There are several methods of antenatal screening for aneuploidy, Most
are aimed at the identification of women at increased risk of Down syn
drome, the most common abnormal karyotype conferring a significant ris
k of serious long-term morbidity, Traditional maternal-age-based scree
ning has largely been replaced by programmes based on biochemical mark
ers in maternal serum in the second trimester of pregnancy. However, i
n recent years there has been a considerable drive towards earlier scr
eening such that there are now a range of potential programmes based o
n various combinations of maternal age, serum markers and ultrasound f
indings. There is currently much debate as to which are the most effec
tive methods of screening for aneuploidy. (C) 1998 Rapid Science Ltd.