Screening

What is prenatal screening?

Prenatal screening is a
non-invasive
and safe procedure.

The results of your

screening test

will show a low or high risk that your baby has a trisomy. They only show probability, so if your probability is low, this is no guarantee that your baby does not have trisomy. By the same logic, if your probability is high, your baby does not necessarily have trisomy.

Québec Prenatal Screening Program

In accordance with the recommendations of the Society of Obstetricians and Gynecologists of Canada (SOGC) and the Canadian College of Medical Geneticists (CCMG), the Québec Prenatal Screening Program offers the prenatal screening test to all pregnant women in Quebec who so wish. The program includes two tests:

The biochemical test (with or without nuchal translucency)
The Genomic test

In this program, women are first offered a

biochemical test

(with or without

nuchal translucency ultrasound

depending on its availability in their region). Secondly,

genomic testing

is offered to women whose biochemical test results show high

probability

of trisomy. In special circumstances,

genomic prenatal testing

may also be offered as a first screening test (see box below).

Requirements for genomic testing as a first screening test

If, in a previous pregnancy, the baby had trisomy 21, trisomy 18, or trisomy 13.
If you are 40 years of age or older at the time of delivery.
If you have been given a prescription by a genetic consultant.
If you are pregnant with twins (2 babies)

Tests	Biochemical test	Nuchal translucency ultrasound	Genomic test
Definition	Consists of one blood test during pregnancy to measure the level of proteins and hormones from the baby and the placenta in the mother's blood.	Consists of measuring the thickness of the baby's neck (space between the skin and the spine) by ultrasound.	Consists of one blood test during pregnancy to analyze free fetal DNA fragments from the placenta circulating in the maternal blood.
Notes	Can detect trisomy 21 May suspect other trisomies or preeclampsia (sometimes severe maternal hypertension)	Can detect trisomy 21 May suspect other trisomies, abnormalities or malformations	Can detect trisomy 21, trisomy 18 and trisomy 13 May suspect other genetic abnormalities May suspect genetic abnormalities in the mother (rarely)