Premature infant

Alternative names:

prematurity, premie; preterm infant

Definition:

Any infant born before 37 weeks gestation.

Causes, incidence, and risk factors:

Each newborn is classified at birth as premature (less than 37 weeks gestation), full-term (37 to 42 weeks gestation), or postmature (born after 42 weeks gestation). Often, the cause of premature labor, or premature rupture of the membranes followed by premature labor, is unknown. 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 mellitus, infection, or heart disease may also contribute to preterm labor. Multiple pregnancy (the presence of more than one fetus in the uterus) accounts for 15 percent of all premature births.

The problems of premature infants are related to the immaturity of their organ systems. The infant requires specialized care in a nursery until its 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; and kidney immaturity.

Risk factors that may contribute to preterm labor include: adolescent pregnancy (less than 18 years), lack of prenatal care, low socioeconomic status, poor nutrition, poor education and substance abuse. Problems inherent to the mother's health include: a history of a previous pre-term deliver, 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 cervical incompetence, premature rupture of the membranes or placenta previa. Approximately 10 percent of all births in the U.S. occur before 37 weeks gestation.