Progress in medical technology and the Neonatal Intensive Care Unit (NICU) have made the survival of smaller and smaller infants possible. As a result, we now have a new kind of human being: THE PRETERM INFANT.

Of course, preemies are in many ways small versions of the full term infant. But preemies also are very different from full term infants, and they live in a world that is very different from that of either the fetus in the womb or the full-term infant at home. Therefore, it is unfair to think of the preemie as either a fetus or a mini full-term baby: preemies are unique, and deserve unique and special treatment.

The preemie of 24 weeks gestational age would normally expect about 16 more weeks in the womb, where:

Why does my baby not act like a full-term baby?

To learn about what infant's do, it is helpful to think about five areas of development. These areas are parts of the whole system, the whole baby. These areas of development are controlled by the brain and develop in cooperation with each other.

The five areas of development are:

Because the nervous systems (brains) of preemies are not as mature as those of full-term babies, development in these five areas is not as far along as in a full-term baby.

For example, you may find your preemie has:

What Can My Baby Do?

Hearing (The Auditory System)

Hearing is fairly well developed by 20 weeks gestational age (GA).

By 25 to 28 weeks GA, the preemie responds in different ways to different sounds. For example:

What sounds do preemies hear?

Seeing (The Visual System)

Seeing takes longer to mature than hearing and touch, but progress occurs rapidly between 22 and 34 weeks of gestational age (GA).

Infants don't see as well as adults.

Sleeping and Waking - The Behavioral State System

What a baby does and how he/she reacts to what is going on depends a lot on the state of sleep or wakefulness the baby is in. For example:

Babies have two sleep states, an in-between sleep-wake state, and three wake states. At first the states are hard to tell apart, but they become more clear as the baby grows. The amount of time a baby spends in each state also changes as the baby grows. Both of these patterns of change reflect the gradual maturing of the brain and nervous system.

Sleep states

The pattern of sleep states

A full term baby spends about 15-20 minutes at a time in deep sleep and 65-70 minutes in light sleep. A young preemie may spend only 2-5 minutes in deep sleep before going back into light sleep. All infants (preemies, too) go to sleep into light sleep, and if not disturbed, wake up from light sleep.

The pattern of more light than deep sleep changes slowly over the first year to the adult pattern of spending more time in deep than light sleep. Thus a gradual increase in the amount of deep sleep shows that the brain is growing as it should.

At term age (40 weeks), preemies still do not have as much deep sleep as the full term. However, if light levels are lower at night than during the day during their "growing" period in the NICU, they may progress faster.

During each sleep period, infants go through two or three light-deep-light sleep cycles. It is important that they be able to go through this cycling. That is a big reason for trying not to disturb infants during their sleep periods.

Wake States

Just as there are levels of sleep, babies also have several levels of being awake:


Some experts describe fussing or crying as a separate behavioral state, others describe it as a behavior that can occur in many states.

The pattern of wake states

Before 26-27 weeks, it may be hard to tell whether the preemie really wakes up. There is no alert state.

Between 27 and 30 weeks the preemie usually can become alert only for a very short time. When awake, the preemie is either drowsy or active awake. The time spent alert gradually goes up as the baby grows, and the amount of active awake goes down. Thus increasing alertness is another sign that the brain is growing well.

The baby needs to be alert to attend to (think about) what he/she sees. This is a very important form of learning. Alertness is also very important for interacting with people, and therefore is related to social development.

At full term age (39-40 weeks), preemies still are not spending as much time alert as a full term baby does. However, many of the things now being done in NICU's to help preemies grow well (see section on DEVELOPMENTAL CARE) may help them be more alert earlier.


Your baby talks to you through his/her behavior and you can learn to understand or "read" your baby's behavior. You can learn who your baby is, what his/her behaviors mean, what he/she likes and doesn't like.

For example, there are cues - signs - a preemie gives when stressed and others when stable:



color changes

stable color








tremors, twitches

smooth movements


arms or legs out stiff

relaxed posture


spreading fingers wide



arching back

loosely curled up/flexed


weak/gaspy cry

rhythmic/robust cry


can't be waked up

will slowly wake up



no irritability


a lot of fussing/crying

not much fussing/crying


glassy-eyed stare, turning away

focused attention


abruptly going to sleep