- If a fertilized egg is a human, then the woman is responsible for the death of any human that does not attach to a uterine wall.
- The woman is not responsible for the death of the human.
- Therefore the fertilized egg is not a human and abortion is justifiable.
An abortion is not analogous to an egg that does not attach to a woman's uterine wall.
No one is blaming anyone for miscarriages or for fertilized eggs not attaching to the uterine wall because no one has done anything obviously blameworthy. The issue is the intentional abortion of a pregnancy.
Consequently, (1) is false and the argument is unsound.
If, on the other hand, intentionally aborting a pregnancy is morally blameworthy, then we have a duty to prevent it.