This isn't a substantial argument, and it's sort of overused, but it's something that's been bothering me.
In a normal pregnancy, you hear things like "How's the baby?", "The baby's due on July 8th.", "She's kicking!", or "He's very healthy.". If someone kills a "wanted" prenate, you hear "He killed the baby!". (Though some people in the hardcore pro-abortion camp won't do this).
But if we're pondering prenaticide, there's a huge switch to the abstract. There's talk about "terminating the pregnancy", or "removing the products of conception", or, in the case of multiples, "reducing the fetuses".
There's a huge attempt to dance around the issue. There's references to "choice", and "reproductive rights", and "controlling one's fertility".