Down syndrome test after birth

How do health care providers diagnose Down syndrome?

Health care providers can check for Down syndrome during pregnancy or after a child is born. There are two types of tests for Down syndrome during pregnancy:

  • A prenatal screening test. This test can show an increased likelihood that a fetus has Down syndrome, but it cannot determine Down syndrome is definitely present. If a screening test shows an increased likelihood, a diagnostic test can be ordered.
  • A prenatal diagnostic test. This test can determine with certainty that Down syndrome is present. Diagnostic tests carry a slightly greater risk to the fetus than do screening tests.

The American Congress of Obstetricians and Gynecologists (ACOG) recommends that all pregnant women be offered a Down syndrome screening test.1

Prenatal Screening for Down Syndrome

There are several options for Down syndrome prenatal screening. These include:

  • A blood test and an ultrasound test during the first trimester of pregnancy. This is the most accepted approach for screening during the first trimester. A blood test enables a health care provider to check for “markers,” such as certain proteins, in the mother’s blood that suggest an increased likelihood of Down syndrome.2 Then the health care provider does an ultrasound test, which uses high-frequency sound waves to create images. An ultrasound can detect fluid at the back of a fetus’s neck, which sometimes indicates Down syndrome. The ultrasound test is called measurement of nuchal translucency. During the first trimester, this combined method results in more effective or comparable detection rates than methods used during the second trimester.3
  • A blood test during the second trimester of pregnancy. As in the first trimester, a blood test enables a health care provider to check for markers in the mother’s blood. A triple screen looks for levels of three different markers; a quadruple screen looks for levels of four different markers.3,4
  • A combined test (sometimes called an integrated test). This approach uses both a blood test and an ultrasound during the first trimester as well as a second-trimester blood test. Health care providers then combine all these results to produce one Down syndrome risk rating.2

If a woman is pregnant with twins or triplets, a blood test will not be as reliable because the substances from a Down syndrome fetus may be harder to detect.2,3

Prenatal Diagnostic Testing for Down Syndrome

If a screening test suggests the likelihood of Down syndrome, a diagnostic test can be performed. ACOG recommends that pregnant women of all ages be given the option of skipping the screening test and getting a diagnostic test first. Until recently, only women over age 35 and other at-risk women were offered this option because diagnostic tests carry a slight risk of miscarriage.1 Before having diagnostic testing, a pregnant woman and her family may want to meet with a genetic counselor to discuss their family history and the risks and benefits of testing in their specific situation.

Diagnostic testing for Down syndrome involves removing a sample of genetic material. After it is removed, the sample is checked for extra material from chromosome 21, which may indicate that a fetus has Down syndrome. Parents usually get the results of the test a week or two later. The following procedures are used to extract samples.

  • Amniocentesis (pronounced am-nee-oh-sen-TEE-sis). A health care provider takes a sample of amniotic (pronounced am-nee-OT-ik) fluid, which is then tested for the extra chromosome. This test cannot be done until week 14 to 18 of the pregnancy.
  • Chorionic villus (pronounced KOHR-ee-on-ik VIL-uhs) sampling (CVS). A health care provider takes a sample of cells from a part of the placenta (pronounced pluh-SEN-tuh), which is the organ that connects a woman and her fetus, and then tests the sample for the extra chromosome. This test is done between weeks 9 and 11 of pregnancy.
  • Percutaneous (pronounced pur-kyoo-TEY-nee-uhs) umbilical blood sampling (PUBS). A health care provider takes a sample of fetal blood in the umbilical cord through the uterus. The blood is then tested for the extra chromosome. PUBS is the most accurate diagnostic method and can confirm the results of CVS or amniocentesis. However, PUBS cannot be performed until later in the pregnancy, during the 18th to 22nd week.5

Prenatal diagnostic testing does involve some risk to the mother and fetus, including a slight risk of miscarriage.6,7,8,9 If you and your family are considering prenatal diagnostic testing for Down syndrome, discuss all the risks and benefits with your health care provider.

