The amount of vitamin K is an insane amount, I have read as much as 25,000 times the amount (give or take, depending on size of baby)
and the overload causes the body to overreact
and not absorbed correctly.
Vitamin K toxicity causes jaundice, which is already a problem facing newborns without the shot.
During the last trimester, the vitamin K levels for the mother decrease and more is passed through the placenta, therefore newborns have their own supply of vitamin K.