How to know if your baby will have down syndrome
Screening for Down syndrome | Pregnancy Birth and Baby
Screening for Down syndrome | Pregnancy Birth and Baby beginning of content5-minute read
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If you or someone you care about has a child with Down syndrome, or is pregnant with a Down syndrome baby, you may have many questions or feel overwhelmed by what this means. The most important thing that babies with Down syndrome need — just like any baby — is a loving, secure environment in which they feel nurtured and supported.
What is Down syndrome?
Down syndrome is the most common chromosomal condition that a baby can be born with. Around 1 in every 1,000 babies born in Australia has Down syndrome.
Down syndrome is also known as Trisomy 21. People with Down syndrome usually look different from other people and may have some difficulty learning new things.
What causes Down syndrome?
Normally, every cell in the human body — except egg and sperm cells — has 46 chromosomes. The egg and sperm cells normally have 23 chromosomes each.
The most common cause of Down syndrome is when an extra copy of chromosome 21 randomly appears in either the egg or sperm. At conception, when the egg and sperm meet, the extra copy of chromosome 21 grows throughout all of the embryo’s cells, giving them each 47 chromosomes instead of the usual 46.
Less commonly, the extra copy of the chromosome can appear in some of the embryo’s cells after conception. This is called mosaicism and results in some cells having 46 chromosomes and some having 47.
Another rare form of the syndrome is caused by ‘Robertsonian translocation’. This occurs when a piece of chromosome 21 breaks off and becomes joined to another chromosome before or after conception. In this case, the embryo’s cells will all have 46 chromosomes, but each cell still contains an extra copy of chromosome 21.
What are the most common features of Down syndrome?
Many babies with Down syndrome have one or more of the following features at birth:
- low muscle tone ('floppy' muscles)
- a flatter face with eyes slanting upward
- small ears and a wider neck than usual
- a single crease across the palm of the hand
- a gap between the first and second toes
Down syndrome is also associated with intellectual disability.
However, not everyone with Down syndrome will have all of these features.
What medical complications might come with Down syndrome?
About 1 in every 2 babies born with Down syndrome will have heart problems and approximately 1 in 10 will have gastrointestinal (gut) problems. Hearing and vision problems are also more common in people with Down syndrome.
How is Down syndrome diagnosed?
Pregnant women are offered routine antenatal tests at different times during pregnancy and for different reasons. These include screening tests, such as ultrasounds and blood tests, that can help estimate your baby’s risk of being born with a range of conditions, including Down syndrome.
Non-invasive prenatal testing (NIPT) is a new blood test that can be done as an alternative screening test.
Diagnostic tests (such as chorionic villus sampling or amniocentesis) will show whether a baby actually has Down syndrome.
After the baby is born, chromosome testing from a blood sample, may be done to confirm Down syndrome.
What is the treatment for Down syndrome?
There is currently no way to prevent or cure Down syndrome. Prenatal testing allows you and your family to make informed decisions, including ending the pregnancy. For this reason, before you have the test it’s a good idea to think about why you are choosing to do it, and how you will feel once you get the results.
Consider also who you want to discuss any important decisions with — your partner, a friend or family member, or a health professional such as your doctor or midwife are all good options.
Early diagnosis can also help you and your doctor continue to check your baby for complications and to act early if needed. Some people with Down syndrome may need surgery to repair heart defects or gut blockages. Medicines to treat thyroid disease may also be needed in some cases.
Children all learn and develop at their own pace. However, there are effective early intervention programs for children with Down syndrome that can help them reach their learning potential.
Resources and support
Down Syndrome Australia provides support, information and resources for people with Down syndrome and their families across Australia.
Support services include:
- information and advice about Down syndrome
- information about local support groups
- home visits
- new parent packs
- workshops and webinars
- online support groups for you and your family
A national phone number (1300 881 935) can connect you with your local state or territory Down syndrome organisation for further information.
Speak to a maternal child health nurse
Call Pregnancy, Birth and Baby to speak to a maternal child health nurse on 1800 882 436 or video call. Available 7am to midnight (AET), 7 days a week.
Sources:
Centre for Genetics education (Trisomy 32 - Down Syndrome), Lab Tests Online (Down syndrome), Down Syndrome Australia (Prenatal and New Parent)Learn more here about the development and quality assurance of healthdirect content.
Last reviewed: March 2022
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Related pages
- Caring for a child with Down syndrome
- What is Down syndrome?
- Questions to ask your doctor about tests and scans
- Routine antenatal tests
- Pregnancy checkups, screenings and scans
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Non-invasive prenatal testing (NIPT)
A non-invasive prenatal test (NIPT) is a sensitive test to screen for Down syndrome and some other chromosomal disorders in the first trimester of pregnancy.
