Dna down syndrome test

Prenatal Testing for Down Syndrome | Patient Education

Screening tests

All pregnant individuals in California have access to California prenatal screening (CA PNS), also called sequential integrated screening. This noninvasive process is carried out in two steps.

In the first step, which is performed when the pregnancy is between 10 and 14 weeks, a blood sample is taken from the pregnant person and a nuchal translucency ultrasound is performed to measure the fluid at the back of the baby's neck. If the blood test is scheduled prior to the ultrasound, we can provide those results at the end of your ultrasound appointment. The blood test results, nuchal translucency measurement and pregnant person's age are together used to estimate the risk for Down syndrome and trisomy 18 (a genetic condition, also called Edwards syndrome, that affects fetal development).

The second step is a test performed with a blood sample from the pregnant person when the pregnancy is between 15 and 20 weeks. When the results of this blood test are combined with the results from the first trimester blood test and nuchal translucency ultrasound, the detection rate for Down syndrome increases. This test also provides a personal risk assessment for having a fetus with trisomy 18, Smith-Lemli-Opitz syndrome (a genetic condition that can slow growth and cause intellectual disability), an open neural tube defect (a problem with the formation of the embryo's nervous system, such as spina bifida) or an abdominal wall defect (an abnormal opening in the abdomen).

Diagnostic tests

Amniocentesis, chorionic villus sampling (CVS) and ultrasound are the three primary procedures for diagnostic testing.

Amniocentesis is the test we most commonly use to identify chromosomal problems, such as Down syndrome. (In at-risk fetuses, it can be used to detect other genetic diseases, such as cystic fibrosis, Tay-Sachs disease and sickle cell disease.)

An amniocentesis procedure for genetic testing is typically performed when the pregnancy is between 15 and 20 weeks. Under ultrasound guidance, a needle is inserted through the abdomen to remove a small sample of amniotic fluid. Cells from the fluid are cultured and a karyotype test – an analysis of the cells' chromosomal makeup – is performed. It takes about two weeks to receive the results. Amniocentesis detects most chromosomal disorders with a high degree of accuracy.

There is a low risk of miscarriage as a result of amniocentesis – about 1 in 900. Miscarriage rates for amniocentesis performed at UCSF are extremely low.

Like amniocentesis, chorionic villus sampling is most commonly used to identify chromosomal problems, such as Down syndrome. (It can also be used to detect other genetic diseases – including cystic fibrosis, Tay-Sachs disease and sickle cell disease – in at-risk fetuses.) The main advantage over amniocentesis is that CVS is done much earlier in pregnancy, at 10 to 12 weeks rather than 15 to 20 weeks.

CVS involves removing a tiny piece of tissue from the placenta for analysis. Under ultrasound guidance, this sample is obtained either with a needle inserted through the abdomen or a catheter inserted through the vagina and into the cervix (outer end of the uterus). The tissue is cultured and a karyotype test of the cells' chromosomal makeup is performed. It takes about two weeks to receive the results.

While it can provide information earlier in pregnancy than amniocentesis, CVS does not detect spinal cord defects. However, we can screen for spinal cord defects later in the pregnancy using expanded alpha-fetoprotein (AFP) blood testing or ultrasound.

There is a low risk of miscarriage as a result of CVS – about 1 in 450. Miscarriage rates for CVS procedures performed at UCSF are very low.

While the primary purpose of ultrasound is to determine the pregnancy's status – due date, size of the fetus and whether there's more than one baby – ultrasound can also provide some information about possible birth defects. All pregnant UCSF patients undergo a comprehensive ultrasound exam before any invasive tests are performed. We will explain your ultrasound results at the time of your visit.

In some patients, an ultrasound raises concern for a fetal abnormality. This possibility makes ultrasound expertise crucial, so you may find it reassuring that we have extensive experience in performing and interpreting ultrasound exams in pregnancy.