Chromosomal Testing of Maternal Blood

A pregnant woman who is at risk for having an infant with Down syndrome also can have a chromosomal test using her blood. A mother’s blood carries DNA from the fetus, which may show extra chromosome 21 material.3 A more invasive test then would usually confirm the blood test.

Testing and In Vitro Fertilization

Another approach to diagnosis is used in conjunction with in vitro fertilization. Preimplantation genetic diagnosis (PGD) allows clinicians to detect chromosome imbalances or other genetic conditions in a fertilized egg before it is implanted into the uterus.

This technique is useful mostly for couples who are at risk of passing on a variety of genetic conditions, including X-linked disorders, as well as couples who have suffered repeated spontaneous pregnancy losses, sub-fertile couples, or those at risk for single-gene disorders.

Those interested in PGD should have genetic counseling and should consider close monitoring and additional testing during their pregnancies, given some increased risk of chromosomal abnormalities arising secondary to the in vitro fertilization process.10

Diagnosis of Down Syndrome After Birth

A diagnosis of Down syndrome after birth is often based initially on physical signs of the syndrome.

But because individuals with Down syndrome may not have these symptoms, and because many of these symptoms are common in the general population, the health care provider will take a sample of the baby’s blood to confirm the diagnosis. The blood sample is analyzed to determine the number of the baby’s chromosomes.11

Caring for a Baby Who Has Down Syndrome

Down syndrome is a genetic condition. A person who has Down syndrome is born with an extra copy of the 21st chromosome. It’s detected at birth. It also can be detected during pregnancy with genetic testing. Down syndrome causes some physical and intellectual disabilities. Most of the time, it’s at a moderate level. If you have a baby with Down syndrome, you’ll need to care for, talk to, play with, and love him or her like any other infant.

Path to improved development

In many important ways, children who have Down syndrome are very much like other children. They have the same moods and emotions, they like to learn new things, play, and enjoy life. You can help your child develop by providing as many chances as possible for him or her to do these things. Read to your child and play with him or her, just as you would any other child. Help your child to have positive experiences with new people and places.

Every baby born with Down syndrome is different. As your new baby grows, you’ll need to pay special attention to his or her physical and intellectual development. Your baby also may have some health problems that require extra care. Not all babies born with Down syndrome have health problems. Not all babies will have the same health problems.

Physical health: Babies who are born with Down syndrome are more likely to have:

  • Feeding issues.Learning to breastfeed or suck a bottle may take your baby longer to learn. Breastfeeding is good for all babies, including babies who have Down syndrome. Your doctor, a nurse, a feeding therapist, or another mom who has a baby with Down syndrome can provide tips and special training.
  • Heart defects.Some heart problems will require surgery within the first year. Other problems will correct themselves over time. If your baby has a heart problem, your doctor will refer you to a cardiologist. He or she will monitor your baby’s heart health until the problem is corrected.
  • Hearing issues.Some babies will have partial hearing loss. Babies who have Down syndrome have smaller Eustachian tubes (part of your inner ear). This causes fluid buildup. That can be relieved with tubes. Your doctor will surgically insert the tubes to relieve the fluid. Some babies have permanent nerve damage. This can cause permanent hearing loss. Hearing aids often help your child hear. Without treatment, the hearing loss can affect your baby’s speech development.
  • Vision problems.This might include cataracts or other eye issues requiring glasses.

Less likely health issues include:

  • Intestinal blockage at birth requiring surgery.
  • Hip dislocation.
  • Thyroid disease.
  • This is when red blood cells can’t carry enough oxygen to the body.
  • Iron deficiency. This is anemia where the red blood cells don’t have enough iron.
  • Leukemia in infancy or early childhood.

