• Prenatal screening is a way for you to determine the chance your baby may or may not have trisomy 21 (Down syndrome) or trisomy 18. Anyone may have a pregnancy with trisomy 21 or trisomy 18, regardless of their family history. This chance increases with the age of the mother (or the age of egg donor).

• Sometimes prenatal screening can tell you about the chance for other genetic conditions, such as trisomy 13 and sex chromosome differences. The current guidelines in Ontario  do NOT currently recommend screening for a group of conditions called microdeletion syndromes (such as 22q11.2 deletion syndrome).

• Prenatal screening poses no risk to the pregnancy as it involves ultrasound and blood work.

• Prenatal screening is not diagnostic.  Only diagnostic testing, such as chorionic villus sampling or amniocentesis, can give you a “yes” or “no” answer about trisomy 21 and trisomy 18 during the pregnancy.

• Prenatal screening is available to all pregnant individuals in Ontario, and can be ordered through your health care provider. The routine pregnancy care you receive from your health care provider will not be affected whether or not you choose to have this screening.

Types of Prenatal Screening

Multiple Marker Screening 

Multiple Marker Screening is funded by the Ministry of Health for all pregnant individuals in Ontario. How far along you are in the pregnancy and availability in your area will determine which of two tests is possible for you. Enhanced first trimester screening (eFTS), which includes the nuchal translucency (NT) ultrasound, is preferred when possible. This option is only available in the first trimester of pregnancy. You may not be able to have enhanced First Trimester Screening if you are in your second trimester of pregnancy, or if you do not have access to ultrasound. In that situation, you can choose to have maternal serum screening (MSS) instead.

Non-invasive Prenatal Testing 

Non-invasive prenatal testing (NIPT) is the most accurate form of prenatal genetic screening, can be done after 9 or 10 weeks of pregnancy. NIPT is funded by the Ministry of Health in certain situations. If you do not meet any of the funding criteria, you can choose to pay for it out-of-pocket (private-pay).  

Some people have NIPT as their only prenatal screening test in their pregnancy. Others will start with another prenatal  screening test (eFTS or MSS), and may consider having NIPT later in pregnancy.

Options by Pregnancy Stage

Your options for screening or follow up testing will vary depending on how far along you are in the pregnancy. Which of the following statements applies to you?

• I am less than 14 weeks pregnant
• I am between 14 and 21 weeks pregnant
• I am more than 21 weeks pregnant

Expecting More Than One Baby

Learn about your options for prenatal genetic screening if you are expecting more than one baby.

Deciding if Prenatal Screening is Right for You

Would knowing whether there is a higher or lower chance to have a baby with trisomy 21 or trisomy 18 be helpful to you during the pregnancy? Some people would prefer to wait for this information until the baby is born. Others would want to know if there is a chromosome difference to help them prepare for having a child that may require special care. When there is a chromosome difference, the health-care provider may recommend changes to how the pregnancy is looked after, or the birth plan. Some individuals would consider interrupting the pregnancy if the result is confirmed by further diagnostic testing.

No one can tell you if prenatal screening is right for you. It is a personal decision and there is no right or wrong answer. All prenatal screening is optional. You might ask yourself:

• How important is it for you to know if there is an increased chance of a chromosome difference that could affect your baby's health and development?
• If your screen result is positive, how likely are you to consider more testing?
• How useful would it be for you to know about a chromosome difference before your baby's birth to prepare? When there is a chromosome difference, the health care provider may recommend changes to how the pregnancy is looked after, or the birth plan. You may wish to discuss the decision with your health care provider if you have further questions.
• What are your thoughts about continuing or ending your pregnancy if your baby has a chromosome difference?
• How would knowing or not knowing affect you emotionally throughout the pregnancy?

You may wish to discuss the decision with your health-care provider if you have further questions. If you decide you do not want these tests, you can still have ultrasounds in the pregnancy. Ultrasounds which offer valuable information about the pregnancy, beyond screening for trisomy 21 and trisomy 18. These ultrasounds will give you information such as:

• how far along your pregnancy is;
• how many babies you are carrying; and
• whether there are concerns with the baby's growth and anatomy.

Referral for Genetic Counselling

If your genetic prenatal screening results are not reassuring, or you have other concerns (such as a genetic condition in your family), you may consider talking to your health-care provider about being referred to the nearest genetics centre.