Abstract: Dimeric inhibin concentration can be used in the determination of the risk of a women carrying an unborn child affected by chromosomal abnormalities, e.g. Downs Syndrome. A method for antenatal screening for chromosomal abnormalities is carried out by measuring body fluid taken from a pregnant woman for the level of at least one marker or precursor or metabolite of the marker together with the gestational age of the woman are compared with reference values taken from women carrying fetuses with chromosomal abnormalities and/or women carrying normal fetuses, using dimeric inhibin as a marker. A second marker is the free beta subunit of human chorion gonadotropin. An apparatus for carrying out the method described comprises a computer with a means for comparing the values described.