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Quad Screen

A blood test done during pregnancy to determine whether the baby is at risk for certain birth defects. This test is usually performed between the 15th and 22nd weeks of the pregnancy, but it is most accurate between the 16th and 18th weeks. The test measures levels of four pregnancy hormones:

  • Alpha-fetoprotein (AFP) – a protein produced by the baby
  • Human chorionic gonadotropin (hCG) – a hormone produced in the placenta
  • Unconjugated estriol (uE3) – a form of the hormone estrogen produced in the fetus and the placenta
  • Inhibin A -- a hormone released by the placenta

If the test does not measure levels of inhibin A, it is called the triple screen test. The test is done to find out if your baby might be at risk for certain birth defects, such as Down syndrome and birth defects of the spinal column and brain (called neural tube defects). An abnormal test result does NOT mean that your baby definitely has a birth defect. Possible next steps include:

  • Amniocentesis,which checks the AFP level in the amniotic fluid surrounding the baby
  • Tests to detect or rule out certain birth defects (such as Down syndrome)
  • Genetic counseling
  • Ultrasound to check the baby’s brain, spinal cord, kidneys, and heart


Quantitative Plasma Amino Acids

Blood test done to measure levels of all amino acids individually.

Rapid Onset

Beginning quickly without warning.

Receptive language disorder

Problems with understanding the message coming from others.



A quality found in the relationship between two versions of a gene. Individuals receive one version of a gene, called an allele, from each parent. If the alleles are different, the dominant allele will be expressed, while the effect of the other allele, called recessive, is masked. In the case of a recessive genetic disorder, an individual must inherit two copies of the mutated allele in order for the disease to be present.


Recessive gene

A gene that will be expressed only if there are two identical copies or, for a male, if one copy is present on the X chromosome.


Reciprocal translocation

When a pair of chromosomes exchange exactly the same length and area of DNA; results in a shuffling of genes.


Red blood cells

A type of cell in the body that carries oxygen to the body


When a muscle at the end of the esophagus does not close properly. This allows stomach contents to leak back, or reflux, into the esophagus and irritate it. Also known as gastoesophageal reflux or GERD.



The term "renal" refers to the kidney.



In the context of genetics, refers to the probability that an individual will be affected by a particular genetic disorder. Both genes and environment influence risk. An individual's risk may be higher because they inherit genes that cause or increase susceptibility to a disorder. Other individuals may be at higher risk because they live or work in an environment that promotes the development of the disorder.


Risk communication

In genetics, a process in which a genetic counselor or other medical professional interprets genetic test results and advises patients of the potential consequences for them and their offspring.


Collects excess particles of a metabolite or toxin.


Schizophrenia is a group of severe brain disorders in which people interpret reality abnormally. Schizophrenia may result in some combination of hallucinations, delusions and disordered thinking and behavior.

Screening test

Testing designed to identify individuals in a given population who are at higher risk for certain disorders or health problem, or who are more likely to be carrying a genetic mutation. A positive screening test only indicates a higher chance. It does not mean that the person will definitely have a disease or health problem.


Second Trimester

Weeks 13-28 of a pregnancy.


Seizure, Atonic

A generalized seizure characterized by a sudden loss of normal muscle tone during which the affected person will fall down or involuntarily drop his or her head, called a drop attack. The seizures are brief - usually less than fifteen seconds. They begin in childhood

Seizure, Atypical absence

A generalized seizure typically affecting children that can cause a partial or complete loss of consciousness and is characterized by a staring spell that usually lasts 5-30 seconds.

Seizure, Clonic

A generalized seizure characterized by rhythmic jerking movements of the arms and legs, sometimes on both sides of the body.

Seizure, Febrile

A convulsion seen in children that is triggered by a significant rise in body temperature accompanying fever without any neurological cause.

Seizure, Myoclonic

A generalized seizure characterized by jerking movements of a muscle or muscle group without loss of consciousness. Usually occur at the same time on both sides of the body.

Seizure, secondarily generalized

Seizures that start as a partial seizure (in one limited area of the brain) but then (sometimes so quickly that the partial seizure is hardly noticed) they spread throughout the brain, becoming "generalized."

Seizure, simple partial

Seizures which affect only a small region of the brain with no loss of consciousness.


A temporary abnormal electrical activity within the brain that can cause sudden muscle contractions, a decreased level of consciousness, and/or other neurological symptoms.

Seizures, Complex partial (focal)

A focal seizure is in which abnormal electrical disturbances remain in a limited area of the brain, affecting behavior and awareness or memory of events before, during, and immediately after the seizure.

Seizures, tonic

Brief generalized seizures, usually less than 60 seconds, consisting of sudden onset of increased tone in extensor muscles.

Seizures, tonic-clonic

A generalized seizure involving the entire body (grand mal seizure). Seizures usually involve muscle rigidity, violent muscle contractions and loss of consciousness. Also called tonic-clonic epilepsy.

Sepsis, neonatal

A whole-body, inflammatory immune system response to a blood infection that occurs in a newborn infant usually within 72 hours of birth, usually in premature neonates. The normal processes in the blood are overwhelmed, resulting in small blood clots, blocking blood flow to vital organs, which can lead to organ failure and septic shock if left untreated.

Serum or plasma ammonia level

Amount of ammonia concentration present in blood or plasma, used to monitor ammonia levels in urea cycle disorder and propionic acidemia.

Sex chromosome

The X or Y chromosome in human beings that determines the sex of an individual. Females have two X chromosomes in diploid cells; males have an X and a Y chromosome. The sex chromosomes comprise the 23rd chromosome pair in a karyotype.



Traits or diseases associated with the X or Y chromosome; generally seen in males


Single-gene disorder

Hereditary disorder caused by genetic changes that interfere with the normal function of a single gene.

Sleep apnea

A condition in which pauses in breathing (an apnea episode) occur during sleep because the airway has become narrowed, blocked, or floppy.

Sodium benzoate

A compound used in urea cycle disorders to create an alternative pathway for removal of ammonia by conjugating with glycine to form hippurate.

Sodium phenylacetate

Ammonia scavenging compound, used in combination with sodium benzoate in intravenous form to treat critically elevated ammonia levels. The trade name is Ammonul.

Sodium phenylbutyrate

Ammonia scavenging drug used in treatment of urea cycle disorders. The trade name is Buphenyl. Removes ammonia by conjugating to phenylacetylglutamine, which is then excreted from the body.


Continuous contraction of certain muscles.

Spina Bifida

A neural tube defect that frequently occurs in families. Spina bifida occurs because of an abnormality of the development of the spinal cord that occurs in the first trimester of pregnancy. Within the first 4 weeks after a fetus is conceived, the backbone and membranes that cover and protect the spinal cord and spine do not form and close properly. This can result in an opening anywhere along the spine and may cause damage to the spinal cord and nerves. The defect may be associated with a protrusion of the membrane covering the spinal cord (meninges) alone, called a meningocele, or with some neural elements, called a meningomyelocele. Or the defect may not be noticed until later in life.



An interruption of the blood supply to any part of the brain. Immediate attention is needed as brain cells begin to die. Long-term effects of a stroke include paralysis, headaches and vision problems.


A substance acted on and changed by an enzyme in any chemical reaction.


A substance added to counteract a deficiency or potential deficiency. Supplements are added to complete a thing, to make up for a deficiency or to extend or strengthen the whole; for example, calcium supplements are taken by people who may not be getting enough calcium in their diet.


The group or recognizable pattern of symptoms or abnormalities that indicate a particular trait or disease.



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