Earlier quoted context omitted.
If there's any science of morality to be done, the most basic quantum of moral value is suffering. Sentient creatures have greater capacity for suffering, being aware of their pain and the injustice of their existence. If we are to bring it into existence, we are responsible for its suffering.
And if a presumably sentient creature is aborted before it attains sentience, has it suffered?
It has to be, otherwise the abortion debate would be very different. Aborting a somewhat conscious fetus would be much closer to murder.