Ive never actually heard of unborn children being associated with tikbalangs, we have other monsters that eat unborn children (like the kikik), and we also have monster babies (tiyanak). Agree with the other commenter that tikbalangs normally don't kill people. In most movies or stories, they just like to trick people, like most other Filipino elementals. I think there was one movie/show I watched as a kid where the tikbalang raped a woman (not sure if their dong is horse-sized or human-sized lol) i dont remember the rest of the movie but perhaps that might have resulted in a pregnancy (with the baby being a tiyanak most likely).