Developmental milestones

Your baby will reach all the same infant and toddler milestones. However, it will take him or her a little longer. Early intervention academic support as well as physical and occupational therapy can help children who have Down syndrome develop. This covers the following topics:

The earlier your baby starts receiving therapy, the better he or she will develop and succeed in life.

Many cities have support groups and community resources to help parents who have children with Down syndrome. These resources also are helpful for siblings and other family members. Your doctor can tell you where to find these resources in your community.

Things to consider

In most cases, for every 100 couples who have another baby, 1 will have another baby with Down syndrome. If you’re planning on having more children, talk with your doctor. He or she can help you decide whether to seek genetic counseling before you become pregnant again.

When you first learn that your baby has Down syndrome, you may feel disappointment, grief, anger, frustration, fear, and anxiety about the future. These feelings are all normal. Talking to other parents of children who have Down syndrome can be helpful. They know how you’re feeling. You also can talk to your family doctor or visit a support group. These resources let you share your feelings and get additional information.

Questions to ask your doctor

  • Do babies who have Down syndrome have low muscle tone?
  • Will my baby learn to read?
  • Will my baby grow up to be independent?
  • How can I tell if I am sad about my baby’s diagnosis or if I’m suffering from post-partum depression?


Centers for Disease Control and Prevention: Down Syndrome

National Institutes of Health, MedlinePlus: Down Syndrome

How Doctors Detect Whether a Baby Will Be Born With Down Syndrome

In Some Cases Down Syndrome Is Diagnosed After Birth

A lot of expectant parents make the decision to skip Down syndrome screening and testing altogether.

“Many moms over 35 get prenatal testing to assess whether the fetus has the condition,” Pipan notes. “But younger moms often don’t.”

She says these parents have usually decided that it isn’t necessary or useful for them to know whether or not their child has Down syndrome ahead of delivering the baby.

Though in some cases knowing a baby will be born with Down syndrome can lead to additional prenatal testing and monitoring to help ensure a safe delivery, as many Down syndrome pregnancies are considered high risk.

If a developing fetus has Down syndrome and the condition is not diagnosed during pregnancy, it’s diagnosed at the time the baby is born. This diagnosis uses a combination of physical exams and a blood test.

During the physical exam, a doctor or nurse will check the baby for a lack of typical muscle tone, a single deep crease across the palm of the hand, a slightly flattened facial profile, and an upward slant to the eyes — all of which are indicative of Down syndrome. If these physical features are present, a blood test can determine if the baby has an extra full or partial chromosome 21. If the baby does have the extra chromosome, a doctor will make a Down syndrome diagnosis.

What a diagnosis of Down syndrome cannot offer expectant parents is firm predictions about their child’s future disabilities.

Learning difficulties, physical disabilities, and other challenges often emerge as a child ages, Heller explains. And there’s no way to know from a diagnostic test what those future disabilities will be. In some cases, challenges or health conditions may not surface until the child reaches adulthood.

But, Pipan adds, “It’s a reality that most people with Down syndrome are going to lead healthy and productive lives, and they’ll be contributing members to their families, their communities, and the workforce.”

Prenatal Testing for Down Syndrome

Screening Tests

Sequential Integrated Screening — Sequential integrated screening is offered to all pregnant women by the state of California. This non-invasive screening is performed in two steps.

In the first step, which is performed between 10 and 14 weeks of pregnancy, a blood sample is taken from the mother and a nuchal translucency ultrasound is performed to measure the amount of fluid at the back of the baby’s neck. If the blood test is scheduled prior to the ultrasound, we can provide the results at the end of the ultrasound appointment. The results of the blood test, the nuchal translucency measurement and the mother’s age are used to estimate the risk for Down syndrome and trisomy 18.

The second step is a maternal blood test between 15 to 20 weeks of pregnancy. 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, an open neural tube defect or an abdominal wall defect.

Diagnostic Tests

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

Amniocentesis — Amniocentesis is used most commonly to identify chromosomal problems such as Down syndrome. When the fetus is known to be at risk, it can detect other genetic diseases like cystic fibrosis, Tay-Sachs disease and sickle cell disease.

