Antenatal Screening and Diagnostic Tests

Around 1% of all babies are born with some kind of abnormality. Fortunately, most of these are minor, but a small percentage can be serious. Antenatal screening and diagnostic tests are available in New Zealand to try and predict and diagnose the possibility of these chromosomal and structural abnormalities. These tests can give you the option of termination of the pregnancy if a serious problem is found or in advance knowledge to help dealing with the problem before the baby is born.

Often parents are sure that they would not request termination of the pregnancy regardless of any abnormality found. It is important to remember that these tests are  optional, but sometimes factors such as age may mean that the tests are more likely to pick up problems. Your lead maternity carer should discuss the availability of these tests with you so that you have the option of an informed decision whether you wish to have them or not.
The screening tests vary in terms of reliability at picking up the problem and can also say there is a high risk of the problem falsely, i.e. when no problem exists. When considering whether to have the screening tests, it is worth remembering that if they come back 'high risk' (usually greater than 1 in 300), you will be offered a more accurate diagnostic test. The diagnostic tests are much more reliable but involve a small but significant risk of miscarriage. For many women, the decision to have these tests is a difficult one: your lead maternity carer should help you with the information needed to enable you to make this decision.

Down Syndrome

This is a set of mental and physical symptoms that result from having some extra genetic material (chromosome 21). Even though people with Down syndrome may have some physical and mental features in common, symptoms of Down syndrome can range from mild to life-threateningly severe. Mental and physical development are slower in people with Down syndrome. The chance of having a baby with Down syndrome increases as a woman gets older. Down syndrome cannot be cured, but many people with Down syndrome live productive lives well into adulthood.

Living with Down Syndrome - One family's story

Antenatal screening tests currently offered in New Zealand include the Nuchal Traslucency Ultrasound Scan, Maternal Serum Screening and the Anatomy Ultrasound Scan.

Antenatal Diagnostic tests currently offered in New Zealand include Amniocentesis and Chorionic Villus Sampling (CVS).

This section on antenatal screening and diagnostic tests has been prepared by Dr Anil Sharma,  an obstetrician and gynaecologist in  Auckland. www.dranilsharma.co.nz .