The meaning of a positive result

If you receive positive results on a screening test, we recommend that you discuss its implications and your options with your doctor and a genetic counselor. They will explain what types of diagnostic testing are available. Whether to have invasive genetic testing is your decision.

If a diagnostic test finds a genetic abnormality, we recommend discussing the significance of the result with experts on the condition, including a medical geneticist and a genetic counselor, as well as your doctor.

Prenatal Cell-Free DNA Screening: MedlinePlus Medical Test

What is a prenatal cell-free DNA (cfDNA) screening?

Prenatal cell-free DNA (cfDNA) screening is a blood test for pregnant women. During pregnancy, some of an unborn baby's DNA circulates in the mother's bloodstream. A cfDNA screening checks this DNA to find out if the baby is more likely to have Down syndrome or another disorder caused by a trisomy.

A trisomy is a disorder of the chromosomes. Chromosomes are the parts of your cells that contain your genes. Genes are parts of DNA passed down from your mother and father. They carry information that determines your unique traits, such as height and eye color.

People normally have 46 chromosomes, divided into 23 pairs, in each cell.
If one of these pairs has an extra copy of a chromosome, it's called a trisomy. A trisomy causes changes in the way the body and brain develop.
In Down syndrome, there is an extra copy of chromosome 21. This is also known as trisomy 21. Down syndrome is the most common chromosome disorder in the United States.
Other trisomy disorders include Edwards syndrome (trisomy 18), where there is an extra copy of chromosome 18, and Patau syndrome (trisomy 13), where there is an extra copy of chromosome 13. These disorders are rare but more serious than Down syndrome. Most babies with trisomy 18 or trisomy 13 die within the first year of life.

A cfDNA screening has very little risk to you and your baby, but it can't tell you for sure whether your baby has a chromosome disorder. Your health care provider will need to order other tests to confirm or rule out a diagnosis.

Other names: cell-free fetal DNA, cffDNA, non-invasive prenatal test, NIPT

What is used for?

A cfDNA screening is most often used to show if your unborn baby has an increased risk for one of the following chromosome disorders:

Down syndrome (trisomy 21)
Edwards syndrome (trisomy 18)
Patau syndrome (trisomy 13)

The screening may also be used to:

Determine a baby's gender (sex). This may be done if an ultrasound shows that a baby's genitals are not clearly male or female. This may be caused by a disorder of the sex chromosomes.
Check Rh blood type. Rh is a protein found on red blood cells. If you have the protein, you are considered Rh positive. If you don't, you are Rh negative. If you are Rh negative and your unborn baby is Rh positive, your body's immune system may attack your baby's blood cells. If you find out you are Rh negative early in pregnancy, you can take medicines to protect your baby from dangerous complications.

A cfDNA screening can be done as early as the 10th week of pregnancy.

Why do I need a prenatal cfDNA screening?

Many health care providers recommend this screening to pregnant women who are at higher risk of having a baby with a chromosome disorder. You may be at higher risk if:

You are age 35 or older. A mother's age is the primary risk factor for having a baby with Down syndrome or other trisomy disorders. The risk increases as a woman gets older.
You've had another baby with a chromosome disorder.
Your fetal ultrasound didn't look normal.
Other prenatal test results were not normal.

Some health care providers recommend screening to all pregnant women. This is because the screening has almost no risk and has a high rate of accuracy compared with other prenatal screening tests.

You and your health care provider should discuss if a cfDNA screening is right for you.

What happens during a prenatal cfDNA screening?

A health care professional will take a blood sample from a vein in your arm, using a small needle. After the needle is inserted, a small amount of blood will be collected into a test tube or vial. You may feel a little sting when the needle goes in or out. This usually takes less than five minutes.

Will I need to do anything to prepare for this test?

You may want to speak to a genetic counselor before you get tested. A genetic counselor is a specially trained professional in genetics and genetic testing. He or she can explain the possible results and what they might mean to you and your baby.