An amniocentesis procedure for genetic testing is typically performed between 15 and 20 weeks of pregnancy. Under ultrasound guidance, a needle is inserted through the abdomen to remove a small amount of amniotic fluid. The cells from the fluid are then cultured and a karyotype analysis — an analysis of the chromosomal make-up of the cells — is performed. It takes about two weeks to receive the results of the test.

Amniocentesis detects most chromosomal disorders, such as Down syndrome, with a high degree of accuracy. Testing for other genetic diseases, such as Tay-Sachs disease, is not routinely performed but can be detected through specialized testing if your fetus is known to be at risk. Testing for neural tube defects, such as spina bifida, also can be performed.

There is a small risk of miscarriage as a result of amniocentesis — about 1 in 100 or less. Miscarriage rates for procedures performed at UCSF Medical Center are less than 1 in 350.

Chorionic Villus Sampling (CVS) — Like amniocentesis, chorionic villus sampling is used most commonly to identify chromosomal problems such as Down syndrome. It can detect other genetic diseases like cystic fibrosis, Tay-Sachs disease and sickle cell disease in at-risk fetuses. The main advantage of CVS over amniocentesis is that it 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. Under ultrasound guidance, the tissue is obtained either with a needle inserted through the abdomen or a catheter inserted through the cervix. The tissue is then cultured and a karyotype analysis of the chromosomal make-up of the cells is performed. It takes about two weeks to receive the results.

The advantage of CVS over amniocentesis is that the test is performed much earlier in pregnancy, so results are typically available by the end of the third month. A disadvantage is that spinal cord defects cannot be detected. Expanded alpha fetoprotein (AFP) blood testing or ultrasound can be performed later in the pregnancy to screen for spinal cord defects.

There is a small risk of miscarriage as a result of CVS — 1 in 100 or less. Miscarriage rates for procedures performed at UCSF Medical Center are less than 1 in 350.

Ultrasound — The primary purpose of ultrasound is to determine the status of a pregnancy — the due date, size of the fetus and if the mother is carrying multiples. Ultrasound also can provide some information about possible birth defects in a fetus. All patients at UCSF Medical Center undergo a comprehensive ultrasound examination before any invasive tests are performed. Results of the ultrasound are explained at the time of the visit.

In some patients, an ultrasound raises concern of a possible abnormality in the fetus. We have extensive experience in performing and interpreting ultrasounds in pregnancy.

If You Receive a Positive Result

If you receive positive results on a screening test, we recommend that you discuss this with your doctor and a genetic counselor. Options for further diagnostic testing will be explained. The decision as to whether to have invasive genetic testing is up to you.

If a diagnostic test finds a genetic abnormality, the significance of such results should be discussed with experts familiar with the condition, including a medical geneticist and a genetic counselor, as well as your own doctor.

Down Syndrome | Diagnosis & Treatment

How is Down syndrome diagnosed?

Down syndrome can be detected during pregnancy through prenatal tests or diagnosed after birth with a chromosomal analysis called a karyotype.

Prenatal tests

Prenatal tests are optional tests that can be performed during pregnancy to identify a fetus’s sex, age, size and placement in the uterus. Prenatal tests also detect chromosomal conditions such as Down syndrome, congenital heart defects, and other genetic conditions.

Prenatal tests and timing

Ideally, the best time to start thinking about prenatal tests is before conception. Your doctor can look at your family’s medical history to see if the parents might have an increased risk for having a child with a genetic condition such as Down syndrome. Sometimes, the doctor will recommend pre-conception testing for parents articular conditions based on this evaluation.

Before any parent decides whether or not to get prenatal testing, it’s important to know all the options and the advantages and disadvantages of each one.

Screening tests

Screening tests determine the likelihood of Down syndrome and other medical conditions without providing a definite diagnosis.