Read more on Pregnancy, Birth & Baby website
What is Down syndrome?
Down syndrome is a genetic disorder characterised by mental and developmental impairments.
Read more on Pregnancy, Birth & Baby website
What is Down syndrome? – Down Syndrome Australia
Down syndrome is a genetic condition and is also sometimes known as trisomy 21. You can find out more about Down syndrome below. You can also turn on the Easy Read for this page.
Read more on Down Syndrome Australia website
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Facts about Down Syndrome | CDC
What is Down Syndrome?
Down syndrome is a condition in which a person has an extra chromosome. Chromosomes are small “packages” of genes in the body. They determine how a baby’s body forms and functions as it grows during pregnancy and after birth. Typically, a baby is born with 46 chromosomes. Babies with Down syndrome have an extra copy of one of these chromosomes, chromosome 21. A medical term for having an extra copy of a chromosome is ‘trisomy.’ Down syndrome is also referred to as Trisomy 21. This extra copy changes how the baby’s body and brain develop, which can cause both mental and physical challenges for the baby.
Even though people with Down syndrome might act and look similar, each person has different abilities. People with Down syndrome usually have an IQ (a measure of intelligence) in the mildly-to-moderately low range and are slower to speak than other children.
Some common physical features of Down syndrome include:
- A flattened face, especially the bridge of the nose
- Almond-shaped eyes that slant up
- A short neck
- Small ears
- A tongue that tends to stick out of the mouth
- Tiny white spots on the iris (colored part) of the eye
- Small hands and feet
- A single line across the palm of the hand (palmar crease)
- Small pinky fingers that sometimes curve toward the thumb
- Poor muscle tone or loose joints
- Shorter in height as children and adults
How Many Babies are Born with Down Syndrome?
Down syndrome remains the most common chromosomal condition diagnosed in the United States. Each year, about 6,000 babies born in the United States have Down syndrome. This means that Down syndrome occurs in about 1 in every 700 babies.1
Types of Down Syndrome
There are three types of Down syndrome. People often can’t tell the difference between each type without looking at the chromosomes because the physical features and behaviors are similar.
- Trisomy 21: About 95% of people with Down syndrome have Trisomy 21.2 With this type of Down syndrome, each cell in the body has 3 separate copies of chromosome 21 instead of the usual 2 copies.
- Translocation Down syndrome: This type accounts for a small percentage of people with Down syndrome (about 3%).2 This occurs when an extra part or a whole extra chromosome 21 is present, but it is attached or “trans-located” to a different chromosome rather than being a separate chromosome 21.
- Mosaic Down syndrome: This type affects about 2% of the people with Down syndrome. 2 Mosaic means mixture or combination. For children with mosaic Down syndrome, some of their cells have 3 copies of chromosome 21, but other cells have the typical two copies of chromosome 21. Children with mosaic Down syndrome may have the same features as other children with Down syndrome. However, they may have fewer features of the condition due to the presence of some (or many) cells with a typical number of chromosomes.
Causes and Risk Factors
- The extra chromosome 21 leads to the physical features and developmental challenges that can occur among people with Down syndrome. Researchers know that Down syndrome is caused by an extra chromosome, but no one knows for sure why Down syndrome occurs or how many different factors play a role.
- One factor that increases the risk for having a baby with Down syndrome is the mother’s age. Women who are 35 years or older when they become pregnant are more likely to have a pregnancy affected by Down syndrome than women who become pregnant at a younger age. 3-5However, the majority of babies with Down syndrome are born to mothers less than 35 years old, because there are many more births among younger women.6,7
Diagnosis
There are two basic types of tests available to detect Down syndrome during pregnancy: screening tests and diagnostic tests. A screening test can tell a woman and her healthcare provider whether her pregnancy has a lower or higher chance of having Down syndrome. Screening tests do not provide an absolute diagnosis, but they are safer for the mother and the developing baby. Diagnostic tests can typically detect whether or not a baby will have Down syndrome, but they can be more risky for the mother and developing baby. Neither screening nor diagnostic tests can predict the full impact of Down syndrome on a baby; no one can predict this.
Screening Tests
Screening tests often include a combination of a blood test, which measures the amount of various substances in the mother’s blood (e. g., MS-AFP, Triple Screen, Quad-screen), and an ultrasound, which creates a picture of the baby. During an ultrasound, one of the things the technician looks at is the fluid behind the baby’s neck. Extra fluid in this region could indicate a genetic problem. These screening tests can help determine the baby’s risk of Down syndrome. Rarely, screening tests can give an abnormal result even when there is nothing wrong with the baby. Sometimes, the test results are normal and yet they miss a problem that does exist.
