Santé et Services sociaux Québec.

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Removal of a small amount of the amniotic fluid surrounding the foetus using a small-gauge needle inserted into the pregnant woman’s abdomen under ultrasound guidance (The amniotic fluid contains foetal cells that are grown in a culture medium so that the foetal chromosomes can be analyzed.)


An organized structure containing the hereditary determinants (genes) of an organism (Humans have 23 pairs of chromosomes, or 46 in all.)

family (medical) history

Information about diseases or disorders from which family members of the person being examined have suffered.


Number of new cases of a disease, or a chromosome abnormality like trisomy 21, during a given period in a given population.


A procedure that may affect the organism being studied. (For example, amniocentesis is an invasive medical technique that involves a certain risk of complications up to and including miscarriage or the loss of the baby.)


Photographic representation of the complete set of an individual’s chromosomes. (The karotype describes the number and structure of an individual’s chromosomes.)


Predictive element that can be observed and used to evaluate the probability that an event will occur (In prenatal diagnosis procedures, markers can be used in prenatal trisomy 21 and other chromosome abnormality screening tests. These markers can be biochemical substances (proteins and/or hormones) from the baby and/or placenta that are also found in the mother’s blood, or they can be ultrasound images of the baby.)

muscle tone

Slight, partial contraction of muscles at rest due to continuous reflexive stimulation by their motor nerves.


A highly vascularized, spongy, fleshy mass that is connected to the uterus and communicates with the baby via the umbilical cord.

sonography (ultrasound)

Medical technique that uses the reflection of ultrasound by body structures to produce images of internal tissues and organs.


Presence of a third chromosome in addition to the two chromosomes of a pair.