The different types of screening tests include:

  • blood tests that measure protein and hormone levels in pregnant women. Abnormal levels, whether high or low, can indicate a genetic condition.
  • ultrasound, a non-invasive imagining technique that uses sound waves to generate an image of the fetus. An ultrasound can identify congenital heart conditions and other structural changes such as extra skin at the base of the neck that may indicate Down syndrome.

Clinicians use the combined results of blood tests and ultrasound results to estimate the chance that a fetus has Down syndrome.

Based on the results of the screening tests and the mother’s age, a clinician may recommend follow-up tests such as MaternaT21 or Panorama to look for fetal DNA in the maternal blood. These relatively new tests indicate if there is a high or low probability that a fetus has Down syndrome. These tests are not diagnostic and cannot say with absolute certainty whether or not a fetus has Down syndrome.

Diagnostic tests

Diagnostic tests can determine whether a fetus has Down syndrome with nearly 100 percent accuracy. However, because these tests require using a needle to obtain a sample from within the uterus, they carry a small increased risk of miscarriage and other complications.

Diagnostic test options include:

  • chorionic villus sampling (CVS), a prenatal diagnosis method in which a small biopsy of the placenta is taken for specific genetic testing. CVS is used to detect any condition that involves specific chromosomal abnormalities, like Down syndrome. This test is usually performed during the first trimester between 10-14 weeks of gestation.
  • amniocentesis, a prenatal diagnosis method in which a needle is inserted into the amniotic sac that surrounds the fetus. Amniocentesis is most often used to detect Down syndrome and other chromosomal abnormalities. This test is usually done in the second trimester, after 15 weeks of gestation.

Testing for related conditions

  • ultrasounds use sound waves to create an image of a fetus’ internal organs so clinicians can look for markers of Down syndrome and other possible issues like intestinal
  • echocardiograms use sound waves to create an image of the heart so doctors can look for signs of congenital heart defects
  • fetal magnetic resonance imaging (MRI) provides clinicians an image of a fetus’ internal organs, including the brain and intestines

Diagnostic testing after birth

Down syndrome can also be diagnosed after a baby is born. Clinicians can usually tell if a baby should be tested for Down syndrome based on a physical examination.

The first test, a rapid blood test (FISH), confirms the presence of extra material from chromosome 21. Results are available within a few days.

A karyotype test is a blood test that takes about 1-2 weeks for results. This provides further information on the type of Down syndrome, which is important in determining the chance of trisomy 21 in a future pregnancy.

How is Down syndrome treated?

While there is no cure for Down syndrome, there are a variety of treatments and therapies to address a child’s unique medical issues and developmental profile.

Medical treatment

Almost half of children with Down syndrome are born with congenital heart defects. Babies with congenital heart conditions are treated by pediatric cardiologists, doctors who specialize in diagnosing and treating heart problems.

Treatment is based on the severity of the child’s heart condition. Some mild heart defects don’t require any treatment. Others can be treated with medications, interventional procedures or surgery.

Depending on the child’s other medical issues, medications can treat conditions like seizure disorders, hypothyroidism and childhood leukemia. Surgery may be necessary to treat upper neck abnormalities and stomach problems.

Physical and behavioral therapies

A variety of therapies are available to address a child’s unique physical, behavioral and communication needs and can have a significant positive impact on children’s learning and development.

Therapies include:

  • occupational therapy to improve motor skills, such as using the hands and other parts of the body, and help children deal with sensory inputs from the environment
  • physical therapy to increase mobility and muscle strength and help children to work within functional limitations
  • speech therapy to help improve communication skills and self-expression
  • behavioral therapy focused on managing emotional and behavioral problems

Educational therapy

Most of the educational therapies used to address the core symptoms of Down syndrome are provided through programs run by states and local school systems.

It’s important for parents and teachers to understand that no single educational approach is right for every child. Most children with Down syndrome can spend at least some of their time in a general education classroom with typically developing peers but some children can benefit from a smaller setting with more individual support.

