What are the different types of Down syndrome tests?
There are two basic types of Down syndrome tests: screening and diagnostic tests.
Down syndrome screening includes the following tests done during pregnancy:
First trimester screening includes a blood test that checks the levels of certain proteins in the mother's blood. If levels are not normal, it means there is a higher chance of the baby having Down syndrome. The screening also includes an ultrasound, an imaging test that looks at the unborn baby for signs of Down syndrome. The test is done between the 10th and 14th week of pregnancy.
Second trimester screening. These are blood tests that also look for certain substances in the mother's blood that may be a sign of Down syndrome. A triple screen test looks for three different substances. It is done between the 16th and 18th week of pregnancy. A quadruple screen test looks for four different substances and is done between the 15th and 20th week of pregnancy. Your provider may order one or both of these tests.
If your Down syndrome screening shows a higher chance of Down syndrome, you may want to take a diagnostic test to confirm or rule out a diagnosis.
Down syndrome diagnostic tests done during pregnancy include:
Amniocentesis, which takes a sample of amniotic fluid, the fluid that surrounds your unborn baby. It is usually done between the 15th and 20th week of pregnancy.
Chorionic villus sampling (CVS), which takes a sample from the placenta, the organ that nourishes your unborn baby in your uterus. It's usually done between the 10th and 13th week of pregnancy.
Percutaneous umbilical blood sampling (PUBS), which takes a blood sample from the umbilical cord. PUBS gives the most accurate diagnosis of Down syndrome during pregnancy, but it can't be done until late in pregnancy, between the 18th and 22nd week.
Down syndrome diagnosis after birth:
Your baby may get a blood test that looks at his or her chromosomes. This test will tell you for sure whether your baby has Down syndrome.
