title: Localization of the embryo in the lower part of the gestational sac at 6-7 weeks' gestation is associated with placenta previa.
abstract: OBJECTIVE
  To evaluate whether placenta previa is associated with ultrasonographic findings during the first trimester.
  
  
  METHODS
  A case-control study with 1:5 (34 and 170 cases with placenta previa and normal placenta) matched pairs was conducted to compare ultrasonographic findings, including the position of the gestational sac (GS), that of the embryo in the GS, and placental cord insertion from 5-11 weeks of gestation.
  
  
  RESULTS
  Embryos located in the lower part of the GS at 6-7 weeks of gestation were observed in 83.3 and 17.1% of the cases and the controls, respectively. Placental cord insertion in the lower third of the uterus at 9-11 weeks of gestation was observed in 38.3 and 6.7% of the cases and the controls, respectively.
  
  
  CONCLUSIONS
  Low embryo localization and low placental cord insertion during the first trimester was associated with placenta previa.
authors.affiliation: Department of Obstetrics and Gynecology, Showa University School of Medicine, 1-5-8 Hatanodai, Shinagawa-ku, Tokyo, Japan. hasejun@oak.dti.ne.jp
authors.forename: Junichi
authors.initials: J
authors.lastname: Hasegawa
authors.forename: Takashi
authors.initials: T
authors.lastname: Mimura
authors.forename: Shoko
authors.initials: S
authors.lastname: Hamada
authors.forename: Masamitsu
authors.initials: M
authors.lastname: Nakamura
authors.forename: Ryu
authors.initials: R
authors.lastname: Matsuoka
authors.forename: Kiyotake
authors.initials: K
authors.lastname: Ichizuka
authors.forename: Akihiko
authors.initials: A
authors.lastname: Sekizawa
authors.forename: Takashi
authors.initials: T
authors.lastname: Okai
mesh_terms: D000328:Adult; D004622:Embryo, Mammalian / Q000000981:diagnostic imaging*; D005260:Female; D005865:Gestational Age; D058746:Gestational Sac / Q000000981:diagnostic imaging*; D006801:Humans; D010923:Placenta Previa / Q000000981:diagnostic imaging*; D011247:Pregnancy; D011261:Pregnancy Trimester, First; D012189:Retrospective Studies; D016216:Ultrasonography, Prenatal; D014470:Umbilical Cord / Q000000981:diagnostic imaging