Trisomy of Chromosome 21 Diagnosis by High Output Sequencing

Inclusion Criteria: * Age ≥ 18 years, * patient coming from one of multidisciplinary prenatal diagnosis center * having à high risk of trisomy of chromosome 21 estimated by combine screening \> 1/250 * 11 weeks of gestation or high * accepting invasive prenatal diagnosis of chromosomal abnormalities * accepting genetic analysis of blood circulating DNA * Patient accepting to sign the enlightened assent Exclusion Criteria: * Patient of less than 18 years * combine risk \< 1/250 * refusing invasive prenatal diagnosis of chromosomal abnormalities * refusing genetic analysis of blood circulating DNA * Patient refusing to sign the enlightened assent