What is in the womb?

You may have heard about baby Amellia. She was born at only 21 (nearly 22) weeks of gestation, the earliest known preemie to live. Now there's Millie McDonagh born in Enlgand only one day later than Amellia. Apparently the UK prohibits abortion after 24 weeks, the age of "viability" after which a baby born premature has a non-negligible chance to survive. Millie has inspired a new bill in parliament lowering the restriction to 22 weeks, since now there's some hope that a baby that young may survive a premature birth.

The British law has at least some reason to it: A "fetus" is worth protecting if he or she can survive outside of the mother's womb. Not a very meaningful line to draw, but I think it gives the appearance of reason compared to the U.S.: baby inside mother = nothing, baby outside mother = person.

Let's set aside any policy decisions for a moment. What is in a mother's womb? If one believes that there is a human being worthy of protection in a mother's womb as long as that baby can survive on its own, then you are going to run into the current problem of better technology enabling earlier premature delivery survival. Does it make sense that a person's existence and thus protection depends upon our current level of medical knowledge?

If Amellia was born a miracle baby at 21 weeks, what was the nameless baby who was aborted today at 21 weeks? Just a choice? Just a terminated pregnancy?