ironic since so many people want to abort them

Those with Down Syndrome are less likely to get cancer-- and why it may help scientists deal with cancer in the broader population.

From Disaboom, citing a Harvard study (hat tip: Sevens)...

You won't find "reduced risk of cancer" on most lists of the effects of Down Syndrome (Trisomy 21), but scientists have long known that people with the condition rarely get most types of cancer. Now, a Harvard study has identified one of the factors that protects people with Down Syndrome against tumors. The discovery could lead to new methods of protecting all patients against cancer.

People with Down Syndrome have extra versions of 238 different genes due to their third copy of human chromosome 21....One of the 238 genes found in the third chromosome 21 is called Down syndrome candidate region-1 (DSCR1, also known as RCAN1). This gene...affects angiogenesis-- the process by which tumors grow blood cells to nourish themselves....

By studying induced pluripotent stem cells from a volunteers with Down Syndrome, as well as mice genetically altered to have a [similar] condition...Harvard University's Sandra Ryeom and colleagues discovered DSCR1's affect on tumor growth.