title: Risk factors for retained placenta.
abstract: OBJECTIVE
  Retained placenta complicates 2-3% of vaginal deliveries and is a known cause of postpartum hemorrhage. Treatment includes manual or operative placental extraction, potentially increasing risks of hemorrhage, infections, and prolonged hospital stays. We sought to evaluate risk factors for retained placenta, defined as more than 30 minutes between the delivery of the fetus and placenta, in a large US obstetrical cohort.
  
  
  METHODS
  We included singleton, vaginal deliveries ≥24 weeks (n = 91,291) from the Consortium of Safe Labor from 12 US institutions (2002-2008). Multivariable logistic regression analyses estimated the adjusted odds ratios (OR) and 95% confidence intervals (CI) for potential risk factors for retained placenta stratified by parity, adjusting for relevant confounding factors. Characteristics such as stillbirth, maternal age, race, and admission body mass index were examined.
  
  
  RESULTS
  Retained placenta complicated 1047 vaginal deliveries (1.12%). Regardless of parity, significant predictors of retained placenta included stillbirth (nulliparous adjusted OR, 5.67; 95% CI, 3.10-10.37; multiparous adjusted OR, 4.56; 95% CI, 2.08-9.94), maternal age ≥30 years, delivery at 24 0/7 to 27 6/7 compared with 34 weeks or later and delivery in a teaching hospital. In nulliparous women, additional risk factors were identified: longer first- or second-stage labor duration, whereas non-Hispanic black compared with non-Hispanic white race was found to be protective. Body mass index was not associated with an increased risk.
  
  
  CONCLUSIONS
  Multiple risk factors for retained placenta were identified, particularly the strong association with stillbirth. It is plausible that there could be something intrinsic about stillbirth that causes a retained placenta, or perhaps there are shared pathways of certain etiologies of stillbirth and a risk of retained placenta.
authors.affiliation: Department of Obstetrics and Gynecology, MedStar Washington Hospital Center, MedStar Georgetown University Hospital, Washington, DC; Department of Obstetrics and Gynecology, MedStar Georgetown University Hospital, Washington, DC. Electronic address: Elizabeth.coviello@gmail.com.
authors.forename: Elizabeth M
authors.initials: EM
authors.lastname: Coviello
authors.affiliation: Department of Obstetrics and Gynecology, MedStar Georgetown University Hospital, Washington, DC.
authors.forename: Katherine L
authors.initials: KL
authors.lastname: Grantz
authors.affiliation: Department of Biostatistics and Bioinformatics, MedStar Health Research Institute, Hyattsville, MD.
authors.forename: Chun-Chih
authors.initials: CC
authors.lastname: Huang
authors.affiliation: Department of Obstetrics and Gynecology, MedStar Georgetown University Hospital, Washington, DC.
authors.forename: Tara E
authors.initials: TE
authors.lastname: Kelly
authors.affiliation: Department of Obstetrics and Gynecology, MedStar Georgetown University Hospital, Washington, DC; Division of Maternal Fetal Medicine, MedStar Georgetown University Hospital, Washington, DC.
authors.forename: Helain J
authors.initials: HJ
authors.lastname: Landy
mesh_terms: D000328:Adult; D015331:Cohort Studies; D016208:Databases, Factual; D005260:Female; D006784:Hospitals, Teaching; D006801:Humans; D007747:Labor Stage, First; D007748:Labor Stage, Second; D008423:Maternal Age; D015999:Multivariate Analysis; D010298:Parity; D018457:Placenta, Retained / Q000453:epidemiology*; D006473:Postpartum Hemorrhage / Q000453:epidemiology; D011247:Pregnancy; D047928:Premature Birth; D012189:Retrospective Studies; D012307:Risk Factors; D050497:Stillbirth / Q000453:epidemiology; D013997:Time Factors; D014481:United States / Q000453:epidemiology
keywords: postpartum hemorrhage; preterm birth; retained placenta; stillbirth