What Is a Chromosome Test on Babies for

Testing for Down's syndrome and other chromosome abnormalities

Information for expectant parents

What are chromosome abnormalities?

Chromosomes carry our individual genetic textile (genes). Our bodies are made up of billions of cells, and in each cell there are 23 pairs of chromosomes. Actress or missing chromosomes may cause abnormalities that tin can bear on a babe's development. The almost common chromosome abnormality affecting newborns is Down's syndrome which occurs in around 1 in 500 to 600 pregnancies.

Down syndrome (trisomy 21)

Downwardly syndrome (also known equally trisomy 21) is a genetic condition—it is non an illness or a disease. Downwards syndrome is caused by the occurrence of an extra chromosome; chromosome 21. This results in a range of physical features, health problems, developmental delay and some level of intellectual disability. In about cases there is no family history of Down syndrome as it ordinarily occurs randomly. Other chromosome abnormalities such equally Edward syndrome (trisomy xviii) and Patau syndrome (trisomy 13) occur less oftentimes than Down syndrome but have more severe effects on the baby. Chromosome abnormalities cannot be reversed in one case they occur.

What tests are available?

• Screening exam—looks for signs that a infant may be at an increased risk of having a chromosome abnormality, such as Down syndrome. A screening test cannot determine that a baby definitely has a certain abnormality. Screening tests do not deport whatever hazard to the mother or baby.
• Diagnostic test—tin confirm whether or non the babe is afflicted by certain chromosomal abnormalities. Diagnostic tests conduct a small hazard of pregnancy loss.

Screening tests

The Start Trimester Combined Screen (FTCS)

The FTCS involves an ultrasound scan of the baby at 11 to 13 weeks gestation (nuchal translucency scan) and a blood test from the mother at 10 to xiii weeks gestation (Papp-A and BHcg). The test combines the mother's age (the age of the egg if using a donor egg), weight, ethnicity, smoking status, blood examination results and ultrasound findings to signal a level of chance for Down syndrome (trisomy 21), Edward syndrome (trisomy 18) and Patau syndrome (trisomy 13). Other markers such equally the nasal os may be included in the assessment.

The level of adventure is described as a number east.g. 1 in 100 which is the aforementioned as a ane per cent take chances. A result is deemed high risk when it is more than than one in 300 and depression risk when less than ane in 300.

Effectually five per cent of significant women (one in 20) who have the FTCS volition be given a 'high risk' result but the majority of them will not exist carrying a baby with a chromosome abnormality. Within this 'high risk' group will exist most cases of Downwardly syndrome, Edward syndrome and Patau syndrome.

Effectually 95 per cent of pregnant women (19 in 20) who have the FTCS volition exist given a 'low risk' consequence. Within this 'low risk' group there will nonetheless be some cases of Down's syndrome, Edward syndrome and Patau syndrome.

An ultrasound scan image showing the area at the back of the neck called the 'nuchal translucency'

The triple examination or second trimester maternal serum screen

The triple exam is a blood examination performed in the 2d trimester of pregnancy at xv to 20 weeks gestation. It measures the levels of certain hormones in the mother'southward blood to assess the adventure of Down syndrome, Edward syndrome, Patau syndrome and also neural tube defects (e.g. spina bifida). Dating the pregnancy past ultrasound is recommended for the triple test.

Around five per cent of pregnant women (1 in 20) who accept the triple test will exist given a 'high chance' result but the bulk of them will non be carrying a baby with a chromosome abnormality. Within this 'high adventure' grouping will exist about cases of Downwards syndrome.

Effectually 95 per cent of significant women (nineteen in 20) who have the triple examination will exist given a 'low take chances' result. Within this 'depression risk' group there will yet exist some cases of Down syndrome.

If the risk for a neural tube defect (spina bifida) is 'high', an ultrasound scan is recommended every bit the diagnostic test.

Non-invasive prenatal testing (NIPT)

NIPT involves taking a sample of blood from the pregnant adult female. This tin can be done from 10 weeks of pregnancy onwards. The blood sample is evaluated for the babe'southward DNA to determine a level of gamble for Downwardly syndrome (trisomy 21), Edward syndrome (trisomy 18) and Patau syndrome (trisomy xiii).

It is important to understand that NIPT is a screening and not a diagnostic test. If the result comes back indicating a low take chances for trisomies 21, eighteen and xiii, it is very unlikely (less than or equal to 0.1% risk) that your baby has ane of these disorders. If the result comes back indicating a high gamble of trisomy, invasive testing with amniocentesis or chorionic villus sampling may exist offered. Furthermore, this test does not provide information almost structural abnormalities. However, the do good of the test is that information technology is non-invasive and not associated with an increased take chances of pregnancy loss.

NIPT is offered to high-run a risk women including those aged 35 years and over, those with an abnormal ultrasound, a personal or family unit history of aneuploidy, and an abnormal CFTS or triple exam. Withal, NIPT can as well be performed for low-risk women.