  • Children under age 3 who have Down syndrome or other developmental challenges are eligible to receive developmental services through state-run, federally mandated programs. These programs have different names in each state. In Massachusetts, the program is called Early Intervention, administered by the Massachusetts Department of Public Health.
  • From age 3 to age 21, children can access educational support through their public school system.

What is the long-term outlook for children with Down syndrome?

The average life span for people with Down syndrome has increased dramatically since the early 1900s. On average, people with Down syndrome live to about 55-60 years of age and some live into the 70s or 80s.

With the help of specialized educational programs and support, many children with Down syndrome learn and grow successfully. An increasing number of people with Down syndrome graduate from high school. Some young people with Down syndrome take college classes and many hold jobs in the community after they finish school. Some adults with Down syndrome live independently or in community based homes or supported living arrangements, where they can get additional support depending on their needs.

Prenatal Testing & Diagnosis

There are two types of tests for Down syndrome that can be performed before your baby is born: screening tests and diagnostic tests.


Prenatal screenings estimate the chance of the fetus having Down syndrome. These tests do not tell you for sure whether your fetus has Down syndrome; they only provide a probability. Diagnostic tests, on the other hand, can provide a definitive diagnosis with almost 100% accuracy.

There is an extensive menu of prenatal screening tests now available for pregnant women. Most of these screening tests involve a blood test and an ultrasound (sonogram). The blood tests (or serum screening tests) measure quantities of various substances in the blood of the mother, including alpha-fetoprotein, inhibin A, plasma protein A,estriol, and human chorionic gonadotropin. Together with a woman’s age, these are used to estimate her chance of having a child with Down syndrome. Typically offered in the first and second trimesters, maternal serum screening tests are only able to predict about 80% of fetuses with Down syndrome. It is important to note that none of these prenatal screens will be able to definitively diagnose Down syndrome. Instead, mothers should expect results such as, “You have a 1 in 240 chance of having a child with Down syndrome” or “You have a 1 in 872 chance of having a child with Down syndrome.”

These blood tests are often performed in conjunction with a detailed sonogram (ultrasound) to check for physical features that are associated with Down syndrome in the fetus. Recently, researchers have developed a maternal serum/ultrasound/age combination that can yield a much higher accuracy rate at an earlier stage in the pregnancy. Even with the ultrasound, however, the screen will not definitively diagnose Down syndrome.

In recent years, noninvasive prenatal screening tests have been made available. These tests involve blood being taken from the expectant mother as early as 10 weeks of gestation. It relies on the detection of cell-free DNA that circulates between the fetus and the expectant mother. According to the latest research, this blood test can detect up to 98.6% of fetuses with trisomy 21. A “positive” result on the test means that there is a 98.6% chance that the fetus has trisomy 21; a “negative” result on the test means that there is a 99.8% chance that the fetus does not have trisomy 21. The turn around time for the test is about 8-10 days, and approximately 0.8% of the time, results are not obtained from the tests due to technical standards. While the initial clinical trials were conducted just on cases with trisomy 21, one form of Down syndrome, a “positive” result cannot distinguish between trisomy 21, translocation Down syndrome and high-percentage mosaic Down syndrome. Put another way, a “positive” result will pick up all forms of Down syndrome, except mosaic Down syndrome that is 33% or lower. All mothers who receive a “positive” result on this test are encouraged to confirm the diagnosis with one of the diagnostic procedures described below.

Prenatal screening tests are now routinely offered to women of all ages. If the chance of having a child with Down syndrome appears high during prenatal screening, doctors will often advise a mother to undergo diagnostic testing.


