Down syndrome is a diagnosis that can be made during pregnancy. Down syndrome is a condition caused by the presence of an extra 21st chromosome. Chromosomes carry our DNA which is the material in the human body that makes the decision as to how we will grow, develop and how our bodies will work.
Most people have 46 chromosomes, or 26 pairs of chromosomes. People with Down syndrome have 47 chromosomes. They have 25 normal pairs. The 21st pair of chromosomes becomes three chromosomes rather than a pair so there's an extra 21st chromosome. Sometimes there's only part of an extra 21st chromosome present. If your baby is born with Down syndrome, which is also called Trisomy 21, he or she will have some physical and mental disabilities.
What Causes Your Doctor to Suspect That Your Baby May Have a Down Syndrome Diagnosis?
Most doctors suggest that expectant mothers have one of three tests that are called screening tests to see if their baby has Down syndrome. This is particularly true for mothers over 35, who are more likely to have babies with Down syndrome.
These three screenings include…
- ultrasound (imagining)
- maternal serum tests (blood tests)
- integrated screening which is a combination of both of these two tests
None of these tests can hurt your baby. They are simple, routine tests.
Your doctor will analyze these screening tests. Based on what your doctor can see on the ultrasound (or from chemicals detected in your blood) he may suspect that your baby has Down syndrome. If your doctor suspects Down syndrome then you most probably will be advised to go forward with diagnostic tests that can give you a much more accurate picture of whether your baby will have a Down syndrome diagnosis.
What Are Down Syndrome Diagnostic Tests?
Down syndrome diagnostic tests include:
- Amniocentesis – this is a test in which a thin needle is inserted in the mother's abdomen and then into her uterus. The baby is not harmed. It's usually performed at the 15th week or pregnancy or later. A small amount of fluid from the womb, called amniotic fluid, is removed and then tested.
- CVS (or chorionic villi sampling) – involves the removal of a bit of the placenta from the uterus. It's a test that's usually performed between the 10th and 12th week of pregnancy. Sometimes the doctor removes the piece of placenta with a catheter that is inserted into the mother's uterus through her vagina. Sometimes the piece of placenta is removed through a thin needle that's passed through the mother's abdomen into the placenta. For this test the doctor gives the mother a local anesthetic. The mother may spot a little after the test but will otherwise be fine.
- PUBS or Percutaneous umbilical blood sampling – this third test is usually only performed if there's an emergency of some sort and the doctor needs to know if the baby has Down syndrome right away. It involves taking a blood sample from the umbilical cord. A needle is inserted into the mother's abdomen and then into her uterus and into the umbilical cord. It's usually performed after the 18th week of pregnancy.
How Accurate Are Down Syndrome Diagnostic Tests?
Diagnostic tests are 98% – 99% accurate. This means, that if the diagnostic test comes back positive, your baby has a 98% – 99% chance of having Down syndrome.
What Are the Pros and Cons of Having Diagnostic Testing?
If your tests are positive, it means that it's time for you to learn as much as you can about Down syndrome and all that it will mean for you and your family. It's very difficult to learn that you will be giving birth to a child with a handicapping condition but children with Down syndrome can live long, happy and profitable lives. Knowledge of a Down syndrome diagnosis can help a family prepare for caring for the child once it's born, as well as preparing the physician for complications of the birth or with the newborn baby's health.
What are the Dangers of Diagnostic Testing?
There is, however, a downside to diagnostic testing. Diagnostic tests can cause miscarriage in a very small number of women.
- The rate of miscarriage is about 1-in-100 to 1-in-200 for women who have amniocentesis.
- The rate of miscarriage for women who have CVS (chorionic villi sampling) testing is slightly higher – 1 to 2 in 100 women.
- The rate of women who might have a miscarriage after PUBS (Percutaneous umbilical blood sampling) testing is slightly higher than for CVS testing.
You will have to decide whether or not you want to have Down syndrome diagnostic testing for your baby. There are pros and cons to diagnostic testing. And as parents, you will need to think about whether you need – or want – the testing. To a great extent this depends on the degree to which you need or want to know, before your baby's birth, if your newborn will have a Down syndrome diagnosis.
Science continues to develop more effective and safer tests. A new, relatively safe test is being tested but is not yet widely available for pregnant women. This test uses a small sample of the mother's blood and is able to identify the entire genetic code for a fetus. To read more about this test, read the article, New Test Can Predict Down Syndrome in Pregnant Women.
And to ensure your Down syndrome child stays healthy and happy, download my free guide "12 Tips for New Moms of Down Syndrome Babies" and sign up for my free newsletter. And to ensure your Down syndrome child thrives and you enjoy a wonderful loving relationship with your Down syndrome loved one, read my book, How to Live, Love and Succeed with Down Syndrome.