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Prenatal Genetic Screening and Counseling

August 10, 2013 by HealthyFamilies BC

couple looking at prenatal screening test results


If you wonder about your chances of having a healthy baby, talk to your healthcare provider about prenatal genetic screening - as early in your pregnancy as possible.

The sooner you start, the more options you'll have.

Prenatal genetic screening isn't mandatory. It's up to you to decide if you want it. You can also ask your healthcare provider about genetic counseling.Prenatal genetic screening is a blood test that tells you the chance of your baby having Down syndrome, trisomy18 or an open neural tube defect.

Down Syndrome:

Down syndrome is a genetic condition in which a baby has 47 chromosomes instead of 46. It's is the most common chromosome problem. People with Down syndrome have mild to moderate mental delays and a higher chance of some health problems. Each person with Down syndrome is different and there's no way to predict how serious any problems will be.


This is a rare chromosomal disorder in which all or a critical region of chromosome 18 appears three times (trisomy) rather than twice in the body's cells. Symptoms and findings vary widely from case to case.  In many affected infants, abnormalities may include growth deficiency, feeding and breathing difficulties, developmental delays, mental retardation, physical malformations and structural heart defects at birth.

Open Neural Tube Defect:

An open neural tube defect occurs when the brain or spinal cord doesn't form properly. The most common type is spina bifida, which may cause both physical and mental disabilities. Another neural tube defect, anencephaly, involves the brain and is fatal. A baby with anencephaly will be stillborn or die shortly after birth.

It’s important to remember:

  • Most prenatal screening show a low probability for down syndrome, trisomy 18 and open neural tube defect.
  • Although some women will screen positive, most won’t have a baby with one of these conditions.
  • Prenatal screening detects most babies with these conditions, but not all.
  • Sometimes prenatal screening may detect other medical conditions in your baby.
  • No test can detect every type of physical or mental condition.

Prenatal Genetic Screening Tests:

1. Nuchal Translucency (NT) Ultrasound 

This test is performed around 10 to 14 weeks. The ultrasound looks at the tiny, fluid filled space at the back of your baby's neck.

If it’s available in your area, you may be offered an NT ultrasound along with blood tests. If the ultrasound shows an increased risk, follow-up tests like an amniocentesis may be offered. Although the NT ultrasound gives more information for the screen result, the blood tests are very good screens on their own.

2. Amniocentesis

This diagnostic test is a very accurate method of finding genetic abnormalities. It’s performed with the guidance of an ultrasound, usually between 15 and 18 weeks.

You may be offered an amniocentesis if you are 40 or older, have not had any screening done before your 21st week of pregnancy, or if your prenatal genetic screening blood tests or ultrasound showed that your baby has a higher chance of having an abnormality.

A needle is used to remove a small amount of amniotic fluid through your abdomen. Test results will be available within one to three weeks. There is a small risk of miscarriage with this procedure.

For more information, talk to your healthcare provider or visit the BC Prenatal Genetic Screening Program website.

Resources and Links:

HealthLink BC: High Risk Pregnancy
HealthLink BC: Birth Defects Testing
HealthLink BC: First-Trimester Screening for Birth Defects
HealthLink BC: Amniocentesis
HealthLink BC: Should I have Amniocentesis


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