Description

The Québec Prenatal Screening Program aims to make prenatal screening for trisomy 21, trisomy 18 and trisomy 13 accessible to pregnant women and couples in Québec on a voluntary basis. There are other chromosomal abnormalities but the public program, which is based on Canadian recommendations, does not screen for them.

The Québec Prenatal Screening Program is offered free of charge in the public health network.

Screening is offered during pregnancy follow-up but is not a routine test. Your doctor or midwife must ensure that you have been given all the information you need to decide whether or not you wish to participate. This decision is entirely up to you. The professional who is providing your pregnancy follow-up must also ask you to sign the consent form if you wish to participate in the program.

Before signing the consent form, you need a clear understanding of what trisomies 21, 18 and 13 are, what information the screening tests will give you and the decisions you might have to make.

By participating in the screening program, you will be able to find out as early as possible during your pregnancy if the child you are carrying has a high probability of having one of the three trisomies. When the probability is high, additional tests are offered to confirm that your baby has one of the trisomies. If so, you may have to decide if you want to continue your pregnancy and give birth to the child or if you want to terminate your pregnancy.

In this online section, you will find all the relevant information on the Québec Prenatal Screening Program to help you decide whether or not to participate in the program.

Trisomy 21

Trisomy 21, also known as Down Syndrome, is caused by the presence of an extra chromosome in the 21st pair of the 23 pairs of chromosomes found in every cell in the human body. It is one of the most common trisomies. Trisomy 21 is not generally hereditary (more than 95% of cases) and therefore occurs at random. Less than 5% of cases are inherited.

All people with trisomy 21 have some degree of intellectual disability, varying from mild to severe. Some people may need a lot of support and guidance throughout their life, while others may have a job and lead an almost independent life. It is impossible to determine the level of autonomy and intellectual functioning that a child with trisomy 21 may develop.

Most children with trisomy 21 can walk and talk, but it takes longer for them to learn language and motor skills. The interventions and support these children receive from an early age influence their development. In addition to intellectual disability, these children may have other types of health problems, such as heart and bowel malformations or epilepsy.

People with trisomy 21 have the potential to establish deep emotional relationships and lead lives that are fulfilling both for themselves and their loved ones.

Frequency of trisomy 21

Around 1 in 770 babies is born with trisomy 21. Any pregnant woman, regardless of her age, may be carrying a child with trisomy 21. However, the probability increases with age.

The graph below shows that the probability of carrying a child with trisomy 21 increases with the woman's age. At age 20, the probability is 1 in 1,528 pregnant women, while at age 45, the probability increases to 1 in 28 pregnant women.

    Trisomy 18

    Trisomy 18, also known as Edwards syndrome, is caused by the presence of an extra chromosome in the 18th pair of the 23 pairs of chromosomes found in every cell in the human body. It is the most common trisomy after trisomy 21.

    Trisomy 18 is rare and affects approximately 1 in 4,500 babies at birth. However, nearly 95% of pregnancies in which the baby has trisomy 18 end in miscarriage or the baby’s death before birth. Any pregnant woman may be carrying a baby with this chromosomal abnormality, but the probability increases with age. Like trisomy 21, trisomy 18 occurs randomly in most cases.

    People with trisomy 18 have stunted growth before and after birth. They have an intellectual disability and severe global developmental delay. Most of these people have abnormalities of the hands and feet. Major malformations of internal organs, particularly the heart and kidneys, are common. Most babies born with trisomy 18 die shortly after birth due to severe heart and brain malformations or respiratory disorders. Only 5 to 10% survive more than a year. However, in exceptional cases, some babies reach adulthood. In all cases, babies who have trisomy 18 will receive support and comfort care or may receive some treatment, depending on the symptoms.

    Trisomy 13

    Trisomy 13, also known as Patau syndrome, is caused by the presence of an extra chromosome on the 13th pair of the 23 pairs of chromosomes found in every cell in the human body.

    Trisomy 13 affects approximately 1 in 7,000 babies at birth. Trisomy 13 is very severe and often associated with a miscarriage or multiple malformations. Over 95% of affected babies die before birth. Of the pregnancies carried to term, half the babies will die during the first month of life and 90% will die before one year from cardiac, kidney and neurological complications. In exceptional cases, the baby may live longer if it does not have any major brain malformations. Any pregnant woman may be carrying a baby with this chromosomal abnormality, but the probability increases with age.

    Trisomy 13 is characterized by facial abnormalities and limb deformities, very severe neurological problems and brain, heart and urogenital malformations. Intellectual and developmental delays are severe.

    Generally, medical care is limited to providing support and comfort care.

    Eligibility and cost

    The Québec Prenatal Screening Program is offered free of charge to all pregnant women who have a Régie de l'assurance maladie du Québec (RAMQ) health card. Some women with special status may also have access to it. However, there may be a fee for nuchal translucency measurement if it is done at a private clinic.

    Special conditions

    Women who have a multiple pregnancy, that is, who are carrying more than one baby, are not eligible for the Québec Prenatal Screening Program due to its current limitations. Women who are pregnant with twins or triplets, for example, must talk to their doctor to find out about the option available to them.

