Maternal serum screening test
The maternal serum screening test, a blood test that may indicate a higher-than-expected risk of certain birth defects, is performed on many pregnant women.
One of the most natural fears of those expecting a baby is that it will not be normal. Of course, the word ‘normal’ is hard to define, because we are all a little bit different.
Even so, most people are surprised to learn that about one baby in 20 has a birth defect, that is, an abnormality that is present at birth. This term covers a wide variety of conditions ranging from the relatively minor and easily fixed, such as dislocation of the hip, to very serious conditions where the infant may not survive.
Some of these problems can be detected during pregnancy, some are found at birth and others may only be discovered as the baby grows.
How does the maternal serum screening test work?
The maternal serum screening test is done when the pregnancy is at the 15-to-18-week stage. The test shows if there is an increased risk of Down syndrome or an open neural tube defect.
Down syndrome is an abnormality of the chromosomes resulting in children who often have multiple birth defects and some degree of intellectual impairment. The condition happens in fewer than one in 870 births. It is more common with older mothers, but can occur at any maternal age.
Open neural tube defect means there is a failure in the normal formation of the brain or spinal cord. This may result in a number of conditions including spina bifida and hydrocephalus (sometimes called water on the brain). About one in 2000 births will have a neural tube defect.
The maternal serum screening test does not identify the presence of these conditions but it indicates if there is an increased likelihood of them. Further tests can then be done to make the picture clearer.
The decision to have such tests is a very personal one and there are no hard and fast rules about who should or should not be tested. It is for each individual set of parents to decide. If you are pregnant, or contemplating having a baby, ask about screening tests, including the maternal serum screening test.
Last Reviewed: 09 December 2009
- 1. Royal Australian and New Zealand College of Obstetricians and Gynaecologists [website]. College statement: Prenatal screening tests for trisomy 21 (down syndrome), trisomy 18 (Edwards syndrome) and neural tube defects (published 2007, July). Available at: http://www.ranzcog.edu.au/publications/statements/C-obs4.pdf (accessed 2009, Dec 14)