Are there any risks to the test?

There is no risk to your unborn baby and very little risk to you. You may have slight pain or bruising at the spot where the needle was put in, but most symptoms go away quickly.

What do the results mean?

If your results were negative, it's unlikely that your baby has Down syndrome or another trisomy disorder. If your results were positive, it means there is an increased risk that your baby has one of these disorders. But it can't tell you for sure if your baby is affected. For a more confirmed diagnosis you'll need other tests, such as amniocentesis and chorionic villus sampling (CVS). These tests are usually very safe procedures, but they do have a slight risk of causing a miscarriage.

If you have questions about your results, talk to your health care provider and/or a genetic counselor.

Learn more about laboratory tests, reference ranges, and understanding results.

Is there anything else I need to know about a prenatal cfDNA screening?

cfDNA screenings are not as accurate in women who are pregnant with more than one baby (twins, triplets, or more).

References

ACOG: The American Congress of Obstetricians and Gynecologists [Internet]. Washington D.C.: American Congress of Obstetricians and Gynecologists; c2021. Cell-Free Prenatal DNA Screening Test; [cited 2021 Aug 5]; [about 3 screens]. Available from: https://www.acog.org/womens-health/infographics/cell-free-dna-prenatal-screening-test
ACOG: The American Congress of Obstetricians and Gynecologists [Internet]. Washington D.C.: American Congress of Obstetricians and Gynecologists; c2019. The Rh Factor: How It Can Affect Your Pregnancy; 2018 Feb [cited 2019 Nov 1]; [about 3 screens]. Available from: https://www.acog.org/Patients/FAQs/The-Rh-Factor-How-It-Can-Affect-Your-Pregnancy#what
Centers for Disease Control and Prevention [Internet]. Atlanta: U.S. Department of Health and Human Services; Genetic Counseling; [cited 2019 Nov 1]; [about 2 screens]. Available from: https://www.cdc.gov/genomics/gtesting/genetic_counseling.htm
Hartford HealthCare: The Hospital of Central Connecticut [Internet]. Hartford HealthCare; c2021. Genetics: Topic Overview; [cited 2021 Aug 5]; [about 3 screens]. Available from: https://thocc.org/health-community/health-resources/health-library/detail?id=tv7695
Lab Tests Online [Internet]. Seattle: Lab Tests Online; c2021. Cell-Free Fetal DNA; [cited 2021 Aug 5]; [about 4 screens]. Available from: https://www.merckmanuals.com/-/media/Manual/LabTests/CellFreeFetalDNA.html
March of Dimes [Internet]. Arlington (VA): March of Dimes; c2019. Down Syndrome; [cited 2019 Nov 1]; [about 3 screens]. Available from: https://www.marchofdimes.org/complications/down-syndrome.aspx
March of Dimes [Internet]. Arlington (VA): March of Dimes; c2019. Prenatal Tests; [cited 2019 Nov 1]; [about 3 screens]. Available from: https://www.marchofdimes.org/pregnancy/prenatal-tests.aspx
Mayo Clinic [Internet]. Mayo Foundation for Medical Education and Research; c1998–2019. Prenatal cell-free DNA screening: Overview; 2018 Sep 27 [cited 2019 Nov 1]; [about 3 screens]. Available from: https://www.mayoclinic.org/tests-procedures/noninvasive-prenatal-testing/about/pac-20384574
Merck Manual Consumer Version [Internet]. Kenilworth (NJ): Merck & Co. Inc.; c2019. Prenatal Diagnostic Testing; [updated 2017 Jun; cited 2019 Nov 1]; [about 3 screens]. Available from: https://www.merckmanuals.com/home/women-s-health-issues/detection-of-genetic-disorders/prenatal-diagnostic-testing
National Down Syndrome Society [Internet].Washington D.C.: National Down Syndrome Society; c2021. Understanding a Diagnosis of Down Syndrome; [cited 2021 Aug 5]; [about 2 screens]. Available from: https://www.ndss.org/lifespan/understanding-a-diagnosis-of-down-syndrome/
National Heart, Lung, and Blood Institute [Internet]. Bethesda (MD): U.S. Department of Health and Human Services; Blood Tests; [cited 2019 Nov 1]; [about 3 screens]. Available from: https://www.nhlbi.nih.gov/health-topics/blood-tests
National Society of Genetic Counselors [Internet]. Chicago: National Society of Genetic Counselors; Reasons to see a genetic counselor; [cited 2021 Aug 5]; [about 4 screens]. Available from: https://www.aboutgeneticcounselors.org/Reasons-to-See-a-Genetic-Counselor/Pregnancy-and-Family-Planning
Rafi I, Chitty L. Cell-free fetal DNA and non-invasive prenatal diagnosis. Br J Gen Pract. [Internet]. 2009 May 1 [cited 2019 Nov 1]; 59(562):e146–8. Available from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2673181
University of Rochester Medical Center [Internet]. Rochester (NY): University of Rochester Medical Center; c2019. Health Encyclopedia: First Trimester Screening; [cited 2019 Nov 1]; [about 2 screens]. Available from: https://www.urmc.rochester.edu/encyclopedia/content.aspx?contenttypeid=90&contentid=P08568
University of Rochester Medical Center [Internet]. Rochester (NY): University of Rochester Medical Center; c2019. Health Encyclopedia: Trisomy 13 and Trisomy 18 in Children; [cited 2019 Nov 1]; [about 2 screens]. Available from: https://www.urmc.rochester.edu/encyclopedia/content.aspx?contenttypeid=90&contentid=P02419

