Glossary

Maternal Serum Screening is a blood test taken between 9 and 13 weeks of pregnancy that can be used in combination  with the 12-13 week ultrasound for  risk calculation  of Down syndrome. The blood test measures the levels of two pregnancy proteins called PAPP-A (Pregnancy Associated Plasma Protein A) and Beta HCG ( Human Chorionic Gonadotropin). The profile of these hormones tends to be different in a woman carrying a baby with Down syndrome.

Nuchal Translucency Measurement: The measurement of the fluid layer in the back of the neck.

Combined First Trimester Screening (CFTS) is a screening test for Down syndrome. This test combines Maternal Serum Screen (MSS) with a 12-13 week ultrasound. The ultrasound uses measurement of Nuchal Translucency (NT), a developmental layer of fluid behind the fetal neck which is present from 11 to 14 weeks, together with other ultrasound markers for chromosomal abnormalities. This is analysed statistically against pregnancy proteins in the pregnant woman’s blood using the Fetal Medicine Foundation algorithm.

Down syndrome or Trisomy 21: is the most common chromosomal condition seen in children and adults. It is caused by an extra copy of chromosome 21. People with Down syndrome have some degree of intellectual disability and may have other health and developmental concerns.Edwards syndrome or Trisomy 18: is less common than Down syndrome and is caused by an extra chromosome 18. Pregnancies with trisomy 18 usually miscarry and babies that are live born rarely survive beyond a few weeks of life. All babies with Edwards syndrome have severe physical and intellectual problems.

Patau syndrome or Trisomy 13:  It is caused by an extra copy of chromosome 13. Pregnancies with trisomy 13 usually miscarry and babies that are liveborn rarely survive beyond the first few weeks of life. All babies with Patau syndrome have serious health problems.

Sex chromosomes: The X and Y chromosomes determine if a baby will be male or female. A normal female is XX and a male is XY. Sex chromosome conditions are caused by changes in the number of the X and Y chromosomes present.

Turner syndrome (Monosomy X): females who have only one X chromosome instead of two. There is a lethal form which women usually miscarry and a milder form with liveborn children with heart defects, developmental issues and infertility.

Klinefelter syndrome (XXY): males with Klinefelter syndrome have an extra X chromosome. This can cause some developmental and behavioural problems and infertility. Approximately 1 in 1000 babies are born with Klinefelter syndrome.

Triple X syndrome (XXX): Girls with Triple X syndrome have an extra X chromosome. Girls with this condition may be taller than average and may experience learning difficulties or behavioral problems. Approximately 1 in 800 girls will be born with an extra X chromosome.

Jacob syndrome (XYY): Boys with Jacob syndrome have an extra Y chromosome (XYY). Most babies with XYY syndrome do not have any birth defects. Boys with XYY may be taller than average and have an increased risk for learning, speech, and behavioral problems. Approximately 1 in 650 boys will be born with an extra Y chromosome.

Triploidy: Babies with triploidy have a complete extra set of chromosomes. They have a total of 69 chromosomes instead of the usual 46. At 10 weeks gestation, one in 1,000 pregnancies is affected by triploidy. It is extremely rare for these pregnancies to reach term as they typically miscarry early in pregnancy. Liveborns usually pass away within days of delivery due to heart, brain, and kidney problems. Babies with triploidy also often have birth defects affecting the extremities and face.

Carrying a baby with triploidy can increase a mother’s risk for a variety of conditions: pre-eclampsia (which can lead to seizures) and excessive bleeding after delivery. In rare instances, triploid pregnancies can persist and progress to a type of cancer called choriocarcinoma. Knowing about triploidy allows the physician to monitor the health of the mother appropriately. Panorama is currently the only NIPT that tests for triploidy.

Microdeletions: are caused when a chromosome is missing a small piece. The severity of problems caused by a microdeletion is determined primarily by the size and location of the deletion. For instance, features of the 22q deletion syndrome tend to be different and may be less severe than Angelman syndrome, which is a microdeletion involving chromosome 15.

22q deletion syndrome: Also called DiGeorge syndrome or Velo-Cardio-Facial syndrome (VCFS), is caused by a missing piece of chromosome number 22. About one in every 2,000 babies is born with the 22q deletion syndrome. The majority of children with this disorder have heart defects, immune system problems, and specific facial features. Most children with 22q deletion syndrome have mild to moderate intellectual disability and speech delays; some will also have low calcium levels, kidney problems, feeding problems and/or seizures. About one in five children with the 22q deletion syndrome have autism spectrum disorder; 1 in 4 adults with 22q deletion syndrome have a psychiatric illness, such as schizophrenia.

Prader-Willi syndrome: occurs when either a small piece of chromosome 15 is missing or when both copies of chromosome 15 come from the same parent (called uniparental disomy, or UPD). Babies with Prader-Willi syndrome have low muscle tone and problems with growth and feeding. Children with Prader-Willi syndrome have delayed milestones, short stature, rapid weight gain leading to obesity, and intellectual disability. About 1 in 10,000 babies are born with Prader-Willi syndrome.

Angelman syndrome: happens when either a small piece of chromosome 15 is missing, or when both copies of chromosome 15 come from the same parent (called uniparental disomy, or UPD). About 1 in 12,000 babies are born with Angelman syndrome. Babies and children with Angelman syndrome have severe intellectual disability, delayed milestones, seizures, and problems with balance and walking.

1p36 deletion syndrome: Also referred to as Monosomy 1p36 syndrome, is caused by a missing piece of chromosome 1. Children with 1p36 deletion syndrome have intellectual disabilities. Most have heart defects and weak muscle tone. About half of affected individuals have seizures (epilepsy), behavioral problems and hearing loss. Some children with 1p36 deletion syndrome also have vision problems or additional birth defects of other organs. About 1 in 5,000 newborn babies has 1p36 deletion syndrome.

Cri-du-chat syndrome: A missing piece of chromosome 5 causes Cri-du-chat syndrome, also called 5p- (5p minus) syndrome. The name “Cri-du-chat” was given to this syndrome due to the high-pitched, cat-like cry that babies with this syndrome often make. Babies with Cri-du-chat syndrome typically have low birth weight, a small head size and weak muscle tone. Feeding and breathing problems are common in infancy. Children with this disorder have moderate-to-severe intellectual disability, including speech and language delays. They may also have heart defects, growth delays, behavior problems, and some have curvature of the spine (scoliosis). About one in every 20,000 babies is born with Cri-du-chat syndrome.