For simplictiy the term used should be 'human.'
Everyone understands what a human is, and there is no question that an embryo/fetus/baby is a human. It's a scientific certainty.
And that is one reason Hentoff (and I) are pro-life. To not fight dehumanization and murder of a fetus is to not fight dehumanization and murder of all humans.
True but it's not that useful as quantitative words when talking about human development. There is no difference between using embryo and fetus then using baby, child, teen, and adult. All human, different stages.
Say we were talking about drinking or smoking laws. Would you point to a kid and say "That human should not be allowed to smoke". No, if you provide the age you'd be factually correct but there are much better terms to use that would more clearly state your case and be easier to understand.