Maternal age is the strongest risk factor for Down's syndrome and the maternal age-specific risk of having a baby with Down's syndrome.75% of these translocations are de novo errors.Mosaicism (2.4%) and translocations (3.3%) also occur.The underlying genetic defect is trisomy 21 in 94% of cases.Translocation occurs in about 4% of cases of Down's syndrome.ĭown's syndrome is one of the most common genetic disorders, affecting 1 in 650-1,000. Some of the genetic material from chromosome 21, usually from the long arm, is moved to chromosome 14 or 22, or from the long to the short arm of chromosome 21. Translocation is another mechanism leading to Down's syndrome. Mosaicism is found in about 1.3-5% of cases but it is possible that mosaicism occurs more frequently. Non-dysjunction can occur during meiosis or from a mitotic error.ĭown's syndrome can also occur when only a segment of chromosome 21 has three copies (partial trisomy) or when the whole chromosome is triplicated but only a proportion of the cells are trisomic (mosaicism) with other cells being normal. The extra chromosomal content can occur through different mechanisms and at different points during the formation of germ cells. In about 88% of cases, the extra copy is maternally derived, through an error in cell division called non-dysjunction. The most common cause is the additional copy of an entire chromosome 21. Primary care can play an integral role in parental support, diagnosis, initial management, treatment of common medical problems and health promotion for children with Down's syndrome.

Children with Down's syndrome often function more effectively in social situations than would be predicted on the basis of their cognitive assessment results. The phenotype is variable and the degree of cognitive impairment may be mild, moderate or severe.

Children with Down's syndrome have multiple malformations, medical conditions and cognitive impairment because of the presence of extra genetic material from chromosome 21.

Risk factors of down syndrome