I would question whether the terminations are entirely about self-interest. Having had a sister with downs, I would worry more about the problems a potential child would face more than my own difficulties. My sister has given me far more benefits than troubles as a sibling, and I would imagine that would remain true as a parent of a child with a disability, but there's no denying the difficulties they would have to face themselves, and that would leave me questioning whether to move forward or not.
At the same time, I worry about our need to know everything and have the illusion of being in control. The control only goes so far, and the decisions can end up being impossible.