    Procedure

    The Québec Prenatal Screening Program includes:

    • A biochemical test, including nuchal translucency measurement if possible;
    • A non-invasive prenatal genomic test (NIPT) or an amniocentesis to investigate further if the biochemical test indicates a high probability of fetal trisomy.

    Keep in mind that you can end your participation in the program at any time and at any stage.

    The figure below shows the different stages of the prenatal screening program, including the times when you will have to make a decision.

    Stage 1: Biochemical test (with or without nuchal translucency measurement)

    The biochemical test is a screening test that, with or without nuchal translucency measurement, reveals the probability of giving birth to a baby with trisomy 21, be it low or high.

    As part of this test, a similar probability calculation is done for trisomy 18. The results for trisomy 13 are comparable to those for trisomy 18. This means that they cannot be distinguished at this stage of screening.

    Blood tests

    The biochemical test is used to measure proteins or hormones from the baby in the mother’s blood. The test involves having two blood tests during your pregnancy:

    • the first blood test is done between weeks 10 and 13;
    • the second blood test is done between weeks 14 and 16.

    Both blood tests are important and ensure more reliable results than a single blood test. It is therefore preferable to have the two blood tests done at the right time if you decide to participate in the Québec Prenatal Screening Program. There is no risk for the pregnancy associated with blood tests.

    First trimester ultrasound

    You will be proposed a first trimester ultrasound between weeks 11 and 14 to check how far along you are in your pregnancy and identify possible abnormalities in your baby. This ultrasound is used to assess how long you have been pregnant in order to calculate the probability of having a baby with a trisomy.

    The nuchal translucency measurement by ultrasound might also be proposed. It is performed between weeks 11 and 13. It measures the thickness of the fluid build-up at the back of the baby’s neck. In babies with trisomy 21, the fluid build-up is often thicker than normal. When available, the nuchal translucency measurement is combined with the results of the biochemical test to calculate the probability of trisomy.

    Biochemical test results (with or without nuchal translucency measurement)

    The results of the two blood tests and nuchal translucency measurement (if available) will indicate whether the probability of trisomy 21 is low or high:

    Low probability (less than 1 in 300)

    It is unlikely that your baby has trisomy 21 and no additional tests are necessary (more than 95% of women get this result when they have the biochemical test).

    However, this result does not guarantee that your baby does not have trisomy 21. Considering the natural differences between individuals and the limitations of prenatal screening, biochemical tests and nuchal translucency measurement cannot detect all cases of trisomy 21.

    High probability (equal to or higher than 1 in 300)

    You may be carrying a child with trisomy 21 (3 to 4% of women get this result when they have the biochemical test). You will be proposed follow-up to confirm whether or not there is a trisomy. This result does not necessarily mean that the baby will have trisomy 21.

    As part of this test, a similar calculation of probability calculation is done for trisomy 18. The results for trisomy 13 are comparable to those for trisomy 18. This means that they cannot be distinguished at this stage of screening.

    At this point, your doctor or midwife will recommend that you move on to stage 2 of the program. The decision is yours.

    Stage 2: Non-invasive prenatal genomic test (NIPT) or amniocentesis

    Depending on the results you receive in stage 1 of the program, your doctor or midwife might offer you the non-invasive prenatal genomic test or rather that you go straight to amniocentesis. You will be given the explanations and information you need to decide which option is best for you.

    The “Non-invasive prenatal genomic test and amniocentesis: characteristics” section, presented below, summarizes the information on these two tests.

    Non-invasive prenatal genomic test (NIPT)

    You will be proposed the non-invasive prenatal genomic test if you have a high probability of having a baby with trisomy 21 (or trisomy 18) based on the biochemical test. The test involves taking a sample of the mother’s blood in order to analyze DNA fragments from the placenta.

    The genomic test (NIPT) screens for trisomy 21, trisomy 18 and trisomy 13.

    This test is offered because it is reliable and safe (there is no risk of miscarriage compared with amniocentesis).

    You might also be proposed this test right away (instead of the biochemical test) if you are in one of the following situations:

    • you have had a pregnancy in which the baby had trisomy 21, trisomy 18 or trisomy 13;
    • you will be 40 years old or older at the time of delivery;
    • the test is prescribed following a consultation in genetic medicine.

    Non-invasive prenatal genomic test (NIPT) results

    Low probability

    There is a very low probability that your baby has one of the trisomies, even if the result of the biochemical test showed a high probability initially. This result is very reliable (over 99%) and there is no need for further investigations.

    High probability

    It is likely that your baby has one of the three trisomies. However, this result is not 100% certain and only a diagnostic test (amniocentesis) can determine with great certainty whether your baby has one of the trisomies.

    Non-invasive prenatal genomic test has some limitations:

    • It does not identify all babies with one of the tested trisomies.
    • It does not rule out the possibility of a false-positive result. In fact, there is a possibility that the baby does not have one of the trisomies even if the result is positive. For this reason, amniocentesis is offered in the event of a positive result.
    • It does not work in a small percentage of women. In this situation, the health professional who is providing your pregnancy follow-up can discuss your options, in particular amniocentesis, with you.
    • It does not screen for all genetic diseases that cause abnormalities, intellectual delays or autism.

