Classification and external resources
Trisomy 18 or Edwards Syndrome (named after John H. Edwards, who first described the syndrome in 1960) is a genetic disorder. Chromosome 18 is one of the 23 pairs of Chromosomes in Humans People normally have two copies of this chromosome The International Statistical Classification of Diseases and Related Health Problems (most commonly known by the abbreviation ICD) provides codes to classify Diseases The International Statistical Classification of Diseases and Related Health Problems 10th Revision ( ICD -10) is a coding of diseases and signs symptoms abnormal findings Q00-Q89 - Congenital malformations and deformations (Q00-Q07 Nervous system ( Anencephaly and similar malformations Q00-Q89 - Congenital malformations and deformations (Q00-Q07 Nervous system ( Anencephaly and similar malformations The International Statistical Classification of Diseases and Related Health Problems (most commonly known by the abbreviation ICD) provides codes to classify Diseases The following is a list of codes for International Statistical Classification of Diseases and Related Health Problems. The Diseases Database is a free Website that provides information about the relationships between medical conditions Symptoms, and Medications. eMedicine is an online clinical medical knowledge base that was founded in 1996 by Scott Plantz and Richard Lavely two medical doctors John Hilton Edwards ( March 26, 1928 &ndash October 11, 2007) was a British medical Geneticist. A genetic disorder is a condition caused by abnormalities in Genes or Chromosomes While some diseases such as Cancer, are due to genetic abnormalities acquired It is the most common autosomal trisomy after Down Syndrome that carries to term. An autosome is a non-sex Chromosome. It is an ordinarily paired type of chromosome that is the same in both Sexes of a species. A trisomy is a form of Aneuploidy with the presence of three copies instead of the normal two of a particular Chromosome. Down syndrome, Down's syndrome, or trisomy 21 is a Chromosomal disorder caused by the presence of all or part of an extra 21st chromosome.
It is caused by the presence of three — instead of two — copies of chromosome 18 in a fetus or infant's cells. Chromosome 18 is one of the 23 pairs of Chromosomes in Humans People normally have two copies of this chromosome
The additional chromosome usually occurs before conception. For soil improvement see Fertilization (soil. A healthy egg or sperm cell contains individual chromosomes - one to contribute to each of the 23 pairs of chromosomes needed to form a normal cell with 46 chromosomes. Numerical errors arise at either of the two meiotic divisions and cause the failure of segregation of a chromosome into the daughter cells (non-disjunction). This results in an extra chromosome making the haploid number 24 rather than 23. Fertilization of these eggs or sperm that contain an extra chromosome results in trisomy, or three copies of a chromosome rather than two.
The survival rate of Edwards Syndrome is very low. About half die in utero. Of liveborn infants, only 50% live to 2 months, and only 5–10% will survive their first year of life. Major causes of death include apnea and heart abnormalities. It is impossible to predict the exact prognosis of an Edwards Syndrome child during pregnancy or the neonatal period. Prognosis (older Greek πρόγνωσις modern Greek πρόγνωση - literally fore-knowing foreseeing) is a medical term denoting the Pregnancy ( Latin graviditas) is the carrying of one or more offspring known as a Fetus or Embryo, inside the Uterus of a Female Because major medical interventions are routinely withheld from these children, it is difficult to determine what the survival rate or prognosis would be with aggressive medical treatment.
The rate of occurrence for Edwards Syndrome is approximately one in 3,000 (for conception) and approximately one in 6,000 (for live births), as 50% of those diagnosed prenatally with the condition will not survive the prenatal period. Although women in their 20s and 30s may conceive Edwards Syndrome babies, there is an increased risk of conceiving a child with Edwards Syndrome as a woman's age increases, with the average age for this disorder being 32½. 
A small percentage of cases occur when only some of the body's cells have an extra copy of chromosome 18, resulting in a mixed population of cells with a differing number of chromosomes. Such cases are sometimes called mosaic Edwards syndrome. In Medicine ( Genetics) a mosaic or mosaicism denotes the presence of two populations of cells with different Genotypes in one Very rarely, a piece of chromosome 18 becomes attached to another chromosome (translocated) before or after conception. In Genetics, a chromosome translocation is a Chromosome abnormality caused by rearrangement of parts between nonhomologous Chromosomes. Affected people have two copies of chromosome 18, plus extra material from chromosome 18 attached to another chromosome. With a translocation, the person has a partial trisomy for chromosome 18 and the abnormalities are often less than for the typical Edwards syndrome.
Symptoms and findings may be extremely variable from case to case. However, in many affected infants, the following may be found: