0 a rare and very serious genetic condition in which there is an additional copy of chromosome 13 in some or all of the body's cells:
A person in one room had a fetus with trisomy 13 [a chromosomal disorder that can result in severe intellectual and physical disability].
Since scientists have numbered our chromosomes 1 through 23, the name of the condition – trisomy 21, trisomy 18, or trisomy 13 – indicates the specific chromosome that carries the abnormality.
Trisomy 18 and Trisomy 13 are the only two live-born trisomies apart from trisomy 21 (Down's syndrome).
Trisomy 13 (Patau's syndrome) is characterized by forebrain and midline facial abnormalities.
