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 pe
