Changes in the gestational age distribution among U.S. singleton births: Impact on rates of late preterm birth, 1992 to 2002

Michael J. Davidoff, Todd Dias, Karla Damus, Rebecca Russell, Vani R. Bettegowda, Siobhan Dolan, Richard H. Schwarz, Nancy S. Green, Joann Petrini

Research output: Contribution to journalArticle

401 Scopus citations


There is mounting evidence that infants born late preterm (34-36 weeks) are at greater risk for morbidity than term infants. This article examines the changing epidemiology of gestational length among singleton births in the United States, from 1992 to 2002. Analyzing gestational age by mode of delivery, the distribution of spontaneous births shifted to the left, with 39 weeks becoming the most common length of gestation in 2002, compared with 40 weeks in 1992 (P < 0.001). Deliveries at ≥40 weeks gestation markedly decreased, accompanied by an increase in those at 34 to 39 weeks (P < 0.001). Singleton births with PROM or medical interventions had similar trends. Changes in the distribution of all singleton births differed by race/ethnicity, with non-Hispanic white infants having the largest increase in late preterm births. These observations, in addition to emerging evidence of increased morbidity, suggest the need for investigation of optimal obstetric and neonatal management of these late preterm infants.

Original languageEnglish (US)
Pages (from-to)8-15
Number of pages8
JournalSeminars in Perinatology
Issue number1
Publication statusPublished - Feb 2006



  • Cesarean section
  • Duration of pregnancy
  • Gestational age
  • Labor induction
  • Late preterm
  • Premature rupture of the membranes
  • Prematurity

ASJC Scopus subject areas

  • Pediatrics, Perinatology, and Child Health
  • Obstetrics and Gynecology

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