Stages of Preemie Development

Developmental Milestones for Premature Babies

When your baby is born prematurely, the circumstances surrounding the birth can cause you stress and anxiety about your baby's well-being. The risk of complications increases the earlier your baby is born, and uncertainties about his development can heighten your concerns. Knowing how prematurity affects normal development, and what milestones to look out for in your preemie, can help you keep track of your baby's health and growth.

How Gestational Age at Birth Affects Development

By full-term (40 weeks) all organ systems in a newborn are mature and fully functioning, including the brain, lungs, heart, eyes, ears, bowel and muscles. When your baby is born earlier than 37 weeks, his systems have to continue to develop and grow outside the protected environment of your womb.

The earlier a baby is born, and the less he weighs, the more immature and fragile his systems, and the greater the chance for delays in his development.

34 to 36 Weeks

A preemie is considered late preterm if he is born between 34 and 36 weeks. It's important to note that even preemies born closer to term can have complications after birth, such as lung or cardiovascular problems that can lead to illness and developmental delays. Your doctor may overlook these problems initially because medical resources are usually more focused on babies who are born earlier.

30 to 34 Weeks

Babies born 30-34 weeks are at higher risk for lung and heart problems than preemies born near term. However, their risks are lower than very early preemies, because their lungs and hearts are more developed. They also have less risk of brain injury and feeding difficulties, and consequently growth and developmental problems, than babies born before 30 weeks gestation.

28 to 30 Weeks

Babies born very early have a greater risk of complications from under-developed lungs and heart defects. In addition, they are at risk for injury to a fragile, immature brain. They also have a greater chance of complications from being in the hospital environment, and from necessary treatments. All of these risks can have a big influence on when he reaches standard milestones.

24 to 28 Weeks

Babies born at the very lower limits of viability are the most vulnerable to complications of prematurity. They are also at greater risks from the hospital environment, from resuscitation, and from other medical treatments than those born later. Because of these considerations, they at the greatest risk for subsequent developmental delays and learning disabilities.

Complications of Prematurity

Some organ systems in preemies (especially those born earlier than 28 weeks) are more vulnerable to the complications of prematurity than others. The effect on preemie development depends on the severity of the complications. When multiple premature organ systems are affected, there is a greater chance of long-term developmental consequences.


Events which affect the brain can lead to neurologic and developmental problems, and learning disabilities. Your premature baby's brain is especially vulnerable to:

  • Brain injury from birth trauma and hospitalization
  • Medical treatment of his complications, such as lung therapy
  • Increased risk of intraventricular brain hemorrhage (IVH) (especially babies born before 30 weeks

Even the environment of the Neonatal Intensive Care Unit (NICU), and how you, your partner and family interact with your baby, will influence brain maturation, and your baby's well-being and development.


Premature lungs are not fully-developed and may lack surfactant which keeps the air sacs (alveoli) open. The resulting respiratory distress syndrome (RDS) is common in premature babies born before 28 weeks. Premature babies have a greater risk of:

  • Resuscitation because the baby is not breathing
  • Intubation and need for life support
  • Complications from oxygen therapy
  • Infections in lungs which can affect other organ systems
  • Lung injury from necessary medical treatment
  • Long-term lung disease
  • Brain injury
  • Poor weight gain
  • Developmental delays

Cardiovascular System

Preterm babies (especially those born before 30 weeks or weigh less than 1500 grams), are at greater risk for patent ductus arteriosus (PDA), in which a heart duct does not close. Complications of PDA include:

  • Poor oxygen supply to tissues, especially the brain
  • Brain injury
  • Lung injury
  • Intraventricular brain hemorrhage (IVH)
  • Injury to other organ systems, such as skin and kidneys (because of the poor oxygen supply)


The following are some of the important facts to know about a premature baby's eyes:

  • The earlier a baby is born the less developed the lens and retina of the eye.
  • Babies born earlier than 30-32 weeks, or less than 1500 grams, are at greater risk for vision problems, which will affect learning development
  • Babies born before 28 weeks are more at risk for retinopathy of prematurity (ROP) a disorder of the retina

Early diagnosis and treatment of eye disease are essential to prevent severe vision impairment and learning disabilities.


Preterm babies are at greater risk for hearing impairment which can affect speech and language development, and learning, especially if not detected early. Causes of hearing impairment in the preterm infant include:

  • The cause of the early birth, such as maternal infections
  • Neonatal (newborn) infections
  • Drugs (ototoxic medicines) given to the baby during hospitalization

Babies less than 30 weeks are at greater risk for hearing impairment.


