Trisomy 2 mosaicism is a rare chromosome disorder characterized by having an extra copy of chromosome 2 in a proportion, but not all, of a person's cells. In infants born with Trisomy 2 mosaicism, severity as well as signs and symptoms vary widely. Features of Trisomy 2 mosaicism may include intrauterine growth restriction (IUGR), any of various birth defects, distinctive facial features, growth delay, developmental delays, and intellectual disabilities. The severity and specific symptoms present generally depend on the level of mosaicism (the proportion of cells affected) and the location or type of affected cells in the body. Trisomy 2 mosaicism is not inherited. It is caused by a random error in cell division during early development of the embryo. When Trisomy 2 mosaicism is detected during early pregnancy with chorionic villus sampling (CVS), the affected cells may be confined only to the placenta, and not present in the fetus. Amniocentesis may be recommended to confirm the results of the CVS, and monitoring may occur to detect intrauterine growth restriction, low amniotic fluid level (oligohydramnios), or other complications including stillbirth.