Testing for fetal abnormality in routine antenatal care.

The detection of fetal abnormality is a major component of routine antenatal care. A variety of techniques are now in use, although these are constantly being modified in the pursuit of more accurate and earlier detection. In this paper we draw attention to the distinction between screening and diagnostic tests, and describe the techniques which have been most commonly used in the UK: serum-screening for neural tube defects; screening for Down's syndrome; ultrasound scanning; amniocentesis and chorionic villus sampling.