Having NBE's is being able to trace back to memories of being inside one's mother's womb, although it doesn't stop there. This usually encompasses memories of being in between lives or even previous lives... though this is where Near Birth Experiences crossover into Past Lives. There have been documented reports of people who remember being in their mother's womb, my oldest brother being one of the undocumented ones.
Seeing as how Scientists don't even see how proving this possibility either way, let alone the ability to prove whether or not some people have actually been able to remember their Past Lives, these are simply theories. Although Scientists can't confirm PL's, it goes without saying that they do give an explanation for why we have particular likes and dislikes (this could be genetic, though somehow I seriously doubt it).
Despite speculations, there are many people all over the world who believe without a doubt that they've recalled past lives and had NBE's. Although I can't ever remember being in my mother's womb, I do recall in between lives and I am certain that I have, indeed, lived many times before; just as the greater majority of the Project X readers have also done.