title: Placenta previa and the risk of preterm delivery.
abstract: OBJECTIVE
  We aimed to quantify the risk of preterm delivery and maternal and neonatal morbidities associated with placenta previa.
  
  
  METHODS
  We conducted a retrospective cohort study of singleton births that occurred between 1976 and 2001, examining outcomes including preterm delivery and perinatal complications. Multivariate logistic regression was used to control for potential confounders. Kaplan-Meier survival curves were constructed to compare preterm delivery in pregnancies complicated by previa vs. no previa.
  
  
  RESULTS
  Among the 38 540 women, 230 women had previas (0.6%). Compared to controls, pregnancies with previa were significantly associated with preterm delivery prior to 28 weeks (3.5% vs. 1.3%; p = 0.003), 32 weeks (11.7% vs. 2.5%; p < 0.001), and 34 weeks (16.1% vs. 3.0%; p < 0.001) of gestation. Patients with previa were more likely to be diagnosed with postpartum hemorrhage (59.7% vs. 17.3%; p < 0.001) and to receive a blood transfusion (11.8% vs. 1.1%; p < 0.001). Survival curves demonstrate the risk of preterm delivery at each week and showed an overall higher rate of preterm delivery for patients with a placenta previa.
  
  
  CONCLUSIONS
  Placenta previa is associated with maternal and neonatal complications, including preterm delivery and postpartum hemorrhage. These specific outcomes can be used to counsel women with previa.
authors.affiliation: Department of Obstetrics, Gynecology and Reproductive Sciences, University of California San Francisco, San Francisco, California 94143, USA. zlatnikm@obgyn.ucsf.edu
authors.forename: Marya G
authors.initials: MG
authors.lastname: Zlatnik
authors.forename: Yvonne W
authors.initials: YW
authors.lastname: Cheng
authors.forename: Mary E
authors.initials: ME
authors.lastname: Norton
authors.forename: Mari-Paule
authors.initials: MP
authors.lastname: Thiet
authors.forename: Aaron B
authors.initials: AB
authors.lastname: Caughey
mesh_terms: D000328:Adult; D000367:Age Factors; D015331:Cohort Studies; D005260:Female; D005865:Gestational Age; D006801:Humans; D007230:Infant, Low Birth Weight; D007231:Infant, Newborn; D007567:Jaundice, Neonatal; D053208:Kaplan-Meier Estimate; D008423:Maternal Age; D010298:Parity; D010923:Placenta Previa; D006473:Postpartum Hemorrhage; D011247:Pregnancy; D047928:Premature Birth / Q000453:epidemiology*; D012127:Respiratory Distress Syndrome, Newborn; D012189:Retrospective Studies; D012307:Risk Factors