    Amniocentesis: a diagnostic test

    Amniocentesis is a diagnostic test that you will be proposed if the non-invasive prenatal genomic test results shows a high probability for trisomy 21, trisomy 18 or trisomy 13. Some women or couples may want to go straight to amniocentesis, without doing the genomic test, despite the risks involved. This possibility can be discussed with the professional responsible for your pregnancy follow-up.

    The test involves inserting a fine needle into your abdomen to collect a small quantity of the amniotic fluid surrounding the baby in the uterus. This fluid contains the baby’s cells and amniocentesis allows the chromosomes in these cells to be analyzed. The test can be performed as of the 15th week of pregnancy.

    Amniocentesis is a diagnostic test that can confirm with great certainty whether your baby has one of the three trisomies, just as it can confirm with the same certainty that your baby does not have one of these trisomies.

    Possible complications associated with amniocentesis

    Amniocentesis carries risks for the pregnancy, the main one being miscarriage. The risk of miscarriage after amniocentesis is around 1 in 300. Therefore, the test is offered only to pregnant women who have a high probability result on the screening test. Some minor complications have also been observed. The most common (2 to 5% of cases) are:

    • loss of a small amount of amniotic fluid;
    • uterine contractions;
    • abdominal pain.

    Amniocentesis results

    Absence of trisomy

    Your baby does not have trisomy 21, trisomy 18 or trisomy 13. This result is very reliable.

    Presence of trisomy 21

    Your baby has trisomy 21. This result is very reliable. 

    You must decide if you wish to:

    • Continue your pregnancy and prepare to be the parent of a child with trisomy 21;
    • Continue your pregnancy and give the child up for adoption;
    • Terminate your pregnancy and deal with the grief that might cause.

    The decision must be made when there is no way to predict the severity of the intellectual disability or the level of autonomy your child might have and without knowing if your child has physical malformations or other health problems.

    Presence of trisomy 18 or trisomy 13

    Your baby has trisomy 18 or trisomy 13. This result is very reliable.

    You must decide if you wish to:

    • Continue the pregnancy;
    • Terminate the pregnancy.

    The decision must take into consideration the severity of the malformations associated with these trisomies and the fact that 90% of affected newborns will not live longer than a year. The decision must also be made when it is impossible to predict with certainty the condition of your baby at birth.

    Non-invasive prenatal genomic test and amniocentesis: characteristics

    Non-invasive prenatal genomic test:
    • If the test result is negative, the result is over 99% reliable;
    • If the test result is positive, the result is probable but must be confirmed;
    • The test poses no risk to pregnancy;
    • The wait time for results is 5 to 10 days.
    Amniocentesis (diagnostic test)
    • The result of this test, whether negative or positive, is the most reliable result;
    • The test is associated with a risk of miscarriage (1 in 200 cases [0.5%] to 1 in 500 cases [0.2%]);
    • The wait time for results is around 3 days with a rapid diagnostic test.

    Stages of prenatal screening

    Voluntary participation

    Participation in the Québec Prenatal Screening Program is voluntary. The decision is personal and entirely up to you. To help you decide, you can discuss it with your partner, your family and friends, the health professional responsible for your pregnancy follow-up, a genetic professional or groups for parents of children with a trisomy.

    For clarity, you could also ask yourself the following questions:

    • Do I want to know my probability of having a baby with trisomy 21, trisomy 18 or trisomy 13?
    • How will I react if the result of the screening tests is showing a high probability of trisomy?
    • Do I want to have amniocentesis if the result of the screening test is showing a high probability of trisomy, despite the risk of a miscarriage?
    • Do I want to terminate my pregnancy if I find out my baby has trisomy 21, trisomy 18 or trisomy 13?
    • Do I want to continue my pregnancy if I find out my baby has trisomy 21, trisomy 18 or trisomy 13, and raise my child or, alternatively, give it up for adoption?

    Remember that the program is voluntary and that you can choose whether or not to have the screening tests depending on your situation, your values and what you want. This decision is personal and the reasons behind your choices are your own. You can also refuse to have amniocentesis if it is offered to you. If you want, you can also decide to withdraw from the program at any time.

    If you decide to participate in the Québec Prenatal Screening Program, your doctor or midwife will have you sign a consent form and will help you with the process.

    If you decide not to participate in the Québec Prenatal Screening Program, you do not have to sign anything but your health professional must note your refusal. Your doctor or midwife will answer your questions and tell you about the stages of the pregnancy follow-up.

    Help and support

    Deciding whether or not to participate in the Québec Prenatal Screening Program is not necessarily easy. Deciding to terminate or carry a pregnancy to term knowing that the baby has a trisomy is even harder.

    If the outcome of your participation in the program means that you have to make a choice between continuing or terminating your pregnancy, you might need help.

    Your doctor or midwife can refer you to psychology services that will support you in your reflection. Do not hesitate to discuss this choice with your family and friends or with a health professional. You can also contact groups of parents who have children with trisomy; this might help you make the decision that is best for you.

    To find out the contact information of groups in your region, ask the professional you are seeing for your pregnancy follow-up.