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Infant - newborn development

Contents of this page:


Skull of a newborn
Skull of a newborn
Infantile reflexes
Infantile reflexes
Developmental milestones
Developmental milestones
Moro reflex
Moro reflex

Information    Return to top

Infant development is usually divided into the following areas:


The physical development of the infant begins at the head, then progresses to other parts of the body (for example, sucking comes before sitting, which comes before walking).

Newborn - 2 months

3 - 4 months

5 - 6 months

6 - 9 months

9 - 12 months



Crying is a vitally important means of communication. By the third day of life, mothers can tell their own baby's cry from that of other babies. By the first month of life, most parents can tell if their baby's cry means hunger, pain, or anger. Crying also causes a nursing mother's milk to letdown (fill the breast). The inherent biological response in most humans to an infant's crying ensures the infant's survival.

The amount of crying in the first 3 months varies in a healthy infant, from 1 - 3 hours a day. Infants who cry more than 3 hours a day are often described as having colic.Colic in infants is rarely due to a problem with the body.

Excessive crying can be associated with child abuse. Regardless of the cause, it is a complex problem that deserves a medical evaluation.

0-2 months

2-4 months

4-6 months

6-9 months

9-12 months


The behavior of the newborn is characterized by six states of consciousness:

The ability to move smoothly from one state to another is one of the most reliable signs of nervous system maturity and health. Heart rate, breathing, muscle tone, and body movements vary with each state.

Many bodily functions are not stable in the first months after birth. This variability is normal and differs from infant to infant. Stress and stimulation can affect:

Periodic breathing, in which breathing starts and stops again, is normal and is not a sign of SIDS (sudden infant death syndrome). Some infants will vomit or spit up after each feeding, but have nothing physically wrong with them. They continue to gain weight and develop normally.

Other infants grunt and groan distressfully while making a bowel movement but produce soft, blood-free stools, and their growth and feeding remain good. This is due to immature abdominal muscles used for pushing and does not require any intervention.

Sleep/wake cycles vary and do not stabilize until a baby is 3 months old. These cycles occur in random intervals of 30 - 50 minutes at birth and gradually increase as the infant matures. By age 4 months, most infants will have one 5-hour period of uninterrupted sleep per day.

Breast-fed infants will feed about every 2 hours. Formula-fed infants should be able to go 3 hours between feedings. During periods of rapid growth, they may feed more often.

Giving the baby water is not necessary and could be dangerous. An infant who is drinking enough will produce 6 - 8 wet diapers in a 24-hour period. Teaching the infant to suck a pacifier or his or her own thumb provides comfort between feedings.


Safety is very important for infants. Base safety on the child's developmental stage. For example, around age 4 - 6 months, the infant may begin to roll over. Therefore, take extreme caution while the baby is on the changing table.

Consider the following important safety tips:


References    Return to top

Kimmel SR, Ratliff-Schaub K. Growth and development. In: Rakel RE. Textbook of Family Medicine. 7th ed. Philadelphia, Pa: Saunders Elsevier; 2007: chap 31.

Update Date: 2/27/2009

Updated by: Jennifer K. Mannheim, CPNP, private practice, Seattle, WA. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.

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