Down syndrome will be detected in the womb

INVITRO
Library
Useful articles
Down syndrome will be detected ...

2287 24 April

IMPORTANT!

The information in this section should not be used for self-diagnosis or self-treatment. In case of pain or other exacerbation of the disease, only the attending physician should prescribe diagnostic tests. For diagnosis and proper treatment, you should contact your doctor. nine0017 For a correct assessment of the results of your analyzes in dynamics, it is preferable to do studies in the same laboratory, since different laboratories may use different research methods and units of measurement to perform the same analyzes.

The manufacturer of kits for genetic analysis "Sequenom Inc" has begun to release a prenatal test for the diagnosis of Down syndrome.

The MaterniT21 test is based on the sequencing of DNA circulating in maternal plasma. It detects DNA fragments belonging to chromosome 21. As a rule, chromosome 21 in the blood of a pregnant woman accounts for 1.35% of the total amount of maternal and fetal DNA. An excess amount of material on chromosome 21 indicates a genetic anomaly, namely trisomy on chromosome 21, which is a characteristic feature of Down syndrome. nine0013

Trisomy 21 means the presence of many pathological psychological and physical characteristics. In most cases, people with Down syndrome have intellectual disabilities, although in many cases they are not so significant. As a rule, this is slow speech, impaired motor skills. And outwardly they look a little different: they are characterized by rounded flat faces.

Down syndrome is often accompanied by congenital heart disease, hearing or vision problems, and thyroid dysfunction. The average life expectancy for people with Down syndrome is 55 years. nine0013

The difference between MaterniT21 and other previously available tests is that it is much more accurate and can also be used as early as the tenth week of pregnancy. And this will enable future parents to make the only right decision for them: whether to leave a child with Down syndrome, realizing all the possible consequences, or to terminate an unwanted pregnancy.

The company claims that the test has an accuracy of 9 in clinical studies published in Genetics in Medicine.9.1%. The test study evaluated blood samples from 212 women with pregnancies with a baby with Down syndrome and 1,484 blood samples from women pregnant with a baby without Down syndrome. The test identified 209 out of 212 Down syndrome children (98.6% accuracy), with a total of three false positives (0.2%) and three false negatives.

According to thestar.com

IMPORTANT!

