title: Type and location of placenta previa affect preterm delivery risk related to antepartum hemorrhage.
abstract: OBJECTIVE
  To evaluate whether type and location of placenta previa affect risk of antepartum hemorrhage-related preterm delivery.
  
  
  METHODS
  We retrospectively studied 162 women with singleton pregnancies presenting placenta previa. Through observation using transvaginal ultrasound the women were categorized into complete or incomplete placenta previa, and then assigned to anterior and posterior groups. Complete placenta previa was defined as a placenta that completely covered the internal cervical os, with the placental margin >2 cm from the os. Incomplete placenta previa comprised marginal placenta previa whose margin adjacent to the internal os and partial placenta previa which covered the os but the margin situated within 2 cm of the os. Maternal characteristics and perinatal outcomes in complete and incomplete placenta previa were compared, and the differences between the anterior and the posterior groups were evaluated.
  
  
  RESULTS
  Antepartum hemorrhage was more prevalent in women with complete placenta previa than in those with incomplete placenta previa (59.1% versus 17.6%), resulting in the higher incidence of preterm delivery in women with complete than in those with incomplete placenta previa [45.1% versus 8.8%; odds ratio (OR) 8.51; 95% confidence interval (CI) 3.59-20.18; p < 0.001]. In complete placenta previa, incidence of antepartum hemorrhage did not significantly differ between the anterior and the posterior groups. However, gestational age at bleeding onset was lower in the anterior group than in the posterior group, and the incidence of preterm delivery was higher in the anterior group than in the posterior group (76.2% versus 32.0%; OR 6.8; 95% CI 2.12-21.84; p = 0.002). In incomplete placenta previa, gestational age at delivery did not significantly differ between the anterior and posterior groups.
  
  
  CONCLUSIONS
  Obstetricians should be aware of the increased risk of preterm delivery related to antepartum hemorrhage in women with complete placenta previa, particularly when the placenta is located on the anterior wall.
authors.affiliation: Department of Obstetrics and Gynecology, Nippon Medical School, Tokyo, Japan.
authors.forename: Atsuko
authors.initials: A
authors.lastname: Sekiguchi
authors.forename: Akihito
authors.initials: A
authors.lastname: Nakai
authors.forename: Ikuno
authors.initials: I
authors.lastname: Kawabata
authors.forename: Masako
authors.initials: M
authors.lastname: Hayashi
authors.forename: Toshiyuki
authors.initials: T
authors.lastname: Takeshita
mesh_terms: D000328:Adult; D015148:Cardiotocography; D002585:Cesarean Section; D005260:Female; D005865:Gestational Age; D006801:Humans; D007231:Infant, Newborn; D010920:Placenta / Q000473:pathology*; D010923:Placenta Previa / Q000473:pathology*; D011247:Pregnancy; D011248:Pregnancy Complications; D047928:Premature Birth / Q000209:etiology / Q000473:pathology*; D012307:Risk Factors; D016216:Ultrasonography, Prenatal; D014592:Uterine Hemorrhage / Q000150:complications / Q000473:pathology
keywords: antepartum hemorrhage.; anterior placenta previa; complete placenta previa; preterm delivery