Structure and Function: The Newborn Baby

A full-term newborn baby weighs on average 3.5 kg (7 lb 11 oz), measures 51 cm (20 in) in length, and is well prepared for survival. Many aspects of a newborn’s appearance, such as the shape of the skull, are a result of the transition from the uterus to the outside world and are different from those of a fetus or older child. Such differences are normal and usually disappear relatively quickly. Other structures, such as the long bones, are not yet fully formed. The baby also has primitive reflexes, such as a grasp reflex, which are important to survival but disappear with increasing age.


The bone plates of a baby’s skull are separated by fontanelles (soft gaps) and sutures (seams) that allow the plates to move and overlap during childbirth.


In a newborn baby, the eyelids are puffy and vision is poor even when the eyes are wide open.

Lanugo hair

Premature babies may have downy hair, called lanugo hair, all over the body. This hair disappears after about a month.

Umbilical cord

The umbilical cord, which is cut at delivery, shrinks and falls off within 14 days to form the navel.


At birth, the hands are often clenched and the skin is wrinkled. The tips of babies’ nails often flake off on their own and do not need cutting.

From the 2010 revision of the Complete Home Medical Guide © Dorling Kindersley Limited.

The subjects, conditions and treatments covered in this encyclopaedia are for information only and may not be covered by your insurance product should you make a claim.

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