Agree whether birth is assigned the number 1 and abortion the number 2, or vice versa.
Use Random.org with a minimum of 1 and a maximum of 2.
Done!
(For the record, I don’t think an embryo is a human being at all, and a foetus, hardly. Then again, I think that, other things being equal, and if there be talk of value at all, the value of a human being depends on age. A child may have the potential to become a fully developed human being, but if it dies at twelve instead of at twenty-four, it has cost much less and therefore had much less value, anyway. (Human brains are only fully developed around the age of 25, so that’s where I’d move the age of majority.) Of course, the value of a human being likewise also declines after a certain age—unless we take “a fully developed human being” to mean the three-footed and not the two-footed Oedipus, so to say. (I mean where he has a cane, not where his ankles were just pierced and tethered together.))