|What tests are there for Down’s syndrome?|
There are screening tests that can assess your chance of having a baby with Down’s syndrome. These are:
- Blood test plus nuchal translucency ultrasound scan
- Quadruple blood test
There are also diagnostic tests that will give you a definite diagnosis of Down’s syndrome and sometimes, other abnormalities. These are:
- Chorionic villus sampling (CVS)
|Screening tests during pregnancy|
Screening for Down syndrome is offered as a routine part of prenatal care. Although screening tests aren’t perfect, they can help you make decisions about more-specific diagnostic tests and the course of the pregnancy.
Various screening tests can help identify whether you have a high risk of carrying a baby with Down syndrome, but they can’t identify whether your baby has Down syndrome. Screening tests include the first trimester combined test, the integrated screening test and the cell-free fetal DNA analysis.
|The first trimester combined test|
The first trimester combined test, which is done in two steps, includes:
- Blood test
- This blood test measures the levels of pregnancy-associated plasma protein-A (PAPP-A) and the pregnancy hormone known as human chorionic gonadotropin (HCG). Abnormal levels of PAPP-A and HCG may indicate a problem with the baby.
- Ultrasound is used to measure a specific area on the back of your baby’s neck. This is known as a nuchal translucency screening test. When abnormalities are present, more fluid than usual tends to collect in this neck tissue.
|Integrated screening test|
The integrated screening test is done in two parts during the first and second trimester of pregnancy. The results are combined to estimate the risk that your baby has Down syndrome. This test can achieve the same level of detection as the first trimester combined test but with a lower false-positive rate, meaning that fewer women are incorrectly identified as carrying a baby with Down syndrome.
- First trimester
- Part one includes a blood test to measure PAPP-A and an ultrasound to measure nuchal translucency.
- Second trimester
- The quad screen measures your blood level of four pregnancy-associated substances: alpha fetoprotein, estriol, HCG and inhibin A.