title: Respiratory morbidity in late preterm births.
abstract: BACKGROUND
  Late preterm births (340/7-366/7 weeks) account for an increasing proportion of prematurity-associated short-term morbidities, particularly respiratory, that require specialized care and prolonged neonatal hospital stays.
  
  
  OBJECTIVE
  To assess short-term respiratory morbidity in late preterm births compared with term births in a contemporary cohort of deliveries in the United States.
  
  
  METHODS
  Retrospective collection of electronic data from 12 institutions (19 hospitals) across the United States on 233,844 deliveries between 2002 and 2008. Charts were abstracted for all neonates with respiratory compromise admitted to a neonatal intensive care unit (NICU), and late preterm births were compared with term births in regard to resuscitation, respiratory support, and respiratory diagnoses. A multivariate logistic regression analysis compared infants at each gestational week, controlling for factors that influence respiratory outcomes.
  
  
  METHODS
  Respiratory distress syndrome, transient tachypnea of the newborn, pneumonia, respiratory failure, and standard and oscillatory ventilator support.
  
  
  RESULTS
  Of 19,334 late preterm births, 7055 (36.5%) were admitted to a NICU and 2032 had respiratory compromise. Of 165,993 term infants, 11,980 (7.2%) were admitted to a NICU, 1874 with respiratory morbidity. The incidence of respiratory distress syndrome was 10.5% (390/3700) for infants born at 34 weeks' gestation vs 0.3% (140/41,764) at 38 weeks. Similarly, incidence of transient tachypnea of the newborn was 6.4% (n = 236) for those born at 34 weeks vs 0.4% (n = 155) at 38 weeks, pneumonia was 1.5% (n = 55) vs 0.1% (n = 62), and respiratory failure was 1.6% (n = 61) vs 0.2% (n = 63). Standard and oscillatory ventilator support had similar patterns. Odds of respiratory distress syndrome decreased with each advancing week of gestation until 38 weeks compared with 39 to 40 weeks (adjusted odds ratio [OR] at 34 weeks, 40.1; 95% confidence interval [CI], 32.0-50.3 and at 38 weeks, 1.1; 95% CI, 0.9-1.4). At 37 weeks, odds of respiratory distress syndrome were greater than at 39 to 40 weeks (adjusted OR, 3.1; 95% CI, 2.5-3.7), but the odds at 38 weeks did not differ from 39 to 40 weeks. Similar patterns were noted for transient tachypnea of the newborn (adjusted OR at 34 weeks, 14.7; 95% CI, 11.7-18.4 and at 38 weeks, 1.0; 95% CI, 0.8-1.2), pneumonia (adjusted OR at 34 weeks, 7.6; 95% CI, 5.2-11.2 and at 38 weeks, 0.9; 95% CI, 0.6-1.2), and respiratory failure (adjusted OR at 34 weeks, 10.5; 95% CI, 6.9-16.1 and at 38 weeks, 1.4; 95% CI, 1.0-1.9).
  
  
  CONCLUSIONS
  In a contemporary cohort, late preterm birth, compared with term delivery, was associated with increased risk of respiratory distress syndrome and other respiratory morbidity.
authors.forename: Judith U
authors.initials: JU
authors.lastname: Hibbard
authors.forename: Isabelle
authors.initials: I
authors.lastname: Wilkins
authors.forename: Liping
authors.initials: L
authors.lastname: Sun
authors.forename: Kimberly
authors.initials: K
authors.lastname: Gregory
authors.forename: Shoshana
authors.initials: S
authors.lastname: Haberman
authors.forename: Matthew
authors.initials: M
authors.lastname: Hoffman
authors.forename: Michelle A
authors.initials: MA
authors.lastname: Kominiarek
authors.forename: Uma
authors.initials: U
authors.lastname: Reddy
authors.forename: Jennifer
authors.initials: J
authors.lastname: Bailit
authors.forename: D Ware
authors.initials: DW
authors.lastname: Branch
authors.forename: Ronald
authors.initials: R
authors.lastname: Burkman
authors.forename: Victor Hugo
authors.initials: VH
authors.lastname: Gonzalez Quintero
authors.forename: Christos G
authors.initials: CG
authors.lastname: Hatjis
authors.forename: Helain
authors.initials: H
authors.lastname: Landy
authors.forename: Mildred
authors.initials: M
authors.lastname: Ramirez
authors.forename: Paul
authors.initials: P
authors.lastname: VanVeldhuisen
authors.forename: James
authors.initials: J
authors.lastname: Troendle
authors.forename: Jun
authors.initials: J
authors.lastname: Zhang
mesh_terms: D000368:Aged; D005260:Female; D006801:Humans; D015994:Incidence; D007231:Infant, Newborn; D007234:Infant, Premature; D007235:Infant, Premature, Diseases / Q000453:epidemiology*; D008171:Lung Diseases / Q000453:epidemiology*; D008297:Male; D009017:Morbidity; D047928:Premature Birth; D012121:Respiration, Artificial / Q000706:statistics & numerical data; D012189:Retrospective Studies; D014481:United States / Q000453:epidemiology