Affects one in 800 newborns

Individuals with Down Syndrome (Trisomy 21) are characterised by typical facial features such as an oval-shaped face and eyes that slant upwards. Most individual diagnose with Down syndrome will have some degree of learning difficulty, delayed speech development and a delay in motor development.

Approximately 50% of babies with Down syndrome are born with a heart defect and are also at risk of developing other medical conditions.

Although women of any age can have a child with Down syndrome, the chance of having a child with this condition increases with maternal age.

Affects one in 5,000 newborns

Edwards Syndrome (Trisomy 18) is due to an extra copy of chromosome 18, which is associated with a high rate of miscarriages. Many individuals with trisomy 18 die before birth or within their first month. Only 5-10% of affected children live past their first year, and often have severe intellectual disability or congenital heart defects.

Affects one in 16,000 newborns

Patau Syndrome (Trisomy 13) is due to an extra copy of chromosome 13, which is associated with a high rate of miscarriages. Many foetuses don’t survive until full-term and are stillborn or spontaneously abort. Infants born with Trisomy 13 usually have severe congenital heart defects and other medical conditions, and survival beyond the first year is rare. Features include slow growth before birth, low birth weight, heart defects, organ malformation, brain and central nervous system abnormalities and craniofacial abnormalities.

This disorder is found in individuals with an extra copy or a variation of chromosome 22 in some or all cells of their body. (Complete) Trisomy 22 is a frequent cause of spontaneous abortion during the first trimester of pregnancy, leading to the second most common cause of miscarriage after trisomy 16. Progression to the second trimester and livebirth are rare due to severe organ malformations associated with this condition.

Features associated with Trisomy 22 typically include growth delays, mental retardation, unequal development of the two sides of the body (hemidystrophy), and webbing of the neck.

Trisomy 16 is a rare chromosomal abnormality in which there are three copies of chromosome 16 rather than two. Trisomy 16 is incompatible with life and nearly all affected babies are miscarried in the first trimester. As such, it is the most common trisomy leading to miscarriage.

Trisomy 9 is a rare trisomy affecting the ninth chromosome either as full trisomy, trisomy mosaic or partial trisomy. Full trisomy 9 is always fatal; most babies with full trisomy 9 are miscarried in the first trimester. Those that make it to birth typically will not survive more than a few months, with most dying in the first week of life. Partial trisomy 9 and mosaic trisomy 9 have a more uncertain prognosis. Many babies with mosaic trisomy 9 die in infancy and those that survive usually have severe developmental impairments such as structural malformation to the heart (i.e. congenital heart defect). Partial trisomy 9 may not affect the baby's life expectancy, but affected babies may have a range of common health and developmental problems.

Affects one in 1,000 females

Triple X syndrome results from an extra copy of the X chromosome in each of a female's cells.

Females with this condition may be taller than average, but it typically causes no unusual physical features. Most females have normal sexual development and are able to conceive children. There is an associated risk of learning disabilities and delayed development of speech, language and motor skills. Seizures or kidney abnormalities occur in about 10% of affected females.

Affects one in 2,500 females

Most often, Turner syndrome results when one X chromosome is normal and the other X chromosome is missing or altered.

The most common feature of Turner syndrome is short stature, which becomes evident by about age 5. An early loss of ovarian function is also very common. Up to half of affected females are born with a heart defect, complications of which can be life threatening. However, most girls and women with the condition have normal intelligence.

Affects one in 500 to 1,000 males

Most often, Klinefelter syndrome is the result of at least one extra copy of the X chromosome in each cell. The condition interferes with sexual development, such as reduced levels of testosterone, which can lead to delayed, or incomplete puberty, breast enlargement, reduced facial and body hair, and infertility. It also causes abnormal functioning of the testes.

Affects one in 1,000 males

Jacob’s syndrome is the result of one extra copy of the Y chromosome in each cell. Although males with this condition may be taller than average, this chromosomal change typically causes no unusual physical features. Most have normal sexual development and are able to father children.

There is an increased risk of learning disabilities and delayed development of speech, language and motor skills. A small percentage of males are diagnosed with autistic spectrum disorders, which are developmental conditions that affect communication and social interaction.

Affects one in 20,000 to 50,000 newborns

This condition results when a piece of chromosome 5 is missing. Affected infants have a high-pitched cry that sounds like a cat, hence the name Cri-du-chat (cat's cry).

It causes intellectual disability and delayed development, small head size, low birth weight, and weak muscle tone in infancy. Affected individuals also have distinctive facial features, including widely set eyes, low-set ears, a small jaw and a rounded face. Some infants with Cri-du-chat syndrome are born with a heart defect. As they grow, people with cri-du-chat usually have difficulty walking and talking. They may have behavioural problems and severe intellectual disability.

Affects one in 5,000 to 10,000 newborns

This condition results when a piece of chromosome 1 is missing, and typically causes severe intellectual disability. Most affected individuals have limited or no speech, as well as behaviour problems. Most have structural abnormalities of the brain resulting in seizures. There may also be weak muscle tone and swallowing difficulties.

Physical characteristics include a small head that is also unusually short and wide in proportion to its size. There might also be vision or hearing problems, and abnormalities of the skeleton, heart, gastrointestinal system and other organs.

This rare condition results when a piece of chromosome 2 is missing. It affects the motor neurons, which are the specialised nerve cells in the brain and spinal cord that control the movement of muscles. The disorder usually causes severe mental retardation and behaviour problems.

This condition results when a piece of chromosome 16 is missing. Common clinical features for 16p12.2 deletion includes: a delay in starting to speak, a degree of developmental delay or learning difficulty, growth impairment, a cardiac malformation, epilepsy and mild dysmorphic facial features without a consistent pattern.

Affects one in 100,000 newborns

Jacobsen syndrome, which is also known as 11q terminal deletion disorder, is caused by a deletion of genetic material at the long (q) arm of chromosome 11. Most affected individual have delayed development in motor skills and speech, with most having cognitive and learning difficulties and distinctive facial features such as small/low set ears, widely set eyes and large head size. More than 90% of people with Jacobsen syndrome have bleeding disorder call Paris-Trousseau syndrome that causes lifelong risk of abnormal bleeding and easy bruising.

Affects one in 35,000 to 100,000 newborns

Van de Woude syndrome is a condition that affects the development of the face. Many people with this disorder are born with a cleft lip, a cleft palate (an opening in the roof of the mouth), and have an increased risk of delayed language development, learning disabilities, or other mild cognitive problems. Van der Woude syndrome is usually caused by mutations in the interferon regulatory factor 6 (IRF6) gene which is typically encoded in region on chromosomes

Angelman syndrome affects one in 12,000 newborns whereas Prader Willi syndrome affects one in 20,000 to 50,000 newborns

Most mothers carrying babies with a 15q11.2 microdeletion experienced no pregnancy problems, had a normal delivery and only discovered their baby was affected after the birth. There are two main types of syndrome associated with this microdeletion.

Angelman syndrome results from a loss of gene activity (expression). Main characteristics of Angelman syndrome includes severe mental retardation, lack of speech, excessive happy demeanour. Prader Willi syndrome is caused by a loss of active genes in a region of chromosome 15. People can have either Prader-Willi syndrome or Angelman syndrome. Characteristics of Prader-Willi syndrome includes mild to moderate development delay, delayed to no puberty.