Down syndrome can be detected

At the beginning of March, Lidové noviny published an interesting article by our head physician of GHC Genetics MUDr. Zdeňka Vlčková on Down syndrome, which you can read below.

Down syndrome can be detected

A healthy person has 46 pairs of chromosomes, one of the pair from the mother, the other from the father. In trisomy, three chromosomes are present instead of two chromosomes of a particular pair. The most common is trisomy of chromosome 21 - Down syndrome (DS). Signs of DS are already visible in the newborn, and as the child grows, we see other signs of the disease - smaller stature, strong physique, delayed psychomotor development. Children with DS usually require specialised education and are more likely to find employment in a sheltered environment as adults.

The risk of DS increases for offspring of older mothers. The reason for the high risk of DS lies in the age of the eggs, as they are present in the woman's body as early as the 20th week of her intrauterine development and age with her from then on. Thus, the eggs of a 40-year-old woman are more than 40 years old, and the risk of DS increases with aging.

The risk of developing DS, regardless of the age of the mother, is about 1/800-1/1000, and about 1/40 at age 45. Couples planning to have children at an older age and pregnant women over 35 years of age are therefore recommended to have a genetic consultation to consider a more detailed examination. Termination of pregnancy for genetic indication can be performed at the 24th week of pregnancy at the latest.

Screening in the first trimester from the 11th to 13th week of pregnancy is already aimed at detecting DS. The examination includes a maternal blood test and a detailed ultrasound examination of the fetus, which focuses, among other things, on the so-called nuchal translucency and the presence of the nasal bone (in DS, the nuchal translucency is usually wide and the nasal bone is absent). To rule out DS in the fetus, examination of fetal cells obtained from amniotic fluid or chorionic villi is routinely recommended for women over 35 years of age.

This is an invasive prenatal diagnosis where the risk of pregnancy complications cannot be completely ruled out. Several tests are now being offered to women to look for the risk of DS in the fetus. This is the isolation of fetal DNA from the mother's blood. Recently introduced non-invasive testing (NIPT) of free fetal DNA (fetal DNA that appears in the mother's blood) detects DS (or other chromosomal defects) with 98-99 percent reliability. This type of test is not covered by health insurance companies.

Head Physician MUDr. ZDĚNKA VLČKOVÁ

Head physician of the Department of Clinical Genetics at GHC Genetics