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Most Common Anomalies Detected Through Prenatal Tests
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Definitions and Symptoms
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Risk Factors
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Appropriate Prenatal Tests
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Trisomy 21 - Also referred to as Down Syndrome
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This genetic anomaly occurs at conception when the fetus receives three
copies of chromosome 21, rather than two.
Trisomy 21 gives rise to intellectual and physical handicaps (including cardiac disorders) for which it is
impossible to predict the degree of severity. All pregnant women can bring a pregnancy to term in which the
fetus has Down Syndrome and there is no curative treatment.
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Risk increases
as a function
of maternal age.
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Combitest® screening done during the first and/or second trimester of pregnancy.
Diagnosis made through Amniocentesis and Amnio-Express®.
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Trisomy 18 - Also referred to as Edward's Syndrome
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Trisomy 18 also occurs at conception. It is the result of three copies of
chromosome 18 in the fetus, rather than two.
In almost all cases the fetus does not survive to birth.
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Risk increases
as a function
of maternal age.
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Combitest® screening done during the first and/or second trimester of pregnancy,
Diagnosis made through Amniocentesis and Amnio-Express®.
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Trisomy 13 - Also referred to as Patau's Syndrome
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Trisomy 13 is a rarer anomaly than trisomy 21 and 18.
Most affected fetuses die in utero or shortly after birth. Those who survive suffer severe physical and
mental disabilities.
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Risk increases
as a function
of maternal age
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Though strong suspicions may arise during an ultrasound or from the Combitest®, a formal trisomy 13
diagnosis can only be made through Amniocentesis and Amnio-Express®.
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Numerical Anomalies of Sex Chromosomes These consist of XXY (Klinefelter's Syndrome) and XO (
Turner's Syndrome) anomalies.
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Numerical anomalies of XO type sex chromosomes can lead to severe developmental problems in the fetus
or to its death before the term of the pregnancy or at birth.
With regards to numerical anomalies of XXY type sex chromosomes, the first symptoms will generally
manifest themselves in young men at puberty (infertility and male hormone deficiency).
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No specific
risk factors.
No increase
in risk
due to
maternal age.
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Diagnosis made through Amniocentesis and Amnio-Express®.
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Neural Tube
Defects
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Neural Tube Defects occur when the fetus' brain or spinal cord does not develop normally from the onset
of the pregnancy. The two major neural tube defects are:
Spina bifida which is characterized by a faulty closure of the bone structure surrounding the spinal
column. This can lead to physical and mental disabilities varying in severity according to the lesion.
Certain individuals with spina bifida can lead active lives while others are unable to walk and may suffer
from incontinence.
Anencephaly which is characterized by the absence of a large part of the skull and brain leading to
the death of the fetus before or shortly after birth.
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Folic Acid
Deficiency.
Family History.
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Most neural tube defects can be detected with an ultrasound in the second trimester and with the
Combitest® in the second trimester of pregnancy (from 15 weeks).
Nevertheless anencephaly can be detected during the first trimester nuchal translucency scan.
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