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premature birth
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premature infant in NICU with wires taped onto their chest and face and a ventilator in the corner Premature birth birth: premature birth: premature
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premature infant in NICU with wires taped onto their chest and face and a ventilator in the corner
NICUs, the birth of neonatology A premature infant receiving treatment in a neonatal intensive care unit.

premature birth

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premature birth, in humans, any birth that occurs less than 37 weeks after conception. A full-term pregnancy lasts anywhere from 37 to 42 weeks.

The worldwide incidence of premature birth ranges between 6 and 11 percent. In the United States the rate of premature birth was 10.4 percent in 2022; that rate varied across racial and ethnic lines, with prematurity in 9.4 percent of pregnancies in white women, 14.6 percent in African American women, and 10.1 percent in Hispanic women, according to the Centers for Disease Control and Prevention. About 40 to 60 percent of premature births can be attributed to conditions such as multiple pregnancy, preeclampsia (maternal pregnancy-induced hypertension), abnormal attachment of the placenta, or congenital malformation of the infant. Poor maternal health, hygiene, and nutrition increase the likelihood of prematurity; maternal accidents and acute illness are insignificant as causes. Genetics may play a role as well. For example, variations (polymorphisms) in a gene known as FSHR (follicle stimulating hormone receptor) are thought to be associated with premature birth.

Increased research associated with the advent of neonatology has brought better outcomes for premature infants. One key advancement was the creation of the modern neonatal intensive care unit (NICU), credited to Mildred Stahlman, which provides specialized care for critically ill or premature infants. The chief specific causes of death among premature infants are respiratory disturbances, infections, and spontaneous hemorrhages, especially into the brain or lungs. With good care, about 85 percent of all live-born premature infants should survive; those of higher weight have a better chance. Individuals born prematurely tend to be at increased risk of certain health conditions later in life, however, including asthma, cardiovascular disease, and infections.

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Premature birth
Premature birthA premature baby with oxygen in a hospital neonatal intensive care unit.

Prematurity is to be distinguished from intrauterine growth retardation, in which weight and development are subnormal for fetal age. An estimated 1.5 to 2 percent of all babies are significantly below a birth weight proper to their fetal age. Deficiency of transplacental nutrition from various causes is frequently responsible. Other causes include fetal infections and some malformations. Generally, babies under 5.5 pounds but carried for more than 37 weeks are considered growth-retarded rather than premature.

The Editors of Encyclopaedia BritannicaThis article was most recently revised and updated by Virginia Hunt.