Premature infant

Alternative names 
Preterm infant; Preemie

A premature infant is any infant born before 37 weeks gestation.

Causes, incidence, and risk factors

Every newborn is classified at birth as one of the following: premature (less than 37 weeks gestation), full-term (37 to 42 weeks gestation), or post-term (born after 42 weeks gestation).

Preeclampsia, a condition that can develop in the second trimester of pregnancy with High blood pressure, fluid retention, and protein in the urine, may result in preterm labor. Other maternal disease processes such as kidney disease, Diabetes, infection, or heart disease may also contribute to preterm labor. Often, the cause is unknown.

Multiple pregnancy (the presence of more than one fetus in the uterus, twins etc.) accounts for 15% of all premature births.

The problems encountered by a premature infant are related to the immaturity of the organ systems. The infant requires specialized care in a nursery until his or her organ systems have developed enough to sustain life without specialized support. Depending on the extent of prematurity, this may take weeks to months.

Common problems related to immature organ systems include:

  • Respiratory complications such as hyaline membrane disease (also known as respiratory distress syndrome or RDS)  
  • Central nervous system immaturity that results in difficulty coordinating sucking and swallowing, susceptibility of bleeding into the brain, or episodes of absent breathing (apnea)  
  • Gastrointestinal immaturity that leads to feeding intolerance  
  • Kidney immaturity

Risk factors that may contribute to preterm labor include lack of prenatal care, poor nutrition, youth (mothers less than 18 years old), and substance abuse.

Problems inherent to the mother’s health include:

  • A history of a previous preterm delivery  
  • A high unexplained alpha-fetoprotein level in the second trimester  
  • Untreated disease or infection (such as urinary tract infection or infection of the amniotic membranes)  
  • Abnormalities of the uterus or cervix  
  • Premature rupture of the membranes or placenta previa

Approximately 10% of all births in the U.S. occur before 37 weeks gestation.


  • Low birth weight - less than 5.5 pounds (2500 grams)  
  • Thin, smooth, shiny, almost translucent skin  
  • Veins are easily seen through the skin (transparent skin)  
  • Wrinkled features  
  • Soft, flexible ear cartilage  
  • Body hair called lanugo  
  • Irregular breathing pattern  
  • Weak cry  
  • Usually inactive, may be unusually active immediately after birth  
  • Ineffective suck and swallow (Poor feeding)  
  • Enlarged clitoris (female infant)  
  • Small scrotum, smooth without ridges (male infant)

Signs and tests

The infant may have a low body temperature, develop Rapid breathing, or exhibit poor respiratory effort.

Common tests performed on a premature infant include the following:


When premature labor develops and cannot be stopped by medical intervention, plans for appropriate management of a premature baby and the mother are made, which may involve transport of the mother to a center with facilities to care for premature infants, i.e. a neonatal intensive care unit (NICU). In some cases, steroids may be given to the mother in order to facilitate lung maturity in the premature infant.

To assure support of the respiratory and cardiac systems and anticipate other common problems associated with prematurity, immediate evaluation and, if necessary, resuscitation takes place after delivery. The infant will be admitted to or transported to a high-risk nursery with personnel trained in the care of premature infants.

The infant is placed under a warmer or in an isolette with controlled temperatures where careful observation and care can be given.

Feeding may be administered by inserting a tube into the stomach, since infants are usually unable to coordinate sucking and swallowing before 34 weeks gestation. Intravenous feeding may be indicated in extremely premature infants.

Depending on the degree of prematurity, the infant may not start breathing after birth, or respiratory efforts may be inadequate to expand the chest and deliver oxygen to the infant’s body. In such cases, a breathing tube is inserted into the infant’s trachea, and artificial breathing is delivered by a respirator. Supplemental oxygen is given. (See respiratory distress syndrome.)

Nursery care is needed until the infant is able to take oral feedings, maintain body temperature, and achieve a body weight of about 5 pounds. However, other problems may complicate treatment, especially for very small infants, which could prolong the hospital stay.

Support Groups

There are multiple support groups for parents of premature babies. Ask the social worker in the neonatal intensive care unit.

Expectations (prognosis)

Prematurity was formerly a major cause of infant deaths. Improved medical and nursing techniques have increased the survival of premature infants. A greater chance of survival is associated with increasing length of the pregnancy. Of babies born at 28 weeks, approximately 80% survive.

Prematurity is not without long-term effects. A large proportion of premature infants have medical problems that persist into childhood or are permanent. As a rule, the more premature an infant, and the smaller the birth weight, the greater the risk of complications. It must be stressed, however, that it is impossible to predict the long-term outcome for an individual baby merely on the basis of gestational age or birth weight.


Possible complications include:

  • Hyaline membrane disease (respiratory distress syndrome)  
  • Bleeding into the brain (intraventricular hemorrhage)  
  • Retinopathy and associated visual loss or Blindness  
  • Bronchopulmonary dysplasia (BPD)  
  • Heart disease  
  • Severe intestinal inflammation (necrotizing enterocolitis)  
  • Jaundice  
  • Infection or septicemia  
  • Anemia  
  • Low blood glucose (hypoglycemia)  
  • Delayed growth and development  
  • Mental-motor retardation

Calling your health care provider

Call your health care provider if you are pregnant and believe you are going into labor prematurely.

If you are pregnant, and not receiving prenatal care, call your health care provider or the State Department of Health. Most Health Departments have programs to ensure that pregnant mothers, whether covered by insurance or not, able to pay or not, receive adequate prenatal care. They will direct you to the appropriate provider.


One of the most important steps to preventing prematurity is to begin prenatal care as early as possible and to continue prenatal care throughout the pregnancy. This cannot be stressed enough.

Statistics clearly show that early and good prenatal care reduces the chance of a premature birth, having a small baby, and related deaths during delivery and the neonatal period.

Premature labor can sometimes be treated or delayed by a medication that inhibits uterine contractions. Many times, however, attempts to inhibit premature labor are not successful and thus a “cure” for prematurity remains elusive.

Johns Hopkins patient information

Last revised: December 5, 2012
by David A. Scott, M.D.

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