Maybe the Babies soul picked the wrong mother, who didn't watch him.
There are so many parents who are incompetent enough to allow the likelihood of this happening that the birthrate would probably drop to 1/1000th of what it is now if every soul were as picky as you suggest.
There just are too many incompetent people in the world, and too many dangers in it to assure a reasonable expectation of safety for most people. A lot of unnatural things means a lot more dangers, and there are so many in our modern world that a normal natural level of vigilance or care isn't enough. People must be hyper vigilant to compensate for all of the additional dangers because of technology.
The vast majority of parents don't pimp out their children or murder them, so there is plenty of availability for a parent who does not. However, most parents aren't responsible enough not to allow them to swallow something they shouldn't. Accidental swallowing of dangerous things is a far more common occurrence than a parent murdering or raping their children, or performing human sacrifice or something, wouldn't you agree?
The rarity of certain extreme behaviors of people and any strong disposition to do them suggests a kind of deliberate and exceptional ignorance or acceptance of these behaviors when a soul decides to become a child of someone who has them.
That is true whether the extreme behavior is either good or bad.
Why be the child of a certain person you don't want to be their child?
I believe in cause and effect.
This accidental swallowing issue is neither rare, nor is intentional or in other words, there is no strong disposition of the parent to allow it to happen.
Your conclusion is specious.
, so sad to hear this 