Recommendations

Alexis Carrel, 1912 Prize

eighteen January 12
nine0004
Emil Adolf von Behring, 1901 Prize

33 11 January
Albrecht Kossel, Nobel Prize 1910

42 December 29th

Cancer of the stomach and intestines will be detected by blood tests

Blood tests can replace endoscopy in the search for malignant neoplasms of the stomach and intestines

Human blood became the basis for the retina of the eye

The picture on the right is nothing but a fragment of the human retina. This photo is unique, however, not in that it was possible to capture such a fine structure. Another thing is surprising in it: this element was grown artificially. And this was succeeded by specialists from the University of Wisconsin and the American company Cellular Dynamics International. nine0013

Reality on the brink of fantasy

These operations were depicted on cobblestones and altar frescoes, described in detail in science fiction novels and filmed with invariable success. But the surgeons also "did not let us down": the most daring assumptions of science fiction writers only 100 years after the first experiments on transplanting vital organs in humans become a reality.

More nine0013

"Cat's whiskers" will save you from allergies. And the "cat's whiskers" will help in this. Of course, no one is going to shave our pets and make a miracle cure from their whiskers. The authors of the study used the expression "cat's whiskers" in a figurative sense - "a method of fine tuning." His scientists managed to develop after they figured out the molecular mechanism of the occurrence of an allergic reaction to cats - the most allergenic pets. In 40% of asthmatics, their disease is seriously aggravated if a cat runs nearby. nine0013

3D heart

Scientists have created an artificial heart using a 3D printer, using the world's first computerized tomography and transesophageal echocardiography technologies.

Down Syndrome - Symptoms, Risks, Early Diagnosis

Down Syndrome is a genetic disorder caused by abnormal cell division that results in an extra full or partial copy of chromosome 21. This extra genetic material causes developmental changes and physical features of the syndrome Down. nine0013

The manifestations of the syndrome vary in severity from person to person, causing lifelong mental retardation and developmental delay. This is the most common genetic chromosomal disorder and is the cause of limited learning ability in children. It also often causes other medical problems, including heart and gastrointestinal problems.

Unfortunately, a large number of stereotypes and misconceptions about this condition are still widespread in Russia. In addition, not all future parents know what to do in order to identify the risks of this syndrome. nine0013

In this article we will describe the main facts about Down syndrome and talk about the possibilities of modern genetic diagnostics, which allow us to detect this syndrome in time.

Down syndrome is one of the most common chromosomal abnormalities. Most of the manifestations of this condition are associated with trisomy - the presence of an additional complete or partial copy - of chromosome 21. This anomaly accounts for up to 90% of cases of Down syndrome.

Interesting fact

Why chromosome 21 has exactly this serial number

In 1959, when the first conference on the creation of the International System of Human Cytogenetic Nomenclature (ISCN) was held, scientists decided to number the non-sex chromosomes from 1 to 22 in accordance with their decreasing size. So, the smallest chromosome was numbered 22, and the largest - 1. However, at that time, geneticists did not yet have reliable tools for accurately assessing the size of each chromosome, and later it turned out that the 21st chromosome was still smaller than the 22nd. However, several studies have already been published linking the onset of Down syndrome to trisomy 21. To avoid confusion, the numbering was not changed. So chromosome 21 retained its number despite being the smallest. nine0013

Source: Thomas Eggermann and Gesa Schwanitz 2011

The cause of trisomy 21 has not yet been clearly identified. It is generally accepted that it is the result of a spontaneous error, which manifests itself in the inability of the 21st chromosome to separate during the development of an egg or sperm.

