Final answer:
The newborn's head size is approximately one-quarter of its body size, featuring soft spots known as fontanels for birth and growth. These areas ossify post-birth, contributing to normal skull development.
Step-by-step explanation:
The newborn's head is large, approximately one-quarter of the body size, with soft pliable skull bones. This is in stark contrast to an adult's head, which makes up only about one-seventh of their total body length. The skull of a newborn features fontanels, which are broad areas made of fibrous connective tissue that allow for the skull bones to slightly change shape and help the baby pass through the birth canal during delivery. After birth, these fontanels gradually ossify, or harden, which contributes to the normal growth and shape of the skull. Because the face and mastoid process are still undeveloped at birth, this emphasizes the relative size of the head to the body.
From week 31 until birth, the fetus lays down subcutaneous fat, which prepares their skin to transition from red and wrinkled to soft and pink as it fills out the hypodermis. The lanugo, a soft, fine hair, is shed, and the nails grow to the tips of the fingers and toes.