Down Syndrome occurs if a baby has three copies of its 21st chromosome instead of two copies. A chromosome is a bundle of genetic material, and if you have too many or too few of these bundles, severe abnormalities can result. In the case of Down Syndrome, these include abnormalities of the intellect, heart, thyroid and other endocrine systems, facial appearance and others.
It is possible to detect early in the pregnancy whether your baby might be at high risk of having Down Syndrome. This is possible through consideration of your age and additional tests.
The additional tests are Combined First Trimester Screening and Non-invasive Prenatal Testing (NIPT).
It is important to realise that both of these tests are considered to be “screening tests”. This means they won’t tell you “yes, your baby has Down syndrome” or “no, it definitely does not have Down syndrome”. They will, however, say if your baby is at high risk of having Down syndrome, in which case you should have a diagnostic test. A diagnostic test is one that will tell you “yes” or “no”.
Combined First Trimester Screening requires a blood test at 10 weeks and an ultrasound between 12 and 13 weeks. Most patients choose this option. The blood test costs about $120 (no Medicare rebate) and a specialised ultrasound costs about $150 after the Medicare rebate; however, this varies from clinic to clinic.
NIPT is no doubt the future of prenatal testing for Down Syndrome and other genetic abnormalities, due to its incredible accuracy and lack of risk to the baby. It uses a maternal blood sample to find and test the baby’s cells in the mother’s bloodstream. Costs are constantly falling but it is quite expensive, costing about $550, and no rebate applies.
Most women would still opt for a 12 week ultrasound if doing NIPT; while the ultrasound has no impact on the Down Syndrome result when doing NIPT, it does provide other useful information about the development of the baby, so a saving is often not made by omitting the ultrasound.
Chris will discuss these options with you in detail at your first pregnancy appointment.