title: Variation in labor induction over the days of the week.
abstract: OBJECTIVE
  To quantify the variation in induction of labor (IOL) over the days of the week for gravid women in the United States.
  
  
  METHODS
  Women who delivered singletons between 24 and 42 weeks' gestation were identified using birth certificate data from 2007 to 2010. Women with pregnancy-associated hypertension, fetal anomalies, previous cesarean delivery, or incomplete records were excluded. The primary outcome was IOL. Women were stratified into four gestational age groups: < 34, 34 to 36, 37 to 38, and ≥ 39 weeks. Frequencies of IOL were determined according to day of the week. Multivariable logistic regression estimated the association between weekend delivery and IOL, adjusting for maternal characteristics and year of delivery.
  
  
  RESULTS
  There were 11.6 million eligible women. For each gestational age stratum, the frequency of IOL was increased on weekdays compared with weekends (8.0 vs. 7.4%, 16.5 vs. 13.2%, 25.0 vs. 14.8%, and 33.2 vs. 19.3% at < 34, 34-36, 37-38, and ≥ 39 weeks, respectively; p < 0.01 for all). Multivariable analyses demonstrated that weekend IOL was inversely related to gestational age (odds ratios: 0.93, 0.77, 0.52, and 0.48, respectively; p < 0.001 for all).
  
  
  CONCLUSIONS
  The frequency of IOL varies according to the day of the week, with the odds of weekend IOL lowest at greater gestational ages.
authors.affiliation: Division of Neonatology, Department of Pediatrics, Ann & Robert H. Lurie Children's Hospital of Chicago, Northwestern University, Chicago, Illinois.
authors.forename: Gustave H
authors.initials: GH
authors.lastname: Falciglia
authors.affiliation: Division of Maternal-Fetal Medicine, Department of Obstetrics and Gynecology, Prentice Women's Hospital-Northwestern Memorial Hospital, Northwestern University, Chicago, Illinois.
authors.forename: William A
authors.initials: WA
authors.lastname: Grobman
authors.affiliation: Division of Neonatology, Department of Pediatrics, Ann & Robert H. Lurie Children's Hospital of Chicago, Northwestern University, Chicago, Illinois.
authors.forename: Karna
authors.initials: K
authors.lastname: Murthy
mesh_terms: D000293:Adolescent; D000328:Adult; D005260:Female; D005865:Gestational Age; D006801:Humans; D006973:Hypertension / Q000453:epidemiology*; D007751:Labor, Induced / Q000706:statistics & numerical data*; D016015:Logistic Models; D015999:Multivariate Analysis; D011247:Pregnancy; D011249:Pregnancy Complications, Cardiovascular / Q000453:epidemiology*; D011254:Pregnancy in Diabetics / Q000453:epidemiology*; D012189:Retrospective Studies; D012307:Risk Factors; D013997:Time Factors; D014481:United States; D055815:Young Adult