ABSTRACT
Biochemical screening is applicable only to singleton pregnancies, so ultrasonic assessment is again mandatory. In 1956, the first biochemical marker identified in maternal serum was alpha-fetoprotein (AFP); the association between a raised serum AFP and open spina bifida was not demonstrated until 1974. AFP screening was intended for the detection of open spina bifida, and not closed spina bifida. AFP screening has a minor role in the detection of fetal defects due to the widespread use of sophisticated ultrasound techniques. The main area of development of other biochemical markers in pregnancy has been in screening for Down’s syndrome. A major challenge in the delivery of Down’s syndrome screening services is the need to set up an adequate organisational structure. Many more biochemical substances have been identified that are produced during pregnancy. Simultaneously using markers from both trimesters yields a better screening performance than using markers in either trimester alone.
