A baby, or infant, may be defined as a human child at the earliest stage of life. In particular, it refers to that period before they can walk, and essentially before they attain the age of one year.
The term "infant" is derived from the Latin in-fans, which means "unable to speak." Interestingly, there is no exact definition for the term infancy. "Infant" is also a legal term with the meaning of a minor, that is, any child under the age of legal adulthood.
In the case of a human baby less than one month old, it is referred to as a newborn baby or a neonate. When referring to a newborn child, this also includes the characterisation premature, post mature, and full term babies.
Around the age of one or at the stage where the child is beginning to walk, babies are subsequently referred to as toddlers. This stage of development is normally associated with the age group of 12-36 months.
Daycare centres, which contain facilities for babies, often describe all the children in their care as infants. Even when they are older than one year or may be walking, they sometimes use the term "walking infant".
Newborn Baby
Appearance
Narrow shoulders and hips, an abdomen that may possibly have a slight protrusion, and fairly short arms and legs are typically regarded as the characteristics of a newborn baby.
It is widely recognised that, at birth, the average weight of a full-term, newborn baby, is approximately 7 1/2 lbs, or 3.2 kg. However, an acceptable weight may fall within the range of 5.5-10 pounds, or 2.7-4.6 kg. The normal body length is around 14-20 inches, or 35.6-50.8 cm. However, premature babies may be considerably smaller.
The Apgar score is a recognised measure of a newborn's passage from the uterus, the major female productive organ, during the first few minutes after it is born. A newborn baby’s head is very large in proportion to the rest of its body, whilst the cranium, which is the upper part of the skull, is enormous in comparison with the size of the face.
In general, the length of an adult human skull is about 1/8 of the total body length, whilst that of a newborn is about 1/4.
At birth, there are some areas of the newborn babies skull have yet to be transformed into bone. Therefore, this leaves distinctly delicate areas known as fontanels. There are two particularly significant fontanels. The first, and largest, is a diamond-shaped anterior fontanel, positioned at the front portion of the top of the head. The second is a smaller triangular-shaped posterior fontanel, positioned at the back of the head. As the child gets older, these bones will fuse together in a natural process. The delay in a baby’s skull fusion is due to a protein called noggin.
In 1952, Dr Virginia Apgar developed a simple and reproducible method of quickly assessing the health of a newborn baby immediately after childbirth. It was called the Apgar score. It is determined by assessing the newborn baby on five simple criteria, on a scale from zero to two, and then calculating the five values relating to each criteria. The Apgar score obtained in this way will have values anywhere between zero and 10. The five criteria, based on the term APGAR, are: Appearance, Pulse, Grimace, Activity, and Respiration.