Merkatz (1984) showed that in 68% of live birth with Down Syndrome maternal age was 34 years or less. It would be desirable to define a high risk collective of women younger then 35 years with the help of a screening test, which could further on lead to a prenatal diagnostics. Several studies showed that low maternal serum alpha-fetoprotein levels (SAFP) in pregnancy is associated with fetal chromosomal abnormalities. The results of a retrospective study at the Department of Obstetrics and Gynecology at University of Mainz showed that maternal SAFP-level does not accomplish the demand of a prenatal screening test, because only 17% of the Down Syndrome could be diagnosed by this parameter. In case of trisomy 13 and 18 SAFP-concentrations were normal or even increased, maybe on account of the combination with other malformations like neural-tube or abdominal-wall defects.