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Age of viability

Definition:
The age at which a premature baby can survive outside of the uterus.
 
Background:
The age of viability occurs sometime between 22 and 26 weeks, usually when the weight is greater than 500 grams. The probability of survival is slim at 22-23 weeks, but increases to approximately 85% at 26-28 weeks. Respiratory problems are the most common complications that a preterm infant experiences. Failure to breathe normally may be due to immaturity, anoxia at birth (lack of oxygen), hemorrhage or drug-induced respiratory depression.
 
Further Reading:

Gabbe, S. G., Niebyl, J. R., & Simpson, J. L. (Eds.) (1991). Obstetrics: Normal and problems pregnancies. New York: Churchill Livingstone.

Rigatto, H., & Brady, J.P (1972). Periodic breathing and apnea in preterm infants II. Hypoxia as a primary event. Pediatrics. 50, 219.

 
Related Terms:
Fetal stage

Infant mortality

Self-Instructional Resources:
Take a 2-item self-test over this concept.

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