There are three screening tests for detecting Down syndrome:

1. Combined first-trimester screening
2. Non-invasive prenatal testing (NIPT)
3. Second-trimester maternal serum screening

In this blog, you will get to know about some basics of screening tests as mentioned below:

• Combined first-trimester screening

This screening test is done between 9 weeks and 13 weeks into the pregnancy to know the chances of Down syndrome. The main thing is that it is safe for both mother and baby.

A computer combines the results of two tests: a blood test and an ultrasound scan.

1. A blood test is preferred between 9 and 12 weeks to check hormonal changes that suggest there is a problem with the baby’s chromosomes.
2. An ultrasound scan is done at 12 to 13 weeks to measure the thickness of fluid behind the baby’s neck. The fluid’s thickness is mostly found larger in babies with Down syndrome.

• Non-invasive prenatal testing

This test involves a simple blood test that analyses DNA from the fetus that has passed into the mother’s bloodstream. The test is preferred after 10 weeks; more than 99% accurate for Down syndrome. Remember that, this type of test is most suitable for women who have more chances of having a baby with Down syndrome.

• Second-trimester maternal serum screening

The Maternal serum screen (MSS) is preferred between 14 and 18 weeks into the pregnancy. This screening test is also known as the triple test and is recommended to those women who missed the combined first-trimester screening test.

See more: Role of Short Tandem Repeat (STR) in the paternity test

It involves a blood test to check hormones that indicates the baby has Down syndrome. In case, if your baby has an increased chance of having Down syndrome, you will be offered a diagnostic test.