A newborn's head is very large in proportion to the body, and the cranium is enormous relative to his or her face. A newborn's head is very large in proportion to the body, and the cranium is enormous relative to his or her face. While the adult human skull is about one seventh of the total body length, the newborn's is about 1⁄4.
Macrocephaly is the term for an unusually large head. An infant with macrocephaly will have a larger head than most other infants of the same age and sex. In many cases, this condition is benign or harmless. In other cases, it may indicate an underlying medical condition, such as a genetic syndrome or a brain tumor.