Yes it was on the list as a defect, since in the past the children had a limited chance of survival past the parent's demise, but I think I would like to ask Wolfstar to clarify.
Wolfstar?
You don't know much about the Down's children or adults. They are capable of emotional and physical pain as well as everyone. They have heart disease and heart attacks. they know the difference between living and dying. If institutionalized, they often have anger which results in their being strai jacketed, given drugs, even beaten and killed.
Down Syndrome is on the list because it was on the list I found while Googling on the subject of common birth defects. No other reason.