What is the definition or description of: newborn freckle rash?

Pustular melanosis: There is a condition where the fetus has a rash while in the womb that is tiny little pustules. They pop, but then leave a tiny spot of pigmentation where they were. When baby born those spots almost look like freckles, but baby has never had sun exposure! Usually fades away over the first few months of life - rarely is it a permanent rash.