Definition

A premature infant is a baby born before 37 weeks gestation.

Alternative Names

Preterm infant; Preemie

Causes, incidence, and risk factors

At birth, a baby is classified as one of the following:

• Premature (less than 37 weeks gestation)
• Full term (37 to 42 weeks gestation)
• Post term (born after 42 weeks gestation)

If a woman goes into labor before 37 weeks, it is called preterm labor. Often, the cause of preterm labor is unknown. Multiple pregnancy (twins, triplets, etc.) makes up about 15% of all premature births.

The following health conditions and events in the mother may contribute to preterm labor:

• Diabetes
• Heart disease
• Infection
• Kidney disease
• Lack of prenatal care
• Poor nutrition
• Preeclampsia --the development of high blood pressure and protein in the urine after the 20th week of pregnancy
• Substance abuse
• Young age (a mother age younger than 18)

A woman who has had any of the following is at increase risk of preterm labor:

• Premature rupture of the membranes or placenta previa
• Previous preterm delivery
• Problems with the uterus or cervix
• Unexplained high alpha-fetoprotein level in the second trimester
• Untreated disease or infection (such as urinary tract infection or infection of the amniotic membranes)

Symptoms

A premature infant has organs that are not fully developed. The infant needs special care in a nursery until the organ systems have developed enough to sustain life without medical support. This may take weeks to months.

A premature infant will have a low birth weight. Common symptoms in a premature infant include:

• Body hair
• Episodes of absent breathing
• Enlarged clitoris (female infant)
• Lung problems such as neonatal respiratory distress syndrome
• Poor feeding
• Small scrotum, smooth without ridges (male infant)
• Soft, flexible ear cartilage
• Thin, smooth, shiny skin
• Transparent skin (can see veins under skin)
• Usually inactive -- however, may be unusually active immediately after birth
• Weak cry
• Wrinkled features

This list may not be all inclusive.

Signs and tests

The infant may have a low body temperature and show signs of breathing problems.

Common tests performed on a premature infant include:

• Blood gas analysis
• Blood tests to check glucose, calcium, and bilirubin levels
• Chest x-ray

Reviewer Info: Deirdre O?Reilly, MD, MPH, Neonatologist, Division of Newborn Medicine, Children?s Hospital Boston and Instructor in Pediatrics, Harvard Medical School, Boston, Massachusetts. Review Provided by VeriMed Healthcare Network., 10/11/2007