Risk of trisomy 21

Everyone knows Down's syndrome , but not everyone knows that this disease is also called trisomy 21, since it is in this pair of chromosomes that extra cells appear. This is the most common chromosomal pathology, so it is most fully studied by scientists.

The risk of the appearance of trisomy 21 pairs of chromosomes in the fetus is in all women. He averaged 1 case for 800 pregnancies. It increases if the expectant mother is less than 18 years old, or more than 35 years old, and also if the family has cases of the birth of children with deviations at the gene level.

To detect this anomaly, it is recommended to take a combined test consisting of a blood test and ultrasound. The result is the determination of the probability of trisomy 21 in a baby still in the womb. But it is not always possible to understand the information issued by the laboratory, for this it is necessary to go to the doctor, which is often impossible to do immediately.

In order not to torment yourself with guesses and feelings, from this article you will learn what the basic and individual risk of trisomy 21 means and how to decipher their meanings.

Baseline risk of trisomy 21

Under the baseline risk of Down's syndrome, a proportion indicating the number of expectant mothers with the same parameters meets one case of this anomaly is implied. That is, if the indicator is 1: 2345, it means that this syndrome occurs in 1 woman among 2345. This parameter increases, depending on the age: 20-24 - over 1: 1500, from 24 to 30 years - up to 1 : 1000, from 35 to 40 - 1: 214, and after 45 - 1:19.

This indicator is calculated by scientists for each age, it is chosen by the program on the basis of data on your age and the exact period of pregnancy.

Individual risk of trisomy 21

To obtain this indicator, ultrasound data taken during the 11-13 weeks of pregnancy (especially the size of the collar zone in a child is important), a biochemical analysis of the blood and individual data of a woman (available chronic diseases, bad habits, race, weight and number of fetuses).

If trisomy 21 is above the cut-off threshold (baseline risk), then this woman has a high (or else they write "increased") risk. For example: the base risk is 1: 500, then the result 1: 450 is considered higher. In this case, they are sent to a consultation for genetics followed by an invasive diagnosis (puncture).

If trisomy 21 is below the cutoff threshold, then in this case, the low risk of this pathology. For more accurate results, it is recommended to conduct a second screening, which is done at 16-18 weeks.

Even having received a bad result, you should never give up. It is better, if time permits, to reassess the tests and not to lose heart.