Diagnostic Tests
Diagnostic tests are usually performed after a positive screening test in order to confirm a Down syndrome diagnosis. Types of diagnostic tests include:
- Chorionic villus sampling (CVS)—examines material from the placenta
- Amniocentesis—examines the amniotic fluid (the fluid from the sac surrounding the baby)
- Percutaneous umbilical blood sampling (PUBS)—examines blood from the umbilical cord
These tests look for changes in the chromosomes that would indicate a Down syndrome diagnosis.
Other Health Problems
Many people with Down syndrome have the common facial features and no other major birth defects. However, some people with Down syndrome might have one or more major birth defects or other medical problems. Some of the more common health problems among children with Down syndrome are listed below.8
- Hearing loss
- Obstructive sleep apnea, which is a condition where the person’s breathing temporarily stops while asleep
- Ear infections
- Eye diseases
- Heart defects present at birth
Health care providers routinely monitor children with Down syndrome for these conditions.
Treatments
Down syndrome is a lifelong condition. Services early in life will often help babies and children with Down syndrome to improve their physical and intellectual abilities. Most of these services focus on helping children with Down syndrome develop to their full potential. These services include speech, occupational, and physical therapy, and they are typically offered through early intervention programs in each state. Children with Down syndrome may also need extra help or attention in school, although many children are included in regular classes.
Other Resources
The views of these organizations are their own and do not reflect the official position of CDC.
- Down Syndrome Research Foundation (DSRF)
DSRF initiates research studies to better understand the learning styles of those with Down syndrome. - Global Down Syndrome Foundation
This foundation is dedicated to significantly improving the lives of people with Down syndrome through research, medical care, education and advocacy. - National Association for Down Syndrome
The National Association for Down Syndrome supports all persons with Down syndrome in achieving their full potential. They seek to help families, educate the public, address social issues and challenges, and facilitate active participation. - National Down Syndrome Society (NDSS)
NDSS seeks to increase awareness and acceptance of those with Down syndrome.
References
- Mai CT, Isenburg JL, Canfield MA, Meyer RE, Correa A, Alverson CJ, Lupo PJ, Riehle‐Colarusso T, Cho SJ, Aggarwal D, Kirby RS. National population‐based estimates for major birth defects, 2010–2014. Birth Defects Research. 2019; 111(18): 1420-1435.
- Shin M, Siffel C, Correa A. Survival of children with mosaic Down syndrome. Am J Med Genet A. 2010;152A:800-1.
- Allen EG, Freeman SB, Druschel C, et al. Maternal age and risk for trisomy 21 assessed by the origin of chromosome nondisjunction: a report from the Atlanta and National Down Syndrome Projects. Hum Genet. 2009 Feb;125(1):41-52.
- Ghosh S, Feingold E, Dey SK. Etiology of Down syndrome: Evidence for consistent association among altered meiotic recombination, nondisjunction, and maternal age across populations. Am J Med Genet A. 2009 Jul;149A(7):1415-20.
- Sherman SL, Allen EG, Bean LH, Freeman SB. Epidemiology of Down syndrome. Ment Retard Dev Disabil Res Rev. 2007;13(3):221-7.
- Adams MM, Erickson JD, Layde PM, Oakley GP. Down’s syndrome. Recent trends in the United States. JAMA. 1981 Aug 14;246(7):758-60.
- Olsen CL, Cross PK, Gensburg LJ, Hughes JP. The effects of prenatal diagnosis, population ageing, and changing fertility rates on the live birth prevalence of Down syndrome in New York State, 1983-1992. Prenat Diagn. 1996 Nov;16(11):991-1002.
- Bull MJ, the Committee on Genetics. Health supervision for children with Down syndrome. Pediatrics. 2011;128:393-406.
Screening tests for Down syndrome in the first 24 weeks of pregnancy
Relevance
Down syndrome (also known as Down syndrome or Trisomy 21) is an incurable genetic disorder that causes significant physical and mental health problems and disability. However, there is great variation in how Trisomy Down affects people. Some individuals have severe suffering, while others have little problems and are able to lead relatively normal lives. There is no way to predict how badly each child may be affected.
Parents-to-be are given the option of having a Down test during pregnancy to help them make decisions. If a pregnant woman is carrying a child with Down syndrome, then a decision must be made whether to terminate or continue the pregnancy. This information offers parents the opportunity to plan for life with a Down child.
