Antenatal screening for Down syndrome.

Antenatal screening for Down syndrome was introduced a quarter of a century ago. The risk of fetal loss due to amniocentesis and the costs of the procedure restrict antenatal diagnosis to women who are at high risk of having an affected pregnancy. Initially the only method of screening women to identify older women for the diagnostic test. In 1988, the introduction of antenatal serum screening using various biochemical markers together with maternal age improved the performance of screening considerably - the proportion of affected pregnancies identified in the 5% of women of highest risk increased from about 30% to over 60%. Current research is continuing to refine the screening methods to improve screening performance by the addition of new markers, by the combination of serum and ultrasound markers, and by carrying out screening earlier in pregnancy. Improvements in the technical quality of screening needs to be matched by continuing attention to the quality of the screening service and ensuring that the public are satisfied with the service.