When Can Ultrasound Detect Down Syndrome in Pregnancy?

Screening For Down Syndrome: World Down Syndrome Day is celebrated every year on 21st March. Down syndrome is a type of genetic disorder that affects children. The main reason behind this is a disturbance in the chromosomes. Usually, the number of chromosomes in a normal child is 46. Of these, 23 are sets of chromosomes from the mother and 23 from the father.

A child suffering from Down syndrome has an extra copy of chromosome 21. That is, the number of chromosomes in children affected by Down syndrome is 47. Compared to normal children, the mental and physical development of children suffering from Down syndrome is slow. Apart from this, children suffering from Down syndrome are also at risk of having heart problems.

In such a situation, often this question arises in the minds of many people Can Down syndrome be detected before the birth of the child? Yes, Down syndrome can be detected through some tests during pregnancy. Doctors usually use blood tests (such as NIPT) and ultrasound to detect Down syndrome during pregnancy. Some of these tests are up to 90 percent accurate in identifying the risk of Down syndrome in the fetus. Let's know what tests are done during pregnancy to detect Down syndrome.

Screening tests:

First trimester (10-14 weeks): Nuchal translucency (NT) ultrasound is done in the 11th week of pregnancy, in which the fluid behind the baby's neck is measured. This shows whether the child has Down syndrome or not. The dual marker test is done in the 13th week, in which the levels of β-hCG and PAPP-A are measured in the pregnant woman's blood.

Second trimester (15-20 weeks): AFP, hCG, estriol, and inhibin-A levels are checked to estimate the risk of chromosomal abnormalities.

Non-invasive prenatal testing (NIPT): This is a blood screening test that analyzes the fetal DNA present inside the blood of a pregnant woman. This test can help determine if the foetus is at risk of developing chromosomal disorders such as Down syndrome (trisomy 21), trisomy 18 (Edwards syndrome), and trisomy 13 (Patau syndrome).

Diagnostic tests:

If the screening test finds a moderate or high risk, these tests provide a definitive diagnosis.

Chorionic villus sampling (CVS): This is done at 10-13 weeks, in which a small sample of placental tissue is taken to check the fetus’ chromosomes.

Amniocentesis (15-20 weeks): This test is done to detect chromosomal abnormalities by examining the amniotic fluid.