Diagnostic tests
Screening tests can tell you your chance of having a baby with Down syndrome, trisomy 18 and open neural tube defects.
Diagnostic tests can tell for sure if your baby has one of these conditions. These diagnostic tests are available only if your screening test result is positive or if you are 35 years of age (in some areas, this has changed to 40 years of age) or older at your due date and in certain other situations.
Chorionic Villus Sampling (CVS)
CVS is a test which tells for sure if your baby has Down syndrome or trisomy 18. This test is usually done between 11 and 13 weeks of pregnancy. Using ultrasound, a small piece of tissue is removed from the placenta for testing, usually through the vagina, but sometimes through the abdomen. Any woman can have a miscarriage at this time of pregnancy. If she has CVS, this risk is increased by an extra one in 100 (1%). The result is available in 2-3 weeks. For more details, discuss CVS with your health care provider. CVS is not available in all areas.
Amniocentesis
This test can tell for sure if your baby has a condition like Down syndrome or trisomy 18. Sometimes it is used to tell if your baby has an open neural tube defect. The test is usually done between 15 and 22 weeks of pregnancy. Using ultrasound, a needle is inserted through the abdomen into the fluid around the baby and a small amount of amniotic fluid is withdrawn. The needle does not touch the baby. Any woman can have a miscarriage at this time of pregnancy, but, if she has amniocentesis, this risk is increased an extra 1 in 400 (0.2%). New studies have recently shown that the risk of miscarriage may be even lower, possibly as low as 1 in 1,600 (0.06%). The results are available in 2-3 weeks. For more details, please talk to your health care provider.
Most times, amniocentesis or CVS will show that your baby does not have Down syndrome, or trisomy 18, but these tests cannot find every condition. Even after a normal result, there is a chance of having a baby with a different condition such as a hole in the heart or mental disability.
Remember that most babies are born healthy.
A word about unexpected news:
If you have diagnostic testing and the results confirm that your baby has Down syndrome, trisomy 18 or open neural tube defect, genetic counsellors are available to help you discuss your options: continuing the pregnancy, adoption or having an abortion. Making a decision is not easy. Genetic professionals can help with finding resources such as support groups that may be helpful to you during and after your decision-making. There are health care providers available to help you and offer support no matter what decision you make.
The choice is yours.
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