title: Predicting the route of delivery in women with low-lying placenta using transvaginal ultrasonography: significance of placental migration and marginal sinus.
abstract: OBJECTIVE
  To examine the significance of placental migration and the presence of a placental marginal sinus to predict the eventual route of delivery in low-lying placenta.
  
  
  METHODS
  49 women with a low-lying placenta after 30 weeks' gestation were studied. The distance between the internal os and leading edge of the placenta was measured weekly using transvaginal ultrasonography until 37 weeks' gestation. The relationship between the rate of placental migration, the presence of a placental marginal sinus and the eventual mode of delivery was investigated.
  
  
  RESULTS
  Although the cesarean section rate was 56.3% (9/16) in the 'slow' migration (0-2.0 mm/week) group, no patient (0/33) in the 'fast' (>2.0 mm/week) migration group underwent a cesarean section (p < 0.01). The cesarean section rate was 71.4% (5/7) in patients with a placental marginal sinus, significantly greater than the rate of 9.5% (4/42) in patients without a marginal sinus (p < 0.01).
  
  
  CONCLUSIONS
  A decreased rate of placental migration until 37 weeks' gestation and the presence of a placental marginal sinus were associated with subsequent cesarean delivery because of antepartum vaginal bleeding. These parameters may be useful for predicting the route of delivery in women with a low-lying placenta.
authors.affiliation: Department of Obstetrics and Gynecology, Shinshu University School of Medicine, 3-1-1 Asahi, Matsumoto, Japan.
authors.forename: Satoshi
authors.initials: S
authors.lastname: Ohira
authors.forename: Norihiko
authors.initials: N
authors.lastname: Kikuchi
authors.forename: Hisanori
authors.initials: H
authors.lastname: Kobara
authors.forename: Ryosuke
authors.initials: R
authors.lastname: Osada
authors.forename: Takashi
authors.initials: T
authors.lastname: Ashida
authors.forename: Makoto
authors.initials: M
authors.lastname: Kanai
authors.forename: Tanri
authors.initials: T
authors.lastname: Shiozawa
mesh_terms: D000328:Adult; D002585:Cesarean Section / Q000706:statistics & numerical data; D036861:Delivery, Obstetric / Q000379:methods*; D019160:Endosonography; D005260:Female; D006801:Humans; D010920:Placenta / Q000000981:diagnostic imaging; D010923:Placenta Previa / Q000000981:diagnostic imaging*; D011237:Predictive Value of Tests; D011247:Pregnancy; D011263:Pregnancy Trimester, Third; D012189:Retrospective Studies; D016216:Ultrasonography, Prenatal