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PreNatest Plus, 1st or 2nd Trimester


Performed in the first trimester of pregnancy, a PreNatest (prenatal screening test) uses a drop of blood to assess the risk of carrying a fetus with one of the most common birth abnormalities: Trisomy 21 (Down Syndrome) and Trisomy 18. This test does not provide a definitive diagnosis for fetal chromosome abnormalities. In combination with the 1st trimester ultrasound and a nuchal translucency scan, it is used primarily to identify cases where a more invasive analysis such as amniocentesis (direct analysis [karyotype] of chromosomes in the amniotic fluid) would be indicated. PreNatest Plus categorizes the risk as low (less than a 1 in 2500 chance of having a fetus with Trisomy 21 or 18), intermediate (1 in 251 to 1 in 2500 chance) or high (1 in 250 chance). For the intermediate and high risk categories, another non-invasive test (2nd trimester PreNatest) is first proposed. Based on the results of this second test, the physician or genetic counsellor can discuss available options.

Term of the Week

Predictive medicine

Medicine that links medical knowledge with data to predict a patient’s potential health problems. Examples include artificial intelligence and genetics.