Down Syndrome Screening

Reviewed by James Brann, MD
Being pregnant, you probably wonder about a host of medical issues, one of which has to do with Down syndrome. The question many new mothers wonder is if they should undergo a screening test for Down syndrome while pregnant.
Before you answer that, first you need to understand what Down syndrome is. It is a condition a child is born with, that lasts a lifetime. Down syndrome may lead to medical problems with a person’s stomach, blood, heart or other organs. It may also lead to learning problems. Both the medical and learning problems may be either mild or they may be severe.

In the case of Down syndrome, a person has an extra chromosome. A chromosome is in your cell, and is the large structure that provides a home to thousands of your genes. Because of the extra chromosome, people with Down syndrome look a little bit different than people who do not have Down syndrome.

In reality, a woman can give birth to a child with Down syndrome at any age. The statistics are roughly one in every 700 babies. However, as a woman ages, the likelihood of having a child with Down syndrome increases. The likelihood also increases if the mother has a close family member with Down syndrome.

So how do you test for Down syndrome while a child is still in the womb? Screening tests aren’t able to tell you positively whether you child has Down syndrome before birth. However, if the screening test comes back showing there’s a high probability the child has Down syndrome, a mother can then undergo another test. Simply doing the screening test will not increase your chance of having a miscarriage, or rather your pregnancy ending on its own.
Women have the choice of whether to be screened. While some choose to go ahead with the screening, others do not. It is a personal choice. The types of screening depend on which stage you are in your pregnancy and what’s available where you live.
Overall, though, screening tests may involve:

  • Blood tests - In this test, a mother has blood drawn
  • Ultrasound - In this imaging test, a picture of the baby is created
  • Both ultrasound and blood test

Again, screening for Down syndrome is a personal choice, but a mother may want to do it to learn more about her child’s health, or if she’s concerned and wants to know how high the chances are that her baby may indeed have Down syndrome. She may either want to use this knowledge to learn more about it, choose a hospital with a certain level of expertise, or even choose to end her pregnancy.

On the other hand, many women choose not to do a screening test. In this case, sometimes a mother knows she will still carry her child to term no matter the results. She may also decide that she wouldn’t want to go ahead with the diagnostic test if the screening showed a high chance of Down syndrome. In other cases, the mother may simply want to know for sure, so she’ll skip the screening test and go straight to the diagnostic test.

Testing for Down syndrome

The next step usually if the screening comes back with a high probability of Down syndrome, has to do with the diagnostic tests. Only they can tell you for sure whether your child has Down syndrome. There are two types of tests. They include:
  • Amniocentesis - During this type of test, your doctor will insert a needle into your uterus and remove some of the fluid surrounding your baby. The test is primarily done between weeks 15-20 of pregnancy, but may be done later in your pregnancy.
  • Chorionic villus sampling, or “CVS” - During this type of test, your doctor inserts a needle into your uterus and removes a small piece of the placenta. That is the organ responsible for getting oxygen and nutrients to our baby and carrying off the waste. A CVS test is primarily done at around week 11 or 12, but may be performed up to week 14.
A mother should be informed, though, that diagnostic tests, such as these, may include side effects. Doing so may slightly increase your risk of having a miscarriage

If you do choose to have the screening test and the results show a high probability of Down syndrome, you can choose to not continue on with the diagnostic test. You’re able to wait until your child is born, if you want, before any additional tests. If you find yourself unable to make a decision, you can always talk to a genetic counselor. This type of expert will be able to give you additional information so that you can make a decision. You can also talk to your nurse or doctor about the downsides, and the benefits, of the testing.

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