Types, signs in infants and screening during pregnancy


While Down syndrome can change the life of a baby – and a family – people with Down syndrome are living longer and more fulfilling lives than ever before. Here’s what parents and expectant parents should know about Down syndrome.

What is Down syndrome?

Down syndrome is a chromosomal disorder that causes a range of mental and physical symptoms ranging from mild to severe. Down syndrome is also called trisomy 21 because people with Down syndrome have three number 21 chromosomes instead of two.

An estimated 6,000 American babies – or about one in 700 – are born with Down syndrome each year, according to the Centers for Disease Control and Prevention (CDC).

The medical needs of children with Down’s syndrome may vary. Some children with more severe symptoms may require more care and treatment than others. However, most people with Down syndrome can lead full, healthy lives.

Types of Down syndrome

Down syndrome occurs when fetal cells develop and divide differently than is typical. It can happen in different ways, leading to different types of Down syndrome.

  • Trisomy 21 or non-disjunction is the most common type of Down syndrome, accounting for 95 percent of all cases. This happens when an embryo develops three copies of chromosome 21 instead of two.
  • Shift occurs in about 3 percent of Down syndrome cases. This happens when a full or partial copy of chromosome 21 attaches to another chromosome.
  • Mosaicism occurs in about 2 percent of Down syndrome cases. This happens when some cells have the usual 46 chromosomes while others have 47, so some cells with 47 chromosomes have an extra copy of chromosome 21.

What causes Down syndrome?

Down syndrome is caused by cell division that occurs during the formation of an embryo. When a baby is conceived, it usually receives 23 chromosomes from its mother and 23 from its father for a total of 46 chromosomes. In Down’s syndrome, a developing embryo receives an extra copy of a chromosome – chromosome 21.

Experts don’t quite understand why this happens, but maternal age may play a role. Women over 35 are more likely to have a child with Down’s syndrome than younger women, and the odds increase even more significantly for women over 40.

However, there is nothing a mother (or father) can do to “cause” a child to have Down syndrome. And there is no way to prevent it.

What are the signs of Down syndrome in infants?

A baby with Down syndrome can have physical characteristics such as:

  • A head smaller than average
  • A broad, flat face with upward slanting eyes and a short nose
  • A bigger than average tongue
  • Extra skin around the back of the neck
  • Small rounded ears set low

Infants with Down syndrome can:

  • Appear flabby or limp, due to poor muscle tone
  • Acting unusually passive and crying infrequently
  • Having sucking or feeding problems
  • You have constipation or digestive problems, or a congenital condition called duodenal atresia
  • Reach developmental milestones like sitting, crawling, or walking later than other babies
  • Are more likely to have certain types of heart defects

Screening for Down syndrome during pregnancy

Screening and diagnostic tests can detect Down syndrome early in pregnancy, usually at 20 weeks (and sometimes before 12th week).

Screening tests, which are non-invasive and low-risk, can estimate the risk of a fetus developing Down syndrome. The tests look at a sample of your blood, which contains DNA from your baby’s placenta.

While screening tests were once reserved for women over 35 or with other risk factors, the American College of Gynecologists and Obstetricians (ACOG) now recommends that all women discuss prenatal screening options with their doctor.

Commonly used non-invasive prenatal screening tests (or PNIDs) include nuchal translucency tests, cell-free DNA tests, triple or quadruple screenings, and integrated screenings. The results of the DPNI can help you and your doctor determine if more invasive diagnostic tests are needed.

Diagnostic tests can tell if a fetus has Down syndrome or another chromosomal disorder. These tests, which are more invasive and involve the collection of genetic material from a baby’s placenta or amniotic fluid, include chorionic villus sampling (CVS), amniocentesis, and cordocentesis, also called percutaneous umbilical sampling. There are pros and cons to each type of diagnostic test, so it is important to weigh the benefits and risks with your doctor before deciding which one is best for you.

If Down syndrome is suspected based on the results of prenatal diagnostic tests, the results can be confirmed with a blood test after a baby is born. However, having a diagnosis during pregnancy can help future parents prepare and align medical care that can begin immediately after birth.

Latest treatments for Down syndrome

There is no cure for Down syndrome. But thanks to improved medical care and therapy, people with Down’s Syndrome are living richer lives than a generation ago.

Children with Down’s syndrome reach developmental milestones – they may simply take longer to get there. As adults, they can work and can even live alone or in group homes.

Children with Down’s syndrome often have a team of specialists to deal with the physical and mental challenges surrounding the disorder. This team could include pediatric experts such as cardiologists, neurologists, speech-language pathologists, audiologists, occupational and physiotherapists, endocrinologists, ophthalmologists, ear, nose and throat specialists, and social workers. The treatment of an individual child will depend on their unique physical and intellectual needs.

In most cases, surgery can correct serious problems such as heart or gastrointestinal abnormalities, and early intervention therapies – which can start soon after birth – can give children with Down syndrome the best chance of reaching their potential. Early intervention services can continue until a child is 3 years old; after that, children are eligible to continue receiving the treatment they need through their local school district.


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