Epidemiology and Risk Factors for Down Syndrome

• Epidemiology
o Incidence in Malaysia - 1 in every 660 births (from KIWANIS)
o Used to be 1 in 950 in an earlier report published in 1989
o Incidence classified into 3 major ethnic groups:
 Malay – 1 in 981
 Chinese – 1 in 940
 Indians - 1 in 860
o Incidence according to age groups of mothers who are pregnant: (refer to graph for wider scale of age groups)
 If woman is under 30 – less than 1/1000
 If woman is pregnant at 35 – 1 /200
 If woman is pregnant at 42 – 1/60
 If woman is pregnant at 49 – 1 / 12






o About 75% of Down Syndrome babies are born to younger woman and 25% of them to older mothers. This is because mothers tend to have more children at a younger age rather than at an older age.


Frequency of different karyotypes among the studied Down syndrome cases and pooled data from worldwide surveys




Correlation of maternal age and chromosomal aberration in Down Syndrome





• Risk Factors:
o If your parents are a carrier (Balanced carrier)
o If your parents have Down Syndrome
o If mothers are pregnant at a higher age, there is an increase in risk to have a baby that has Down Syndrome. (usually over 30 years old there is a significant increase in risk)