Ontario Prenatal Screening
Early on in your pregnancy, you can decide whether or not you would like to have
prenatal screening. These tests are optional - it is your choice whether or not to have
them. The purpose of this Guide is to give you information to help with your decision.
What are prenatal screening tests?
- These are blood tests, sometimes with an ultrasound, which are done starting at 11 weeks of pregnancy.
- They are SCREENING tests, which means they tell you your CHANCE of having a baby with Down syndrome, trisomy 18 or an open neural tube defect.
- Screening tests cannot tell you for sure whether or not your baby has one of these three conditions, only the chance of this.
- To find out for sure, you would have to decide whether to have a DIAGNOSTIC test.
- Prenatal screening cannot find every birth defect.
Prenatal Screening is Available for:
- Down Syndrome
- Trisomy 18
- Open Neural Tube Defects
Down syndrome
People with Down syndrome usually have mild to moderate intellectual delay. Individuals with Down syndrome may have a greater incidence of health conditions than the average person such as heart, stomach, bowel, thyroid, vision and hearing problems. Treatment is available for many of these conditions. Each person with Down syndrome is different. There is no way to test how serious the disabilities will be. People with Down syndrome generally live into their fifties. In general, about one in 1000 births has Down syndrome. The chance of having a child with Down syndrome increases with the mother’s age.
Trisomy 18
Babies with trisomy 18 have both mental and physical disabilities. Many pregnancies with trisomy 18 will miscarry. Most babies born with trisomy 18 do not survive past the first few months of life. In general about one in 6,000 births has trisomy 18. The chance of having a child with trisomy 18 increases with the mother’s age
Open Neural Tube Defects
These conditions occur when the brain or spinal cord does not form properly.
An open neural tube defect involving the spinal cord is called ‘spina bifida’. Spina bifida causes physical disabilities such as difficulty walking, and difficulty controlling the bladder and/or bowel. People with spina bifida may also have mental disabilities. Treatment can help with many of the physical disabilities.
An open neural tube defect involving the brain is called ‘anencephaly’. A baby with anencephaly will be stillborn or die shortly after birth. In Canada, the chance of having a baby with an open neural tube defect is about 1 out of every 2000 births. The chance of a child being born with this condition does not increase with the mother’s age.
Family history:
Other tests or genetic counselling may be suggested if you or your partner have a close family member who was born with a birth defect or has a serious health problem.
Please talk to your health care provider for more information.
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