This test tin can be performed for both singleton and twin pregnancies, although CFTS is the preferred test for twin pregnancies. For triplets and more, the nuchal translucency (NT) test and measurement of the nasal bone is the preferred option.

The turnaround time for NIPT results is upwardly to 14 days. Upwardly to five per cent (ane in 20) of NIPT tests may not return a issue due to insufficient quantity of fetal Deoxyribonucleic acid in the maternal blood sample.

Diagnostic tests

Chorionic Villus Sampling (CVS) and amniocentesis are both diagnostic tests that can ostend whether or not a babe has a chromosome aberration. They involve sampling of the placenta (CVS) or amniotic fluid (amniocentesis) and carry a take a chance of pregnancy loss of betwixt 0.v and 1 per cent. For further information delight run into Mater'south brochure: Chorionic Villus Sampling (CVS) and Amniocentesis.

Ofttimes asked questions

Should I have more than one screening examination?

No. A screening examination should only be performed once. The same screening test should not be repeated. A triple test is not required if a FTCS has already been performed.

Are there any benefits to testing?

Informing the parents almost potential bug during the pregnancy is a normal role of providing good antenatal care. Babies with chromosome abnormalities may crave monitoring earlier birth for specific abnormalities e.one thousand. cardiac malformations. In some circumstances, birth may be required in a specialised middle. Knowledge of a chromosome abnormality affecting the unborn infant may too influence when and how the babe is born. Information virtually health problems affecting their unborn babe gives parents the opportunity to seek farther information, counselling and back up.

Are there whatsoever downsides to testing?

Parents should consider the risks and benefits of all antenatal tests before proceeding. Testing for health problems affecting the unborn baby may create an unwelcome level of anxiety for some parents and relief for others. Diagnostic testing carries a small take chances of pregnancy loss that has to be weighed against the potential benefits of knowing early in pregnancy that a baby might have health problems. We encourage you to ask your wellness provider questions nigh the possible risks and benefits of any suggested treatment or tests, equally well as the range of possible outcomes.

What most the 18 to 20 week scan?

It is recommended that all women take an ultrasound in pregnancy betwixt eighteen+0 to 20+6 weeks to check for structural abnormalities, amniotic fluid volume and placental location. The 18 to 20 week scan is non recommended as a screening test for Down syndrome due to its poor functioning.

What if testing indicates a trouble?

Your health provider will talk over the results of the tests with you. They tin also arrange referral for further counselling or additional testing if required.

Can all abnormalities exist ruled out?

The majority of babies are salubrious at birth. While some weather such equally Down's syndrome tin exist tested for during pregnancy, non all abnormalities tin can be ruled out. If you have concerns about whatever specific conditions e.g. those that might be present in a family member, delight talk over this with your wellness care provider.

How tin can I arrange to have testing?

The beginning affair to do is to hash out available testing options with your health intendance provider. FTCS is performed in almost local radiology practices accredited to perform the nuchal translucency scan. The nuchal translucency scan commonly incurs an out-of-pocket expense.

Mater Middle for Maternal Fetal Medicine (MFM)

As a tertiary referral centre MFM provides diagnostic testing by CVS or amniocentesis. Pre and postal service-procedure counselling is included as office of our service. Referrals for diagnostic testing past CVS or amniocentesis can exist faxed to 07 3163 1890. A referral from a doctor is required to access services provided by the centre. Bulk-billing is available for public patients referred from Queensland Health Hospitals and those holding Wellness Intendance cards. An judge of fees can be obtained by contacting our reception staff on 07 3163 1896.

Contact details

Mater Eye for Maternal Fetal Medicine
Level seven
Mater Mothers' Hospital
Raymond Terrace
South Brisbane Qld 4101
Phone: 07 3163 1896
Fax: 07 3163 1890
Website: world wide web.matermothers.org.au

Further information and support

Genetic Health Queensland
Phone: 07 3636 1686
Website: http://www.health.qld.gov.au/ghq/default.asp

Down's syndrome Clan of Qld
Phone: 07 3356 6655
Website: world wide web.dsaq.org.au

Middle for Genetics Instruction
Website: www.genetics.edu.au

Fetal Medicine Foundation (Great britain)
Website: www.fetalmedicine.com

Mater acknowledges consumer consultation in the development of this patient information.

Mater Doc Num: PI-CLN-430139

Last modified 18/10/2017.
Consumers were consulted in the evolution of this patient information.
Last consumer engagement date: 22/8/2017

For farther translated health information, you can visit healthtranslations.vic.gov.au/ supported by the Victorian Department of Health and Human Services that offers a range of patient data in multiple languages.

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What Is a Chromosome Test on Babies for

Source: http://brochures.mater.org.au/brochures/mater-mothers-hospital/testing-for-down-syndrome-and-other-chromosome-abn