Screening (alpha feto protein, maternal)

Measurement of maternal AFP levels is a useful tool in the prenatal diagnosis of many fetal disorders, including Down's syndrome, spina bifida, anencephaly and others.

Broadly the findings in AFP levels can be grouped into:

• High AFP
• Low AFP

The maternal blood is taken at 16 weeks gestation - an accurate estimation of gestational age is needed in order to allow the proper significance of a result to be assessed. The outcome of the test is to prompt further investigations if positive - i.e. it is not diagnostic.

• in the UK, maternal AFP is assessed in the context of other markers e .g. the quadruple test (hCG, AFP, uE3, inhibin A) to give a more accurate predictor of risk. However as many Trusts in England move to the offer of combined screening for Down's syndrome, AFP will no longer be measured and the screening test of choice for spina bifida and anencephaly will be the mid pregnancy ultrasound scan