After realizing the fetus said "Tails?" I have to assume it's Sonic. Initially I was interpreting his pleasure at acquiring a ring as being akin to sexual release, which sort of (in a very loose manner) connected the events; but after realizing it's probably him in utero, I'm almost back to my original assumption.

Perhaps the earring is, indeed, an unknown protective sigil, one that sucks in and contains the assailant. Were that the case, the woman might have adorned herself with it, not knowing of potential consequences, hence her surprise at the sudden apparent pregnancy - actually imprisonment (maybe both).

Because of what I just typed, I feel the need to share something less upsetting. Did you know that Tails' real name is Miles Prower? I've known that since at least Sonic Adventure on the Dreamcast, but it wasn't until I said it out loud to my wife and she laughed that I noticed it was a pun.