title: Improving the Accuracy of Diagnosing Placenta Previa on Transvaginal Ultrasound by Distinguishing between the Uterine Isthmus and Cervix: A Prospective Multicenter Observational Study.
abstract: OBJECTIVE
  To clarify whether distinguishing between the uterine isthmus and cervix can improve the accuracy of diagnosing placenta previa at term.
  
  
  METHODS
  A multicenter prospective observational study was conducted among pregnant women with suspected placenta previa at 20-24 weeks' gestation. Subjects were divided into the open isthmus group and closed isthmus group. The accuracy of diagnosing placenta previa at term was compared between the 2 groups.
  
  
  RESULTS
  We screened 9,341 patients, and 53 (0.6%) met the inclusion criteria. Nineteen cases with an open isthmus and 34 with a closed isthmus were followed. The accuracy for diagnosing placenta previa or a low-lying placenta at term was 94.7% in the open isthmus group and 26.5% in the closed isthmus group (p < 0.001). Elective or emergency Cesarean section was required in 100% of cases in the open isthmus group and 20.6% in the closed isthmus group (p < 0.001).
  
  
  CONCLUSIONS
  A high prediction rate of placenta previa was obtained by using transvaginal ultrasound at 20-24 weeks' gestation after the isthmus opened by carefully distinguishing between the cervix and isthmus.
authors.affiliation: Department of Obstetrics and Gynecology, St. Marianna University School of Medicine, Kanagawa, Japan.
authors.forename: Junichi
authors.initials: J
authors.lastname: Hasegawa
authors.forename: Ikuno
authors.initials: I
authors.lastname: Kawabata
authors.forename: Yoshiharu
authors.initials: Y
authors.lastname: Takeda
authors.forename: Hiroaki
authors.initials: H
authors.lastname: Aoki
authors.forename: Takehiko
authors.initials: T
authors.lastname: Fukami
authors.forename: Atsushi
authors.initials: A
authors.lastname: Tajima
authors.forename: Kei
authors.initials: K
authors.lastname: Miyakoshi
authors.forename: Katsufumi
authors.initials: K
authors.lastname: Otsuki
authors.forename: Norio
authors.initials: N
authors.lastname: Shinozuka
authors.forename: Yoshio
authors.initials: Y
authors.lastname: Matsuda
authors.forename: Mitsutoshi
authors.initials: M
authors.lastname: Iwashita
authors.forename: Takashi
authors.initials: T
authors.lastname: Okai
authors.forename: Akihito
authors.initials: A
authors.lastname: Nakai
mesh_terms: D000328:Adult; D002584:Cervix Uteri / Q000000981:diagnostic imaging*; D005260:Female; D006801:Humans; D010923:Placenta Previa / Q000000981:diagnostic imaging*; D011247:Pregnancy; D011263:Pregnancy Trimester, Third; D011446:Prospective Studies; D012680:Sensitivity and Specificity; D016216:Ultrasonography, Prenatal / Q000379:methods*; D014599:Uterus / Q000000981:diagnostic imaging*