User blog comment:Zf6hellion/Zf6hellion's Shitty Guide to Characters: Fullbringers/@comment-18812574-20150323210823/@comment-1493741-20150323221911

Jokes at your expense are my forte.

I wrote that part two months ago, so I don't really have an answer for the lack of clarity on it. I'll change it.

I doubt its anything so complex. More, I've always seen it that Hollow Reiryoku is pervasive and naturally corruptive. It works to pervade everything that it can. As a result, it lingers in those attacked by Hollows, whether in wounds or elsewhere. The energy collects together within that person, but it can't really go anywhere else as the mother, by this point, is more-or-less matured and her body is less susceptible to anything the Reiryoku can do. Instead, it migrates, and attaches itself to an immature soul of a baby while the mother is pregnant.