Incidence-prenatal diagnosis
Maternal factor : The incidence of Down Syndrome in babies born to women under 20 years of age is less than one in 2000. However, the risk rises to almost one in 20 at the age of 45. The steepest increment in incidence with maternal age occurs at the age of 35. However, 50% of mothers who give birth to Down Syndrome children are less than 35 years old.
Paternal factor : The ageing sperm (the longer it is stored in the genitourinary tract the greater is the incidence of sperm-derived trisomies) and decreased sexual frequency particularly among older couples or teenage couples who live apart, increase risk of babies born with Down Syndrome.
Environmental Factors : X-rays, exposure to radiation, viruses, hormonal factors are still being researched into, in the context of chromosomal events.
Inherent Biological Vulnerability Factors : One study showed the cells of mother of children with Down Syndrome to have a variation of microtubular function, the microtubles forming the spindle on which the separation of the chromosomes take place at the time of cell division. However, this is still under research.
