Tests For Down Syndrome
Down syndrome is a chromosomal defect resulting in a distinct appearance, some level of intellectual disability, and some developmental and health challenges.
Types of prenatal tests for Down syndrome are:
- Screening tests: These tests do not give you an exact answer, but let you know if your child is at an increased risk of Down syndrome. These screening tests do not harm the baby or mother.
- Diagnostics test: These tests are very accurate and give you an accurate answer. Diagnostic tests are usually recommended to women whose children are at an increased chance, as the screening tests show. A diagnostic test may increase the risk of a miscarriage, so they aren’t usually offered to all women.
You don’t need to undergo any screening or diagnostic tests if you don’t want to. Even If you have a screening test that indicates your child is at an increased risk of Down syndrome, you don’t have to go for the diagnostic test. You and your family should decide what is best for you, and you can also consult your doctor, genetic counselor, or midwife.
Screening for Down syndrome during pregnancy
The screening test for Down syndrome is offered as a usual part of prenatal care in the United States. If the age of a woman is over 35, and the baby’s father is over 40, or they have a family history of Down syndrome, you may need to get an evaluation.
First trimester
Blood tests and an ultrasound evaluation can look for Down syndrome in your child. These tests show a higher false-positive ratio than tests performed at later pregnancy stages. If test results aren’t normal, your physician may follow up with an amniocentesis after the 15th week of pregnancy.
Second trimester
A quadruple marker screen (QMS) test and an ultrasound can help diagnose Down syndrome and any other defect in the spinal cord or brain. This test is done during the 15 to 20th week of pregnancy.
If any of these tests are positive, you’ll be inspected at high risk for congenital disabilities.
Types of Screening tests
Following are the three types of screening test for Down syndrome:
Combined first-trimester screening
This test is done between 9 to 13 weeks (plus six days) of pregnancy to find out the chance of any kind of abnormality, including Down syndrome. This test is safe for both the baby and the mother. In combined screening, a computer is used to gather results from the following two tests:
A blood test is done between 9 and 12 weeks of the pregnancy, looking for any hormonal change that may suggest a problem with the fetus’s chromosomes.
An ultrasound scan is done between 12 to 13 weeks of the pregnancy. It measures the thickness of fluid present behind the baby’s neck, known as nuchal translucency. This is often enlarged in babies with Down syndrome.
These results, along with the mother’s age, show the risk of Down syndrome.
Non-invasive prenatal testing
The non-invasive prenatal test is a newer and sensitive form of screening to diagnose Down syndrome. In this technique, a simple blood test is done to analyze the DNA of the baby he passed into his mother’s bloodstream. This test is performed after ten weeks and is 99% accurate for Down syndrome.
NIPT tests are not covered by Medicare and are only done in private clinics. This test is more suitable for mothers who are at increased risk of having a child with Down syndrome.
Second-trimester maternal serum screening
Second-trimester screening, also called a ‘triple test’ or maternal serum screen (MSS), is done between 13 and 18 weeks of pregnancy. It is usually offered to mothers who missed their combined first-trimester screening test, or if it is not available where they live.
It includes a blood test to test the hormones that could indicate the child has neural tube defect or Down syndrome.
In addition to this test, most of the pregnant women undergo a morphology scan (or anomaly scan) at 18 to 21 weeks into the pregnancy to find out the baby’s growth and to check if the pregnancy is progressing well. This can sometimes diagnose Down syndrome.
Tests at birth
At birth, your physician will:
- Take a physical examination of your baby
- Perform a blood test (called a karyotype) to confirm Down syndrome.
Diagnostic tests
The only way of making sure whether your child has Down syndrome is to undergo a diagnostic test. Diagnostic tests can increase your risk of a miscarriage, so they are generally only offered to mothers who’ve had previous children with genetic abnormalities, who are at increased risk, and who have a family history of a genetic disorder.
Three tests can confirm Down syndrome:
Your doctor may prescribe additional tests to check for Down syndrome in your baby. These tests may include:
- Amniocentesis – A doctor will take a sample of amniotic fluid to find out the number of chromosomes your baby has. The test is usually performed after 15 weeks of pregnancy.
- Chorionic villus sampling (CVS) – A doctor will take a few cells from your placenta to examine fetal chromosomes. CVS is done between the 10th and 14th week of pregnancy. It may increase the risk of a miscarriage, but according to research, only by less than 1 percent.
- Percutaneous umbilical blood sampling (cordocentesis) – Your doctor will take a blood sample from the umbilical cord and will check for any chromosomal defects. This test is done after the 18th week of pregnancy. There is a high risk of miscarriage while performing this test, so it’s preferred only if other tests are uncertain.
Most women choose not to get these tests because of the higher risk of miscarriage. They rather prefer having a child with Down syndrome than to lose the pregnancy.
You will receive the test results after some days of the test. Your physician will explain the results, and he may offer you genetic counseling.
What to do with your results
It’s very difficult to accept that something is wrong with your child, especially if you’ve to face a painful decision about the future consequences of your pregnancy.
Your doctor or midwife will make sure you visit the appropriate medical professionals, such as a genetic counselor, to assist you to get all the knowledge and support you need to make the right decision for you and your child.
If the result of tests is positive, you may choose to keep the baby, end the pregnancy, or place the baby for adoption.
Consider how you would take care of a baby with Down syndrome and how this condition would affect your family. Thankfully, the viewpoints for people with Down syndrome are usually very good.