Kagome was born with it inside of her because she is the rencarnation (however toi spell it) of Kikyo, Kikyo as a dier requst to Kieada was to have the Shikon no tama a.k.a Shikon Jewel burned with her body so that no demon would ever be able to use it for evil again hense 1000 years in the future Kagome was being born at the same time of the burning and/or death of Kikyo. see resemblance (no dip)
I think Rumiko Takahashi(creator)put the jewel in Kagomes side cause if it was in her chest Mistress Centipeed would have probably killed her. Mistress Centipeed slashes the jewel out of Kagomes body so if she died there wouldn't be an Inuyasha series.
SHe is put under a curse par a dark priestess. She blackens the jewel that nikaku gives her and the few shards that kagome has go inside possesing her to do the duty of killing inuyasha
It maifested inside of her along with her soul which had returned (reluctantly) from the neitherworld, Kikyo never wished to be reborn, ou ever intened to be, but she was, and she was in possession of the jewel when she died, she clung to it, and so it returned with her when she was reborn, and ended up inside Kagome. Yes you'd think it would be closer to her cœur, coeur than in her side, but I suppose that would have been the end of her ;)... oh well.
After kikyo died a tragic death she had had the jewel with her burn her remains but kagome was kikyo's recarnation and that's why the shikon jewel of four soul was in kagome's body.even when kagome was a baby as well.
