Definition of Premature infant:

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

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.

Health conditions and events in the mother may contribute to preterm labor. Examples are:

• Diabetes
• Heart disease
• Infection (such as a urinary tract infection or infection of the amniotic membrane)
• Kidney disease

Different pregnancy-related problems increase the risk of preterm labor:

• An "insufficient" or weakened cervix, also called cervical incompetence
• Birth defects of the uterus
• History of preterm delivery
• Poor nutrition right before or during pregnancy
• Preeclampsia -- the development of high blood pressure and protein in the urine after the 20th week of pregnancy
• Premature rupture of the membranes (placenta previa)

Other factors that make preterm labor and a premature delivery more likely include:

• African-American ethnicity (not related to socioeconomic status)
• Age (younger than 16 or older than 35)
• Lack of prenatal care
• Low socioeconomic status
• Use of tobacco, cocaine, or amphetamines