In the Stallman case, it was not a fetus suing, it was an already born child with severe disabilities due to negligent behavior prior to the child’s birth. Obama twisted the perspective to focus upon the fetus’s ‘lack of standing’, as did the IL subpreme court in making their final ruling.
I would also note that in many states a criminal assault which harms the alive unborn is actionable as an additional crime, thus the fetus does have standing in that way.