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Late preterm infants

Wanda D Barfield, MD, MPH, FAAP
Kimberly G Lee, MD, MS, IBCLC
Section Editor
Leonard E Weisman, MD
Deputy Editor
Melanie S Kim, MD


Late preterm infants are born at a gestational age (GA) between 34 weeks and 0 days, and 36 weeks and 6 days. They have higher morbidity and mortality rates than term infants (gestational age ≥37 weeks) due to their relative physiologic and metabolic immaturity, even though they are often the size and weight of some term infants.

The epidemiology, outcomes, and management of late preterm infants will be reviewed here.

The views reported in this article are those of the author and do not necessarily represent the official position of the Centers for Disease Control and Prevention (CDC).


It is well established that gestational age has a major impact upon clinical outcome. Thus, it is necessary to standardize medical terminology related to neonatal maturation by gestational age rather than birth weight so that gestational age-appropriate care can be administered, and data from different studies can be compared.

Preterm birth – The World Health Organization (WHO), the American Academy of Pediatrics (AAP), and the American College of Obstetricians and Gynecologists (ACOG) define preterm birth as the delivery of an infant before completion of 37 weeks gestation. This occurs on or before the 259th day after the first day of the last menstrual period (LMP) of the mother.

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Literature review current through: Nov 2017. | This topic last updated: Oct 20, 2017.
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