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To Test or Not to Test?

Posted Oct 14 2008 5:00am
If you are pregnant, you will be encouraged to undergo prenatal testing. Up until recently only women 35 and over were offered testing. Now, both the American College of Obstetricians and Gynecologists and the Society of Obstetricians and Gynaecologists of Canada recommend all pregnant women regardless of age undergo testing. It is important that you know, you are not obligated to undergo testing - the decision is yours, not your doctor's. Before making a decision, you deserve to know exactly what is involved with testing - what are they looking for, what are the risks involved and how accurate are these tests?

Below you will find a chart taken from the Mayo Clinic website, outlining all the screening and tests available to you.

What it is

How it's done

What the results
may tell you


First trimester screen

Between the 11th and 14th weeks of pregnancy.

A two-step screening. First, a maternal blood test for two normal first-
trimester proteins. Second, nucal translucency ultrasound to measure a region under the skin behind the baby's neck.

A blood sample is taken from the mother's arm. Ultrasound takes fetal measurements.

Whether the baby has an increased risk of Down syndrome. May help detect certain heart defects or skeletal problems.

Because false positive results are possible, other tests — such as amnio. or chorionic villus sampling may be needed to confirm or rule out a diagnosis.

Quad marker screen

Between the 15th and 20th weeks of pregnancy.

Offered to women who did not complete first-
trimester screening.

Maternal blood test for four substances that normally come from a baby's blood, brain, spinal fluid and amniotic fluid.

A blood sample is taken from the mother's arm.

Whether the baby has an increased risk of certain developmental or chromosomal disorders, such as spina bifida or Down syndrome.

One in 20 women have false positive results, so a repeat quad marker screen, an ultrasound or other diagnostic tests may be needed.



Between the 18th and 20th weeks of pregnancy

Sound waves are used to create an image of the baby and the surrounding structures.

Sound waves from a transducer moved over the mother's abdomen are converted into images on a monitor.

Whether the baby's growth and development are on target. Can identify various congenital abnor-

Advanced ultrasound and other tests may
be needed. Some abnor-
malities can be treated prenatally.

If the results of a screening test are positive or worrisome, your health care provider may recommend a more invasive diagnostic test. Here are the basics on the most common prenatal diagnostic tests.

What it is

How it's done

What the results may tell you

Possible safety concerns



After the 15th week of pregnancy

A sample of the amniotic fluid is checked for specific genetic problems.

A sample of amniotic fluid is withdrawn from the mother's abdomen with an ultrasound
-guided needle.

Can identify chromosomal abnormalities and certain genetic problems, such as Down syndrome and spina bifida.

One in 200 risk of miscarriage when done before the 24th week of pregnancy.

Chorionic villus sampling (CVS)

Between the 9th and 14th weeks of pregnancy

A sample of the placenta is tested for genetic abnormalities.

Guided by ultrasound, a needle is inserted in the uterus or a thin tube is threaded through the cervix and a sample of placental tissue is removed.

Can identify chromosomal abnormalities and some specific genetic problems earlier than amniocentesis.

One in 100 risk of miscarriage.


taneous umbilical blood sampling (PUBS)

After the 18th week of pregnancy

A sample of the baby's blood is tested for genetic problems or infections.

A blood sample is taken from the vein in the umbilical cord through a needle inserted in the mother's abdomen. Ultrasound helps locate the vein.

Can identify sickle cell anemia, hemophilia, anemia, Rh disease and various other conditions.

Two in 100 risk of miscarriage.

Click here to find out more information on prenatal testing from the Mayo Clinic.

As you can see from the chart many of the screening procedures can produce false positives. Also, many of the diagnostic tests produce a risk of miscarriage. Not mentioned in the chart is that many of the diagnostic tests are not 100% accurate. According to WebMD"The accuracy of amniocentesis is about 99.4%. Amniocentesis may occasionally be unsuccessful due to technical problems such as being unable to collect an adequate amount of amniotic fluid or failure of the collected cells to grow when cultured."

There are some important things that you and your partner should consider and discuss before agreeing to any testing: will you pursue more invasive testing if the screening produces a high probability of Down syndrome, is it worth risking a miscarriage, would you terminate if the tests came back positive? According to Dr. Brian Skotko, a resident physician at Children’s Hospital Boston and Boston Medical Center, "reproductive couples need to discuss two main issues prior to undergoing prenatal testing including: when do you think life begins; and what form of human life does one believe is valuable".

In addition to this, it would be a great idea to find out what life with a baby with Down syndrome looks like today. Sometimes we are afraid of things we don't know much about. You may be surprised to hear what a fulfilling, joyful adventure raising a child with Down syndrome can be. Contact a Down syndrome society near you, talk to some parents who have children with Down syndrome. There are an endless amount of resources out there to educate you on Down syndrome. Check out the different links, articles, etc. on this blog. I am sure by doing all of this you will come away with a very positive outlook on Down syndrome. Be sure to watch the video clip on this blog of a baby with Trisomy 18, it is a beautiful story.
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