Premature Infant

What is prematurity?

A baby born before 37 weeks of pregnancy is considered premature, that is, born before complete maturity. Slightly fewer than 12 percent of all babies are premature. Overall, the rate of premature births is rising, mainly due to the large numbers of multiple births in recent years. Twins and other multiples are about six times more likely to be premature than single birth babies. The rate of premature single births is also slightly increasing each year.

According to the National Center for Health Statistics for 2011, 12 percent of babies born in the U.S. are born preterm, or before 37 completed weeks of pregnancy. Of all babies:

  • About 8 percent are born between 34 and 36 weeks of gestation (the time from conception to birth)
  • About 1.5 percent are born between 32 and 33 weeks of gestation
  • About 2 percent are born under 32 weeks of gestation

Other terms often used for prematurity are preterm and "preemie." Many premature babies also weigh less than 2,500 grams (5 lbs 8 oz) and may be referred to as low birthweight (LBW).

Premature infants born between 34 and 37 weeks of pregnancy are often called late preterm or near-term infants. Late preterm infants are often much larger than very premature infants but may only be slightly smaller than full-term infants.

Late preterm babies usually appear healthy at birth but may have more difficulties adapting than full-term babies. Because of their smaller size, they may have trouble maintaining their body temperature. They often have difficulty with breastfeeding and bottle feeding, and may need to eat more frequently. They usually require more sleep and may even sleep through a feeding, which means they miss much-needed calories.

Late preterm infants may also have breathing difficulties, although these are often identified before the infants go home from the hospital. These infants are also at higher risk for infections and jaundice, and should be watched for signs of these conditions. Late preterm infants should be seen by a care provider within the first one or two days after going home from the hospital.

Prevention & Risk Treatment

Prevention & Risk Treatment

What causes prematurity?

There are many factors linked to premature birth. Some directly cause early labor and birth, while others can make the mother or baby sick and require early delivery. The following factors may contribute to a premature birth:

  • Maternal factors:
    • Preeclampsia (high blood pressure of pregnancy, also known as toxemia or gestational hypertension)
    • Chronic medical illness (such as heart or kidney disease)
    • Infection (such as group B streptococcus, urinary tract infections, vaginal infections, infections of the fetal/placental tissues)
    • Drug use (such as cocaine)
    • Abnormal structure of the uterus
    • Cervical incompetence (inability of the cervix to stay closed during pregnancy)
    • Previous preterm birth
  • Factors involving the pregnancy:
    • Abnormal or decreased function of the placenta
    • Placenta previa (low lying position of the placenta)
    • Placental abruption (early detachment from the uterus)
    • Premature rupture of membranes (amniotic sac)
    • Polyhydramnios (too much amniotic fluid)
  • Factors involving the fetus:
    • When fetal behavior indicates the intrauterine environment is not healthy
    • Multiple gestation (twins, triplets or more)

Why is prematurity a concern?

Premature babies are born before their bodies and organ systems have completely matured. These babies are often small, with low birthweight (less than 2,500 grams or 5 lbs 8 oz), and they may need help breathing, eating, fighting infection, and staying warm. Very premature babies, those born before 28 weeks, are especially vulnerable. Many of their organs may not be ready for life outside the mother's uterus and may be too immature to function well.

Some of the problems premature babies may experience include:

  • Temperature instability - inability to stay warm due to low body fat.
  • Respiratory problems:
    • Infant respiratory distress syndrome (previously called hyaline membrane disease). A condition in which the air sacs cannot stay open due to lack of surfactant in the lungs.
    • Chronic lung disease/bronchopulmonary dysplasia. These are long-term respiratory problems caused by injury to the lung tissue.
    • Air leaking out of the normal lung spaces into other tissues
    • Incomplete lung development
    • Apnea (stopping breathing). This occurs in about half of babies born at or before 30 weeks.
  • Cardiovascular:
    • Patent ductus arteriosus (PDA). A heart condition that causes blood to divert away from the lungs.
    • Too low or too high blood pressure
    • Low heart rate. This often occurs with apnea.
  • Blood and metabolic:
    • Anemia. This may require blood transfusion.
    • Jaundice. This is due to immaturity of liver and gastrointestinal function.
    • Too low or too high levels of minerals and other substances in the blood, such as calcium and glucose (sugar)
    • Immature kidney function
  • Gastrointestinal:
    • Difficulty feeding. Many premature babies are unable to coordinate suck and swallow before 35 weeks gestation.
    • Poor digestion
    • Necrotizing enterocolitis (NEC). A serious disease of the intestine common in premature babies.
  • Neurologic:
    • Intraventricular hemorrhage. This is bleeding in the brain.
    • Periventricular leukomalacia. A softening of tissues of the brain around the ventricles (the spaces in the brain containing cerebrospinal fluid).
    • Poor muscle tone
    • Seizures. These may be due to bleeding in the brain.
    • Retinopathy of prematurity. This is abnormal growth of the blood vessels in a baby's eye.
  • Infections. Premature infants are more susceptible to infection and may require antibiotics. Premature babies can have long-term health problems as well. Generally, the more premature the baby, the more serious and long-lasting are the health problems.

Prevention of prematurity

Because of the tremendous advances in the care of sick and premature babies, more and more babies are surviving despite being born early and being very small. But prevention of early birth is the best way of promoting good health for babies.

Prenatal care is a key factor in preventing preterm births and low birthweight babies. At prenatal visits, the health of both mother and fetus can be checked. Because maternal nutrition and weight gain are linked with fetal weight gain and birthweight, eating a healthy diet and gaining weight in pregnancy are essential. Prenatal care is also important in identifying problems and lifestyles that can increase the risks for preterm labor and birth. Some ways to help prevent prematurity and to provide the best care for premature babies may include the following:

  • Identifying mothers at risk for preterm labor
  • Prenatal education of the symptoms of preterm labor
  • Avoiding heavy or repetitive work or standing for long periods of time that can increase the risk of preterm labor
  • Early identification and treatment of preterm labor


What are the characteristics of prematurity?

The following are the most common characteristics of a premature baby. However, each baby may show different characteristics of the condition. Characteristics may include:

  • Small baby, often weighing less than 2,500 grams (5 lbs 8 oz)
  • Thin, shiny, pink or red skin, able to see veins
  • Little body fat
  • Little scalp hair, but may have lots of lanugo (soft body hair)
  • Weak cry and body tone
  • Genitals may be small and underdeveloped

The characteristics of prematurity may resemble other conditions or medical problems. Always consult your baby's doctor for a diagnosis.

Children's Team

Children's Team


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Primary Care
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Primary Care

An Massaro


Pediatric Residency Assistant Program Director, Director of Residency Research




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