The diagnostic procedures available for prenatal diagnosis of Down syndrome are chorionic villus sampling (CVS) and amniocentesis. These procedures, which carry up to a 1% risk of causing a spontaneous termination (miscarriage), are nearly 100% accurate in diagnosing Down syndrome. Amniocentesis is usually performed in the second trimester between 15 and 22 weeks of gestation, CVS in the first trimester between 9 and 14 weeks. Amniocentesis and CVS are also able to distinguish between these genetic types of Down syndrome: trisomy 21, translocation Down syndrome, and mosaic Down syndrome.

Why Should I Get a Prenatal Test?

Some mothers choose to forgo all diagnostic testing because they know that they would continue their pregnancy no matter what and do not want to expose their pregnancy to even the small risk of miscarriage that come with CVS and amniocentesis. Some start with a prenatal screen and then proceed to a definitive diagnostic test. Other mothers simply bypass the prenatal screen and start with a definitive diagnostic test. Whether or not to undergo a prenatal screening or diagnostic test is a personal decision, and expectant parents must make the choice that is best for them.


  • ADVANCED AWARENESS: Some parents would like to know as soon as possible if their fetus has Down syndrome so that they could make preparations (like informing other family members and doing research on Down syndrome) prior to the birth. Families who have chosen this option have reported in research studies that the birth of their child with Down syndrome is as much of a celebratory process as any other birth because they have had time to adjust to the new diagnosis.
  • ADOPTION: Some parents would like to receive a prenatal diagnosis so that they could make arrangements for adoption if their fetus were to have Down syndrome. There is a long waiting list of families in the United States ready to adopt a child with Down syndrome. (See below)
  • TERMINATION: Some parents want to have a prenatal diagnosis so that they can discontinue their pregnancy. Parents should discuss this option with their obstetrician.

One of the best ways to begin to consider these choices is to speak to family members of individuals with Down syndrome through a local Down syndrome organization. In addition, there are many books and articles written by family members about their personal experiences. A message from families that is echoed again and again is that the positive impacts of having a member with Down syndrome far outweigh any difficulties or challenges that may come up.

If you have any questions about these procedures, do not hesitate to ask your doctor. It is important that you receive accurate information and understand all your options.

Diagnosing Down Syndrome

Since many expectant parents choose to forgo prenatal tests, most cases of Down syndrome are diagnosed after the baby is born. Doctors will usually suspect Down syndrome if certain physical characteristics are present.


  • Low muscle tone
  • A flat facial profile
  • A small nose
  • An upward slant to the eyes
  • A single deep crease across the center of the palm
  • An excessive ability to extend the joints
  • Small skin folds on the inner corner of the eyes
  • Excessive space between large and second toe

Not all babies with Down syndrome have all these characteristics, and many of these features can be found, to some extent, in individuals who do not have the condition. Therefore, doctors must perform a special test called a karyotype before making a definitive diagnosis. To obtain a karyotype, doctors draw a blood sample to examine your baby’s cells. They photograph the chromosomes and then group them by size, number and shape. By examining the karyotype, they can determine accurately whether or not your baby has Down syndrome.

Down Syndrome: Diagnosis and Tests

How do doctors diagnose Down syndrome?

Doctors can diagnose Down syndrome before a baby is born or at birth. People may choose to participate in counseling or join a support group if they find out the baby they are carrying has Down syndrome.

In prenatal (before birth) tests called screenings, a doctor may use blood tests and ultrasound (imaging test) to look for “markers” that suggest Down syndrome may be present.

Other prenatal screenings doctors use to diagnose Down syndrome include amniocentesis and chorionic villus sampling (CVS).

In these tests, a doctor removes a sample of cells from the part of the womb called the placenta (CVS), or the fluid surrounding the baby (amniocentesis), to look for abnormal chromosomes. Parents can choose whether or not to have these prenatal screenings.

At birth, doctors perform a physical exam to look for the physical signs of Down syndrome. To confirm the diagnosis, doctors use a blood test called a karyotype. In this test, the doctor takes a small sample of blood and studies it under a microscope to see if an extra amount of chromosome 21 is present.

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