title: Abnormally shaped placentae in twin pregnancy.
abstract: OBJECTIVE
  We examined the incidence of abnormally shaped placentae such as circumvallate placenta and succenturiate lobes of placenta and their complications in twin compared with singleton pregnancies.
  
  
  METHODS
  A retrospective cohort study was performed with 592 (174 monochorionic and 418 dichorionic) twin and 11,311 singleton pregnancies managed at our hospital between 2000 and 2007.
  
  
  RESULTS
  There was no measurable difference in the incidence of circumvallate placenta between twin and singleton pregnancies (1.2% vs. 1.9%), while the incidence of succenturiate lobes of placenta in twin pregnancies was significantly higher than that in singleton pregnancies (1.5% vs. 0.73%, P = 0.033). In singleton pregnancies, the incidences of placental complications such as placental abruption, vasa previa and retained placenta were observed to be associated with the presence of abnormally shaped placentae. In the twin pregnancies, however, there were no relation between the incidences of placental complications and the presence of abnormally shaped placentae.
  
  
  CONCLUSIONS
  Succenturiate lobes of placenta were more common in twin pregnancies compared with singleton pregnancies. However, the presence of abnormally shaped placentae does not seem to affect perinatal outcomes in twin pregnancies.
authors.affiliation: Department of Obstetrics and Gynecology, Japanese Red Cross Katsushika Maternity Hospital, 5-11-12 Tateishi, Katsushika-ku, Tokyo, Japan. czg83542@mopera.ne.jp
authors.forename: Shunji
authors.initials: S
authors.lastname: Suzuki
authors.forename: Miwa
authors.initials: M
authors.lastname: Igarashi
authors.forename: Yusuke
authors.initials: Y
authors.lastname: Inde
authors.forename: Hidehiko
authors.initials: H
authors.lastname: Miyake