Is there a test that the mother can take to find out if her baby will have Down syndrome?

There are several prenatal tests that can be performed to screen for the risk of Down syndrome in a pregnancy. These tests are typically offered to all pregnant women, but they are especially recommended for women who are at higher risk of having a baby with Down syndrome, such as older women and women who have a family history of the condition.

First-trimester screening

First-trimester screening is a combination of blood tests and ultrasound measurements that can be performed as early as 11 weeks of pregnancy. The blood tests measure the levels of certain hormones and proteins in the mother's blood that are associated with an increased risk of Down syndrome. The ultrasound measurement measures the thickness of the nuchal fold, which is a fold of skin at the back of the baby's neck. An increased nuchal fold thickness can be a sign of Down syndrome.

Second-trimester screening

Second-trimester screening is another combination of blood tests and ultrasound measurements that can be performed between 15 and 20 weeks of pregnancy. The blood tests measure the levels of different substances in the mother's blood that are associated with an increased risk of Down syndrome. The ultrasound measurement measures the length of the baby's thigh bone and the circumference of the baby's head. Shortened thigh bones and a small head circumference can be signs of Down syndrome.

Non-invasive prenatal testing (NIPT)

NIPT is a newer screening test that can be performed as early as 10 weeks of pregnancy. NIPT is a blood test that analyzes the DNA of the baby that is circulating in the mother's blood. NIPT can detect Down syndrome and other chromosomal abnormalities with a high degree of accuracy.

Diagnostic testing

If a screening test indicates that there is a high risk of Down syndrome, the mother may be offered diagnostic testing. Diagnostic testing can confirm whether or not the baby has Down syndrome. Diagnostic tests include chorionic villus sampling (CVS) and amniocentesis. CVS is a procedure in which a small sample of tissue is taken from the placenta. Amniocentesis is a procedure in which a small amount of amniotic fluid is withdrawn from the amniotic sac. Both CVS and amniocentesis can be performed before 20 weeks of pregnancy.

It is important to note that screening tests for Down syndrome are not 100% accurate. A negative screening test does not guarantee that the baby will not have Down syndrome, and a positive screening test does not necessarily mean that the baby will have Down syndrome. If a screening test indicates that there is a high risk of Down syndrome, the mother may want to consider diagnostic testing to confirm the diagnosis.