Down syndrome, also called Trisomy 21, is a condition in which a baby is born with an extra chromosome. Chromosomes contain hundreds, or even thousands, of genes. Genes carry the information that determines your traits i.e. characteristics passed on to you from your parents. With Down syndrome, the extra chromosome causes delays in the way a child develops, mentally and physically.
The physical features and medical problems associated with Down syndrome can vary from child to child. While some kids with Down syndrome need a lot of medical attention. Though Down syndrome can't be prevented, it can be detected before a child is born. The health problems that may go along with Down syndrome can be treated, and many resources are available to help kids and their families who are living with the condition.
Women older than 35 are more likely to give birth to a child with Down syndrome. Normally, there are two copies of every chromosome. In Down syndrome, there are three copies, either complete or partial, of chromosome 21. The characteristics of Down syndrome include low muscle tone, short stature, a flat nasal bridge, and a protruding tongue. Babies with Down syndrome have a higher risk of some conditions, including Alzheimer's disease and epilepsy. Doctors can use screening tests during pregnancy to estimate the probability that a child will have Down syndrome.
What is Down Syndrome?
Down syndrome is a condition in which a baby has an extra chromosome. Chromosomes are small “packages” of genes in the body. They determine how a baby’s body forms during pregnancy and how the baby’s body functions as it grows in the womb and after birth. Typically, a baby is born with 46 chromosomes. Baby 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 baby with Down syndrome might act and look similar, each person has different abilities. Baby 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.
Types of Down Syndrome in Babies
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. 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 i.e. about 3%. 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. 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 of Down Syndrome in Babies
In cases of reproduction, both parents pass their genes on to their children. These genes are carried in chromosomes. When the baby’s cells develop, each cell is supposed to receive 23 pairs of chromosomes, for 46 chromosomes total. Half of the chromosomes are from the mother, and half are from the father. In children with Down syndrome, one of the chromosomes doesn’t separate properly. The baby ends up with three copies, or an extra partial copy, of chromosome 21, instead of two. This extra chromosome causes problems as the brain and physical features develop.
The extra chromosome 21 leads to the physical features and developmental challenges that can occur among baby 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. However, 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.
Symptoms of Down Syndrome in Babies
While Down syndrome affects baby both physically and mentally, it’s very different for each baby. For some babies, the effects are mild.
No matter what symptoms a baby with Down syndrome has, early treatment is key. With the right care to develop physical and mental skills and treat medical issues, children with Down syndrome have a much better chance to reach their full abilities and live meaningful lives. Some prominent symptoms are:
- Decreased or poor muscle tone
- Short neck, with excess skin at the back of the neck
- Flattened facial profile and nose
- Small head, ears, and mouth
- Upward slanting eyes, often with a skin fold that comes out from the upper eyelid and covers the inner corner of the eye
- White spots on the colored part of the eye (called Brushfield spots)
- Wide, short hands with short fingers
- A single, deep, crease across the palm of the hand
- A deep groove between the first and second toes
- Short attention span
- Poor judgment
- Impulsive behavior
- Slow learning
- Delayed language and speech development
Health problems related to Down Syndrome
Many babies with Down syndrome have the common facial features and no other major birth defects. However, some 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.
- Hearing loss - Many have problems hearing in one or both ears, which is sometimes related to fluid buildup.
- Heart problems - About half of all babies with Down syndrome have problems with their heart’s shape or how it works.
- Obstructive sleep apnea - This is a treatable condition where breathing stops and restarts many times while sleeping.
- Problems seeing - About half of people with Down syndrome have trouble with their eyesight.
- Blood conditions, such as anemia, where you have low iron. It’s not as common, but they also have a higher chance of getting leukemia, a type of blood cancer.
- Dementia - This is an illness where you lose memory and mental skills. Signs and symptoms often start around age 50.
- Infections - People with Down syndrome may get sick more often because they tend to have weaker immune systems.
Tests and Treatment for Down Syndrome in Babies
- Nuchal translucency testing - At 11–14 weeks, an ultrasound can measure the clear space in folds of tissue behind the neck of a developing fetus.
- Triple screen or quadruple screen - At 15 to 18 weeks, this measures the quantities of various substances in the mother's blood.
- Integrated screen - This combines results from first-trimester blood and screening tests, with or without nuchal translucency, with second-trimester quadruple screening results.
- Cell-free DNA - This is a blood test that analyzes fetal DNA present in the mother's blood.
- Genetic ultrasound - At 18 to 20 weeks, doctors combine a detailed ultrasound with blood test results.
- Chorionic villus sampling - At 8 to 12 weeks, a doctor might obtain a tiny sample of placenta for analysis, using a needle inserted into the cervix or the abdomen.
- Amniocentesis - At 15 to 20 weeks, they may obtain a small amount of amniotic fluid for analysis, using a needle inserted into the abdomen.
- Percutaneous umbilical blood sampling - After 20 weeks, the doctor may take a small sample of blood from the umbilical cord for analysis, using a needle inserted into the abdomen.
A healthcare professional can also diagnose Down syndrome after a baby is born by inspecting their physical characteristics, blood, and tissue.
There is no cure for Down syndrome, but there’s a wide variety of support and educational programs that can help both people with the condition and their families. Federal law requires that states offer therapy programs for qualifying families. In these programs, special education teachers and therapists will help your child learn:
- sensory skills
- social skills
- self-help skills
- motor skills
- language and cognitive abilities
- Children with Down syndrome often meet age-related milestones. However, they may learn more slowly than other children.
School is an important part of the life of a child with Down syndrome, regardless of intellectual ability. Public and private schools support people with Down syndrome and their families with integrated classrooms and special education opportunities. Schooling allows valuable socialization and helps students with Down syndrome build important life skills.