Source: National Human Genome Research Institute

In addition to the standard trisomy of chromosome 21, Down syndrome can be caused by its various chromosomal rearrangements: Robertsonian translocations, reciprocal translocations, duplications, submicroscopic aberrations. In rare cases of Down syndrome, mosaicism or mutation of chromosome 21 has been identified. The rarest case of Down syndrome is chromosome 21 tetrasomy - the presence of four free chromosomes 21, or two normal chromosomes and, in addition, isochromosome 21. Aberration usually leads to death in early pregnancy. nine0013

Learn more about the genetics of Down syndrome

Our geneticists have extensive experience in advising on congenital genetic diseases, including Down syndrome. You can sign up for a consultation and get answers to all questions about the genetic causes of this disease, as well as assess the risk of its occurrence in your future children. You can sign up by phone 8 (499) 677-52-22 or via chat.

Enroll

Down syndrome - symptoms

In addition to the well-known features of the disease, such as mental retardation and learning difficulties, Down syndrome has more than 80 other phenotypic manifestations, including those that affect the central nervous system, heart, gastrointestinal tract, skeleton, and immune system. The phenotypes associated with Down syndrome vary in both frequency and severity, resulting in a wide range of phenotypic combinations.

Cognitive impairment, hypotension, and craniofacial features are universal phenotypes, while cardiac anomalies affect only about half of people with Down syndrome. Individual phenotypes similar to those seen in Down syndrome have been documented in individuals without trisomy 21, but the overall higher frequency and severity of these phenotypes in individuals with Down syndrome suggests that trisomy plays an important role in initiating or modifying these features. Although it has been suggested that common mechanisms may be involved in the similar phenotypes seen in people with and without trisomy 21, the overall pathophysiology must be proven for each individual phenotype. nine0013

Source: Roper and Reeves, 2006

People with Down syndrome are at increased risk of congenital heart disease, epilepsy, leukemia, thyroid disease, and various mental disorders. Due to various physiological manifestations of the syndrome, such as growth retardation, low muscle tone, flexible ligaments, short arms, atlantoaxial joint instability, and others, their quality of life is markedly reduced. Most often, they cannot have children, or their children inherit the syndrome. nine0013

15 times more often

Leukemia occurs in children with Down syndrome.

Down syndrome - how to assess the risk?

Down syndrome occurs in about 1 in 660 newborns. At the same time, the risk of giving birth to a child with this syndrome increases with the age of the mother. In 20-year-old mothers, it is less than 0.1% and increases gradually to 3% in mothers aged 45.

0.5% of newborns

On average, this is the incidence of Down syndrome in developed countries. However, it should be noted that this risk increases with the age of the mother. nine0013

The age of the mother remains the only factor by which we can assess the risk of having Down syndrome before conception. Parents of children with this condition are usually healthy, and no behavioral or environmental factors affect the likelihood of having a child with this syndrome.

Various prenatal tests and comprehensive studies are used to assess the risk of Down syndrome after conception. non-invasive prenatal tests remain the safest and most reliable way

Benefits of NIPT

Safe
Informative
Fast
Exactly

The non-invasive prenatal test requires only the pregnant woman's venous blood, which contains small fragments of her own genetic material and fragments of the extracellular fetal DNA of the unborn child. With the help of a unique technology, extracellular fetal DNA is isolated, followed by its sequencing by the NGS method. Thanks to this, we can accurately assess the risks of Down syndrome in the fetus. nine0013

The choice of a non-invasive prenatal test depends on many factors. The main things we pay attention to are the history, the gestational age, whether the pregnancy occurred naturally or after IVF, whether donor cells were used in the IVF cycle, the number of fetuses, the presence of a missing twin, what are the results of other tests, and so on.

Want to choose NIPT?

Our geneticist will review the circumstances of your pregnancy and help you select a non-invasive prenatal test to assess your risk of Down syndrome. We have been doing this for over 8 years and have done thousands of consultations and tens of thousands of studies. nine0013

The possibilities of prenatal diagnosis are much broader than the assessment of the risk of Down syndrome. Modern medical technologies allow the use of a wide range of tools for risk assessment and diagnosis of chromosomal rearrangements, mutations and hereditary diseases.