ad. 20. What do specialists understand by the word “marker”?
Marker is a structural defect, image or sonographig measurement associated with a fetus with a genetic disorder. Defects are called major markers. Examples are umbilical hernia or abnormal fingers positioning of both hands in the Edwards’ syndrome, i.e. trisomy 18. Images and measurements are called soft markers. They occur more frequently in babies with genetic disorders, however, they may appear in rare cases of healthy fetuses. An example of this can be a sandal gap deformity (which is an increase in the interspace between the great toe of the foot from the rest of the toes), a shorter thigh bone (which is typical for the Down syndrome) or an increased nuchal fold thickness (characteristic of the Down syndrome but also of other disorders). An isolated occurrence of soft markers is observed quite often and is not an indication for an invasive test. Coexistence of several such markers is alarming and requires considering genetic tests.