Testing for Down Syndrome and Birth Defects
Down syndrome is a condition marked by low IQ, peculiar facial features, and sometimes birth defects of the heart, spine and stomach. It is a genetic syndrome, but NOT INHERITED. Family history does Not matter. Down syndrome is the result of having an extra chromosome, also known as Trisomy 21. Tri is for three, 21 is for the 21st chromosome. Its cause is random, and related to the age of the mom.
There is specific testing for Down syndrome because all the other tests of pregnancy may not detect it. The pieces-parts-gender if you want to know ultrasound done in most pregnancies at 20 weeks does NOT reliably detect Down syndrome. The twenty week ultrasound CAN find birth defects of the heart, spine and other things that change how we do prenatal care and may impact delivery. Ultrasound findings are not diagnostic of Down syndrome, but a normal 20 week ultrasound decreases the chance of Down syndrome by Half.
There are tests designed to detect and diagnose Down syndrome. Each test is scheduled at a particular week of pregnancy, and all are done early, typically between 8 and 16 weeks. This testing is optional. We can do full prenatal care without the Down syndrome testing. Prenatal care, labor, delivery, and all pre-baby stuff is “the same” for babies with and without Down syndrome.
- Invasive tests which can cause miscarriage just by doing the test. These tests, Chorionic Villous Sampling (CVS) at 10 weeks and Amniocentesis (Amnio) at 14 weeks, give YES or NO results.
- Ultrasound measurement of the neck, done at 11-13 weeks. This identifies pregnancies with a higher chance of Down syndrome. If risk is identified then an amniocentesis is necessary to be certain.
- Blood test looking for fetal blood cells in the mother’s blood, done after 10 weeks. This is new and will probably replace all the other tests, soon. For now, its accurate, safe for mom and baby, and Expensive. Most insurance companies don’t cover this test, and it can cost over $250.
- Blood test done at 15 weeks include the Triple or Quad screen measures three or four substances in maternal blood. The test identifies pregnancies with a higher chance of Down syndrome. If risk is identified then an amniocentesis is necessary to be certain.
Years ago it was decided that 1/200 was the definition of higher chance of Down syndrome. Women age 35 yrs old at their due date have about a 1/200 chance of having a baby with Down syndrome. The neck ultrasound and triple/quad screen test results read: “one in some number.” If the “some number” is greater than 200 the test is considered Normal. If the number is less than 200, we have identified increased chance.
Some women/couples may consider pregnancy termination instead of carrying a baby with Down syndrome. Some women/couples want to “prepare” for a child who will be born with Down syndrome. Some just want to know that everything is OK. Each of these reasons is valid, and each has a catch….it’s not necessarily as easy as it sounds. The YES/NO tests for Down syndrome are the CVS and Amnio. These tests cause a miscarriage (from the test) about 1 in 200 times.
There is no simple response to this question. Consider this: medical tests are designed to help decide between two different paths, decisions, or interventions. The only “intervention” for Down syndrome is pregnancy termination. And the only certainty of diagnosis available, today, is an amnio or CVS test. If a woman/couple will not consider CVS, amnio or termination, there may be no reason to do this testing.
Ultrasounds in pregnancy are done for a variety of reasons, even though your favorite is getting a quick glimpse of the life growing inside of you. They are done at in a series of stages and are used to do everything from confirm the pregnancy, check for abnormalities, and can even tell you your baby’s gender…[read more]
Once you become pregnant there will be a series of tests conducted throughout the course of your pregnancy to insure that everything is progressing appropriately. Here is a brief overview of what you can expect…[read more]