According to the data of the World Health Organization, chromosomal disorders are observed in 0.3% of all new-borns, in 25% of all miscarriages and in 50-60% of miscarriages which occur in the first trimester of pregnancy. Chromosomal diseases in a foetus increase with the woman’s age because as a woman ages, the percentage of abnormal eggs increases as indicated below: 30 years of age 1/385 chance 40 years of age 1/63 chance 45 years of age 1/19 chance