It is believed that most conceptions of trisomy 18 or trisomy 13 do not result in live births. Many children diagnosed in the second or third trimester will be stillborn. For live-born children, survival is not assured. read more
Affected people have two copies of chromosome 18, plus a “partial” piece of extra material from chromosome 18. Mosaic Trisomy 18: Mosaic trisomy is also very rare. It occurs when the extra chromosome is present in some (but not all) of the cells of the body. read more