Many Quebec doctors are protesting against a new test for prenatal diagnosis of trisomy 21, otherwise known as Down syndrome. It is now available for free in the Quebec City region and will be eventually offered in other regions.
Despite protests by doctors, health authorities approved this screening which consists of two blood tests, one between the 10th and 13th weeks of pregnancy and the second between the 14th and 16th weeks of pregnancy. It can detect 75% of cases. If a test is positive, the result must be confirmed by amniocentesis.
According to doctors, however, there are better ways in the private sector, including an ultrasound where the doctor evaluates the nuchal translucency. This method is widely used in France and Denmark and detects 96% of cases.
The new test has a false positive rate of 4.8% and the acceptable Canadian standard is 3%. So, there is concern that this increases the number of amniocentesis for women and also the number of healthy babies who may be lost. The risk of miscarriage after amniocentesis is 0.25 to 0.5%.
Older pregnant women have a greater chance of having a baby with Down syndrome. So, at age 20, the odds of having a child with trisomy 21 are 1 in 1528, but when a woman reaches 45, the odds are 1 in 28.