title: Placenta previa with early opening of the uterine isthmus is associated with high risk of bleeding during pregnancy, and massive haemorrhage during caesarean delivery.
abstract: OBJECTIVE
  To demonstrate the relationship between the timing of opening of the uterine isthmus and bleeding during pregnancy and caesarean section in patients with placenta previa.
  
  
  METHODS
  A prospective observational study was conducted at a single perinatal centre. All patients with placenta previa, diagnosed between 20 and 22 weeks of gestation, who were followed up at the study hospital and underwent caesarean section were enrolled. The condition of the uterine isthmus was examined every 2 weeks. The timing (in gestational weeks) of complete opening of the uterine isthmus was determined. Patients were divided into two groups: patients in whom the uterine isthmus opened before 25 weeks of gestation (EO-previa), and patients in whom the uterine isthmus opened after 25 weeks of gestation (LO-previa). The frequency of bleeding during pregnancy and the amount of intra-operative bleeding were compared between the two groups.
  
  
  RESULTS
  Forty-four cases of EO-previa and 55 cases of LO-previa were analysed. Complete placenta previa at delivery was observed more frequently in the EO-previa group than in the LO-previa group (88.6% vs 47.3%, p<0.001). An emergency caesarean section due to active bleeding was performed more frequently in the EO-previa group (48%) than in the LO-previa group (25%) (p=0.021). The frequency of massive haemorrage (>2500ml) during caesarean section was higher in the EO-previa group than in the LO-previa group (25% vs 9%, p=0.033).
  
  
  CONCLUSIONS
  Placenta previa was associated with a high risk of bleeding leading to emergency caesarean section during pregnancy, and massive haemorrhage during caesarean section in patients in whom the uterine isthmus opened before 25 weeks of gestation.
authors.affiliation: Department of Obstetrics and Gynaecology, Showa University School of Medicine, Tokyo, Japan.
authors.forename: M
authors.initials: M
authors.lastname: Goto
authors.affiliation: Department of Obstetrics and Gynaecology, Showa University School of Medicine, Tokyo, Japan; Department of Obstetrics and Gynaecology, St. Marianna University School of Medicine, Kanagawa, Japan. Electronic address: hasejun@oak.dti.ne.jp.
authors.forename: J
authors.initials: J
authors.lastname: Hasegawa
authors.affiliation: Department of Obstetrics and Gynaecology, Showa University School of Medicine, Tokyo, Japan.
authors.forename: T
authors.initials: T
authors.lastname: Arakaki
authors.affiliation: Department of Obstetrics and Gynaecology, Showa University School of Medicine, Tokyo, Japan.
authors.forename: H
authors.initials: H
authors.lastname: Takita
authors.affiliation: Department of Obstetrics and Gynaecology, Showa University School of Medicine, Tokyo, Japan.
authors.forename: T
authors.initials: T
authors.lastname: Oba
authors.affiliation: Department of Obstetrics and Gynaecology, Showa University School of Medicine, Tokyo, Japan.
authors.forename: M
authors.initials: M
authors.lastname: Nakamura
authors.affiliation: Department of Obstetrics and Gynaecology, Showa University School of Medicine, Tokyo, Japan.
authors.forename: A
authors.initials: A
authors.lastname: Sekizawa
mesh_terms: D000328:Adult; D002585:Cesarean Section / Q000009:adverse effects*; D005260:Female; D006801:Humans; D010923:Placenta Previa / Q000000981:diagnostic imaging*; D011247:Pregnancy; D011446:Prospective Studies; D016216:Ultrasonography, Prenatal; D014592:Uterine Hemorrhage / Q000209:etiology*; D014599:Uterus / Q000000981:diagnostic imaging / Q000502:physiology*
keywords: Atonic bleeding; Caesarean section; Haemorrhage; Placenta previa; Ultrasound; Uterine isthmus