Down Syndrome Risk: Probability by Age Group

As the mother ages, the risk of having a child with a chromosomal abnormality such as Down syndrome increases. Find out here why this is the case and get a statistical overview of how high the risk for Down syndrome is within the individual age groups.

Why does Down syndrome risk increase with age?

What is the relationship between maternal age and Down syndrome risk? This is directly related to the adhesive protein cohesin, which is found in the woman’s egg cells and has the function of holding the chromosomes contained in the egg cells in position. In this way, it stabilizes the chromosomes and ensures the correct sequence and timing of cell division. With increasing age, however, the adhesive protein cohesin loses its binding power or is even completely broken down. This is due to the fact that certain substances in the organism that protect the cohesin from damage and degradation dwindle with age. Aging and the associated disintegration of the cohesin can therefore also mean that the chromosomes fall apart and the faulty distribution of the genetic material during fertilization. For this reason, chromosomal abnormalities such as Down syndrome are much more likely to occur in advanced age.

Chromosomal anomalies always arise when either too much or too little genetic material is passed on from parent to child during cell division. Down syndrome, also known as trisomy 21 , is a genetic defect in which the chromosome 21 is not present only twice, as intended, but instead three times. This entails both physical and cognitive impairments for the child. As the mother-to-be grows older, the risk of a chromosomal abnormality such as Down syndrome also increases.

Statistics: The frequency of Down syndrome in relation to maternal age

The statistics presented here show the occurrence of Down syndrome in relation to maternal age. The age of the woman giving birth, the number of fetuses that develop Down syndrome up to the 16th week of pregnancy and the number of babies that are born with Down syndrome are recorded. The 16th week of pregnancy and the time of birth are stated as the point in time. This is because a significant number of miscarriages due to Down syndrome occur in the intervening period. For this reason, the probability also decreases from the 16th week of pregnancy until the birth.

ageNumber of fetuses (week 16) with/without Down syndromeNumber of births with/without Down syndrome
15 – 191 in 1250
20 – 241 in 1400
25 – 291 in 1100
30 – 311 in 900
321 in 750
331 of 4201 of 625
341 of 3251 in 500
351 in 2501 in 350
361 in 2001 of 275
371 in 1501 of 225
381 out of 1201 of 175
391 in 1001 of 140
401 of 751 in 100
411 in 601 of 85
421 of 451 of 65
431 of 351 out of 50
441 out of 301 in 40
45 and older1 out of 201 out of 25


Why is trisonomy 21 more likely to occur in children of older women?

One thing in particular is clear from the statistics: the older the mother, the higher the risk of Down syndrome occurring during pregnancy. For example, a 20-24 year old woman has a 1 in 1400 chance of giving birth to a baby with Down syndrome, while a 45 year old woman has a 1 in 25 chance. The reason for this is the age-related degradation of binding proteins, which lose strength or are broken down. This causes a maldistribution of the chromosomes in the egg cells.

Find out more about abortion for Down syndrome here , how Down syndrome can be detected early with the help of a blood test and what risks a late pregnancy can still entail.

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