The immature bowel does not absorb nutrients well and your preemie may need intravenous feeding. Your baby may also have difficulty suckling if he is born before 34 weeks. Difficulty with nutrition leads to poor weight gain, longer hospital stays and delays in development.

Premature babies are also prone to necrotizing enterocolitis (NEC), a severe life-threatening inflammation of the bowel, which primarily affects babies born before 32 weeks, or who weigh less than 1500 grams at birth. Consequences which affect development in a preemie with NEC include:

  • Poor bowel function
  • Inadequate nutrition with failure to gain weight and thrive
  • Great risk of generalized infection and liver disease
  • Multiple bowel surgery and hospital admissions for babies who survive

Immune System

Because of an immature immune system, especially in those born before 28 weeks or weigh less than 1000 grams, preemies are at greater risk for:

  • Infections
  • Decreased ability to mount an immune response to fight an infection
  • Multiple organ system infections, including the brain

Severe systemic infections can lead to poor growth and development of your premature baby.

Your Baby's Developmental Milestones

Children rapidly acquire multiple life skills, particularly during the first few years of life. Developmental milestones are general guidelines for what most children do by a certain age range. These milestones are not set in stone, however, because every child is different.

Pediatricians track the following skill sets to see how well your baby is developing and will ask you some questions about them at each visit:

  • Social Skills
  • Learning/Cognitive Skills/Problem Solving Skills
  • Language/Communication Skills
  • Movement/Motor Skills

As your preemie develops, milestones are his progressive ability to:

  • Recognize and socialize with parents, siblings, and others; recognize himself
  • Pay attention, learn and understand his world, acquire new knowledge, retain skills and solve problems
  • Make cooing/babbling sounds which lead to learning language, speech and writing
  • Move arms and legs/Hold head up/Roll over/Sit up/Crawl/Walk/Run; hold spoon/crayon/pen
  • Respond to noise/smile at the sound of your voice/ hear and respond to his name
  • Respond to and follow visual stimuli; watch faces and follow moving objects
  • Differentiate people from objects, and interact with his environment
  • Cry, smile, laugh and make his needs known

The Centers for Disease Control and Prevention provides a list of developmental milestones for children from birth to age 5, which can help you track and keep a record on your preemie baby's development.

Adjusted Age

It's important to note that you can't compare your preemie's initial development to that of a baby born full term. You have to adjust your preemie's age for his gestational age at birth by subtracting the number of weeks he was born early from his current age.

For example, if your baby was born at 32 weeks (eight weeks early) and is now 16 weeks from birth, your preemie's adjusted age is only eight weeks. Given this, you would check his progress against two month developmental milestones, and not four month milestones.

Developmental Delay

While your preemie may initially lag behind, by two or three years, most preemies will catch up to the developmental milestones of their full-term playmates.

If your baby spends a few months in the hospital, his development may lag further from his adjusted age until he gains weight and strength. However, if there are complications because of his early birth, and he struggles to gain weight or has organ system damage, he may continue to lag and have permanent developmental impairments.


At any age during the developmental years, if your premature baby makes no progress, or regresses to any earlier milestone stage, discuss this with your baby's pediatrician. After taking him home from the hospital, observe your infant for early signs of problems. Issues to watch for include:

  • Inability to track moving objects or people
  • No response to noise or voices
  • Doesn't move arms or legs; listless/floppy
  • Doesn't respond to his parents, siblings or surroundings

As your baby grows, look for progress in:

  • Movement, such as lifting head, rolling over, sitting up, crawling, pushing up on legs, walking
  • Learning of new skills, such as bringing things to his mouth, playing simple games, learning and helping to dress himself, making gestures and sounds to make his needs known
  • Language development and speech, such as cooing, babbling, vowel and consonants sounds
  • Recognition of himself and others
  • Socialization with people, and attention to toys and other objects

Breastfeeding and Premature Baby Development

Breastfeeding plays an important role in mother-baby attachment. In addition, there are quite a few known benefits for the mother. Breast feeding also has many other known benefits for all babies. However, it is particularly important to breastfeed your preemie. Breast milk has several benefits for a premature baby:

  • Higher cognitive test scores
  • Provides valuable nutrients for a preemie's development
  • Is easier to digest than bottle formula
  • Provides immune protection not found in bottle formula
  • Lower risks of infection
  • Lower rates of NEC
  • Lower risk of long-term bowel disease
  • Lower risk of allergies

If it is difficult to nipple breastfeed, you can pump your milk or ask for donor milk so your baby can have the benefits of a steady supply of breast milk.

Monitor Your Baby

Babies require close attention but your premature baby might need even more observation. Monitor your baby's growth and development and consult your pediatrician if you have any concerns or questions about his growth or notice any delays in reaching milestones.

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Stages of Preemie Development