LibGuides: Year 10 Science: Genetic Testing: Prenatal Testing

Prenatal Screening

Prenatal screening is offered for all pregnancies in Australia.

Screening is used to identify an increased chance of the baby having:

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Types of Prenatal Screening

Nuchal Translucency Scanning
A scan looking for features that may indicate a risk of chromosomal abnormality, such as Down Syndrome.

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Non-Invasive Prenatal Testing (NIPT)
NIPT is a blood test used to screen for a high chance of the baby having the following conditions:
- Down syndrome (also called trisomy 21)
- Edwards syndrome (trisomy 18)
- Patau syndrome (trisomy 13)
- Turner syndrome

How do the Screening tests work?

First Trimester Screening Tests
What doctors are looking for in the Nuchal Translucency Scan and NIPT blood test.

Prenatal Screening and Testing

Two main types of prenatal testing are performed during pregnancy. The first type of testing is known as screening. Screening tests are used to identify women with an increased chance to have a baby with certain chromosomal abnormalities.

Results that reveal a chance over a certain cutoff level are called “positive results,” and these women are offered further testing.

The second type of prenatal testing is known as diagnostic testing because these tests can determine definitively if the developing fetus has a certain genetic condition or birth defect.

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Chorionic Villus Sampling

Chorionic Villus Sampling (CVS) involves taking a small sample of the placenta. The sample is removed using a slender needle inserted through the abdomen. The tissue (chorionic villi) is then examined in a laboratory.

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Amniocentesis

Amniocentesis

Amniocentesis involves taking a sample of amniotic fluid and testing the DNA from the cells for diagnosis of certain conditions.

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Prenatal Testing

Prenatal testing is used to confirm the diagnosis of a genetic disorder or chromosomal abnormality.

It is offered in high risk pregnancies, such as:

following a high risk prenatal screening test result
where parents already have a child with a genetic or chromosomal condition
if both parents are carriers of a particular condition
for women aged 35-37 years of age or over when your baby is due

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Types of Prenatal Diagnostic Testing

Chorionic villus sampling (CVS)
What CVS is, what it can detect, and how it is performed.

Amniocentesis
What amniocentesis is, what it can detect and how it is performed.

Down's Syndrome

Down's Syndrome
Down syndrome, also called Down’s syndrome, trisomy 21, or (formerly) mongolism, congenital disorder caused by the presence in the human genome of extra genetic material from chromosome 21.

The physical and cognitive impacts of Down syndrome range from mild to severe. Some common physical signs of the disorder include a small head, flattened face, short neck, up-slanted eyes, low-set ears, enlarged tongue and lips, and sloping underchin. Other characteristics of the disorder may include poor muscle tone, heart or kidney malformations (or both), and abnormal dermal ridge patterns on the palms of the hands and soles of the feet. Intellectual disability occurs in all persons with Down syndrome and usually ranges from mild to moderate. Congenital heart disease is found in about 40 to 60 percent of people with Down syndrome.
Source: Britannica