The most accurate tests to detect Down include testing of amniotic fluid (fluid around the fetus, amniocentesis required) or placental tissue (chorionic villus biopsy (CVS)) for abnormal chromosomes associated with Down. Both tests require the insertion of a needle into the mother's abdomen and increase the risk of miscarriage. Thus, the tests are not suitable to be given to all pregnant women. Instead, screening uses tests that measure markers in the mother's blood, urine, or baby's ultrasound. These screening tests are not perfect, they can miss cases of Down and also give a "high risk" result to some women whose children do not have Down. Thus, pregnancies identified as Down's "high risk" pregnancies using these screening tests require further testing by amniocentesis or CVS to confirm a Down's diagnosis.
What we did
The aim of this review was to find out which of the screening tests done during the first 24 weeks of pregnancy are most accurate in predicting the risk of Down pregnancy. We studied 7 different urinary markers that can be used alone, in ratios, or in combination, taken up to 24 weeks of gestation. This cumulatively creates 24 screening tests for Down. We found 19 studies involving 18,013 pregnant women, of which 527 were pregnancies with Down syndrome.
What we found
Evidence does not support the use of urine tests to screen for Down syndrome during the first 24 weeks of pregnancy. The amount of evidence is limited. These tests are not offered in routine clinical practice.
Other important information to consider
Urine testing itself has no side effects for the woman. However, some women who have a "high-risk" screening test result and who are undergoing amniocentesis or CVS are at risk of having a non-Down's syndrome non-parous baby (healthy miscarriage). Parents will need to weigh this risk when deciding whether or not to have an amniocentesis or CVS after receiving a "high risk" screening test result.
Translation notes:
Translation: Kong Hong Han. Editing: Ziganshina Lilia Evgenievna. Project coordination for translation into Russian: Cochrane Russia - Cochrane Russia (branch of the Northern Cochrane Center on the basis of Kazan Federal University). For questions regarding this transfer, please contact us at: [email protected]
Screening tests for Down syndrome in the first 24 weeks of pregnancy
Relevance
Down's syndrome (also known as Down's disease or Trisomy 21) is an incurable genetic disorder that causes significant physical and mental health problems and disability. However, Down syndrome affects people in completely different ways. Some have significant symptoms, while others have minor health problems and are able to lead relatively normal lives. There is no way to predict how badly a child might be affected.
Expectant parents during pregnancy are given the opportunity to have a screening test for Down syndrome in their baby to help them make a decision. If a mother is carrying a child with Down syndrome, then a decision should be made whether to terminate the pregnancy or keep it. The information gives parents the opportunity to plan life with a child with Down syndrome.
The most accurate screening tests for Down syndrome include amniotic fluid (amniocentesis) or placental tissue (chorionic villus biopsy (CVS)) to identify abnormal chromosomes associated with Down syndrome. Both of these tests involve inserting a needle into the mother's abdomen, which is known to increase the risk of miscarriage. Thus, screening tests are not suitable for all pregnant women. Therefore, more often take blood and urine tests of the mother, and also conduct an ultrasound examination of the child. These screening tests are not perfect because they can miss cases of Down syndrome and are also at high risk of being positive when the child does not have Down syndrome. Thus, if a high risk is identified using these screening tests, further amniocentesis or CVS is required to confirm the diagnosis of Down syndrome.
What we did
We analyzed combinations of serum screening tests in the first (up to 14 weeks) and second (up to 24 weeks) trimesters of pregnancy with or without ultrasound screening in the first trimester. Our goal was to identify the most accurate tests for predicting the risk of Down syndrome during pregnancy. One ultrasound index (neckfold thickness) and seven different serological indexes (PAPP-A, total hCG, free beta-hCG, unbound estriol, alpha-fetoprotein, inhibin A, ADAM 12) were studied, which can be used separately, in ratios or in combination with each other, obtained before 24 weeks of gestation, thereby obtaining 32 screening tests for the detection of Down's syndrome. We found 22 studies involving 228615 pregnant women (including 1067 fetuses with Down syndrome).
What we found
During Down Syndrome screening, which included tests during the first and second trimesters that combined to determine overall risk, we found that a test that included neckfold measurement and PAPP- A in the first trimester, as well as the determination of total hCG, unbound estriol, alpha-fetoprotein and inhibin A in the second trimester, turned out to be the most sensitive, as it allowed to determine 9out of 10 pregnancies associated with Down syndrome. Five percent of pregnant women who were determined to be at high risk on this combination of tests would not have a child with Down syndrome. There have been relatively few studies evaluating these tests, so we cannot draw firm conclusions or recommendations about which test is best.
Other important information to consider
Ultrasounds themselves have no adverse effects on women, and blood tests can cause discomfort, bruising, and, in rare cases, infection.