Down syndrome (also called Trisomy 21) is a genetic condition that can happen by chance, and affects around 1 in 700 pregnancies. Read more about Down syndrome. There are two much rarer genetic conditions (Edwards and Patau syndromes) that are also screened for in these tests. Since they are rarer, the tests are often known simply as Down syndrome tests.
Babies affected by one of these genetic conditions have an increased risk of miscarriage, stillbirth, death as a baby, or a wide range of long-term physical and mental disabilities.
Image credit: canva
Screening tests
MSS1 (maternal serum screening first trimester) or ‘combined screening test’
This is performed between 11 and 14 weeks, and involves having a free blood test and an ultrasound ‘nuchal translucency (NT)’ scan which you may have to pay for. This is the commonest test currently performed in Aotearoa New Zealand.
MSS2 (maternal serum screening second trimester)
This is performed between 14 and 20 weeks, and involves a single free blood test. This is the least accurate test, and is usually only suggested if you book in for pregnancy care after 14 weeks of pregnancy. You are also recommended to have an ultrasound scan (which you may be asked to pay for) to confirm pregnancy dates, count the number of babies and check for any early major problems, although this is not part of the MSS2.
NIPT (Non-invasive prenatal testing)
This is a newer test, which is commonly used in many other countries. It involves a single blood test, which can be taken any time from 10 weeks onwards and looks for genetic material from your baby in your bloodstream. It is much more accurate than the other 2 tests, but more expensive for you. Read more about non-invasive prenatal testing (NIPT).
An ultrasound scan is also recommended around 12 weeks to make sense of the results.
