What other trisomy's are there besides 21 and what do they cause?

Many: Only about 1 in four conceptions go to term. The others are mostly all affected by either trisomies or monosomies, and are incompatible with survival. Most die before implantation, and a mom won't even know that conception had occurred. Many may implant, but die either before an embryo is visible (a blighted ovum) or later. Trisomies 13, 18, and 21 may survive until birth.