Chromosomal disorders usually have lethal effect and incidence of occurrence is between 0,5% and 0,7% in alive newborns. These chromosomal disorders cause miscarriages during the course of pregnancy and they can particularly lead to spontaneous miscarriages within the first 3 months of pregnancy. Risk of recurrence is low for numerical chromosomal disorders due to their de novo characteristics. Risk of empirical recurrence is possible. But, theoretical risk of observance is higher than what happens in practise. Practically observed risks in pregnancies are lower than theoretically expected ones.
Structures of chromosomes