmit certain hereditary diseases to the child cannot be determined with this method. Dependant on the reason for infertility a higher risk of chrosomal anomaly (changes in the genetic information) can be detected in certain couples.