Have a friend whose son will be born in Brazil in a few weeks.
Mother is Brazilian. Father is American. They live in North Carolina.
Mother arrived here on K-1 Visa and they got married.
Mother has Green Card and is now in Brazil.

If the baby is born in Brazil, does the child have to receive a Visa before the Mother and newborn Son can return to the USA?

Thanks

They will need to report the birth to the US embassy so the child will have US citizenship

But there are some pre-requisites. For example, in Colombia I had to show proof that I had been living in the U.S. for at least 5 years, among other things.

Look on your embassy's website for more information for the requisites the father needs to transfer citizenship to the child.