It's just vitiligo. It's a harmless and purely cosmetic condition. It's just a patch of skin that is missing pigment. There are a number of treatments for it, but it's harmless and doesn't need to be treated.
If a baby has a white mark darker than its skin, it could just be a birth mark. Continue to monitor the white mark in case it starts to get larger or others appear. It could be a sign of vitiglio (a certain skin condition).
Not at all. Lots of babies have birthmarks no matter what color their skin. I wouldn't worry at all. However, if it bothers you, just bring it up to your pediatrician at your next visit.
The birthmark is probably harmless. However, if the baby has white spots on any other part of his body, he could have a pigmentation disorder called Vitiligo. You should take him to a doctor if you are concerned.
If baby's doctor is concerned, he will refer baby to a skin care specialist, otherwise there is no need to be worried. Care maybe should be taken in sun exposure though, using sun screen if the area is exposed to protect it.